RMD-QOSM: The NSIS Quality-of-Service Model for Resource Management in Diffserv
RFC 5977
| Document | Type |
RFC - Experimental
(October 2010)
Was
draft-ietf-nsis-rmd
(nsis WG)
|
|
|---|---|---|---|
| Authors | Cornelia Kappler , Lars Westberg , Thomas R. Phelan , Georgios Karagiannis , Attila Bader | ||
| Last updated | 2015-10-14 | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | RFC 5977 (Experimental) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Lars Eggert | ||
| Send notices to | (None) |
RFC 5977
Internet Engineering Task Force (IETF) A. Bader
Request for Comments: 5977 L. Westberg
Category: Experimental Ericsson
ISSN: 2070-1721 G. Karagiannis
University of Twente
C. Kappler
ck technology concepts
T. Phelan
Sonus
October 2010
RMD-QOSM: The NSIS Quality-of-Service Model
for Resource Management in Diffserv
Abstract
This document describes a Next Steps in Signaling (NSIS) Quality-of-
Service (QoS) Model for networks that use the Resource Management in
Diffserv (RMD) concept. RMD is a technique for adding admission
control and preemption function to Differentiated Services (Diffserv)
networks. The RMD QoS Model allows devices external to the RMD
network to signal reservation requests to Edge nodes in the RMD
network. The RMD Ingress Edge nodes classify the incoming flows into
traffic classes and signals resource requests for the corresponding
traffic class along the data path to the Egress Edge nodes for each
flow. Egress nodes reconstitute the original requests and continue
forwarding them along the data path towards the final destination.
In addition, RMD defines notification functions to indicate overload
situations within the domain to the Edge nodes.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5977.
Bader, et al. Experimental [Page 1]
RFC 5977 RMD-QOSM October 2010
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................4
2. Terminology .....................................................6
3. Overview of RMD and RMD-QOSM ....................................7
3.1. RMD ........................................................7
3.2. Basic Features of RMD-QOSM ................................10
3.2.1. Role of the QNEs ...................................10
3.2.2. RMD-QOSM/QoS-NSLP Signaling ........................11
3.2.3. RMD-QOSM Applicability and Considerations ..........13
4. RMD-QOSM, Detailed Description .................................15
4.1. RMD-QSPEC Definition ......................................16
4.1.1. RMD-QOSM <QoS Desired> and <QoS Reserved> ..........16
4.1.2. PHR Container ......................................17
4.1.3. PDR Container ......................................20
4.2. Message Format ............................................23
4.3. RMD Node State Management .................................23
4.3.1. Aggregated Operational and Reservation
States at the QNE Edges ............................23
4.3.2. Measurement-Based Method ...........................25
4.3.3. Reservation-Based Method ...........................27
4.4. Transport of RMD-QOSM Messages ............................28
4.5. Edge Discovery and Message Addressing .....................31
4.6. Operation and Sequence of Events ..........................32
4.6.1. Basic Unidirectional Operation .....................32
4.6.1.1. Successful Reservation ....................34
4.6.1.2. Unsuccessful Reservation ..................46
4.6.1.3. RMD Refresh Reservation ...................50
4.6.1.4. RMD Modification of Aggregated
Reservations ..............................54
4.6.1.5. RMD Release Procedure .....................55
4.6.1.6. Severe Congestion Handling ................64
Bader, et al. Experimental [Page 2]
RFC 5977 RMD-QOSM October 2010
4.6.1.7. Admission Control Using Congestion
Notification Based on Probing .............70
4.6.2. Bidirectional Operation ............................73
4.6.2.1. Successful and Unsuccessful Reservations ..77
4.6.2.2. Refresh Reservations ......................82
4.6.2.3. Modification of Aggregated Intra-Domain
QoS-NSLP Operational Reservation States ...82
4.6.2.4. Release Procedure .........................83
4.6.2.5. Severe Congestion Handling ................84
4.6.2.6. Admission Control Using Congestion
Notification Based on Probing .............87
4.7. Handling of Additional Errors .............................89
5. Security Considerations ........................................89
5.1. Introduction ..............................................89
5.2. Security Threats ..........................................91
5.2.1. On-Path Adversary ..................................92
5.2.2. Off-Path Adversary .................................94
5.3. Security Requirements .....................................94
5.4. Security Mechanisms .......................................94
6. IANA Considerations ............................................97
6.1. Assignment of QSPEC Parameter IDs .........................97
7. Acknowledgments ................................................97
8. References .....................................................97
8.1. Normative References ......................................97
8.2. Informative References ....................................98
Appendix A. Examples .............................................101
A.1. Example of a Re-Marking Operation during Severe
Congestion in the Interior Nodes .........................101
A.2. Example of a Detailed Severe Congestion Operation in the
Egress Nodes .............................................107
A.3. Example of a Detailed Re-Marking Admission Control
(Congestion Notification) Operation in Interior Nodes ....111
A.4. Example of a Detailed Admission Control (Congestion
Notification) Operation in Egress Nodes ..................112
A.5. Example of Selecting Bidirectional Flows for Termination
during Severe Congestion .................................113
A.6. Example of a Severe Congestion Solution for
Bidirectional Flows Congested Simultaneously on Forward
and Reverse Paths ........................................113
A.7. Example of Preemption Handling during Admission Control ..117
A.8. Example of a Retransmission Procedure within the RMD
Domain ...................................................120
A.9. Example on Matching the Initiator QSPEC to the Local
RMD-QSPEC ................................................122
Bader, et al. Experimental [Page 3]
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1. Introduction
This document describes a Next Steps in Signaling (NSIS) QoS Model
for networks that use the Resource Management in Diffserv (RMD)
framework ([RMD1], [RMD2], [RMD3], and [RMD4]). RMD adds admission
control to Diffserv networks and allows nodes external to the
networks to dynamically reserve resources within the Diffserv
domains.
The Quality-of-Service NSIS Signaling Layer Protocol (QoS-NSLP)
[RFC5974] specifies a generic protocol for carrying QoS signaling
information end-to-end in an IP network. Each network along the end-
to-end path is expected to implement a specific QoS Model (QOSM)
specified by the QSPEC template [RFC5975] that interprets the
requests and installs the necessary mechanisms, in a manner that is
appropriate to the technology in use in the network, to ensure the
delivery of the requested QoS. This document specifies an NSIS QoS
Model for RMD networks (RMD-QOSM), and an RMD-specific QSPEC (RMD-
QSPEC) for expressing reservations in a suitable form for simple
processing by internal nodes.
They are used in combination with the QoS-NSLP to provide QoS
signaling service in an RMD network. Figure 1 shows an RMD network
with the respective entities.
Stateless or reduced-state Egress
Ingress RMD Nodes Node
Node (Interior Nodes; I-Nodes) (Stateful
(Stateful | | | RMD QoS
RMD QoS-NLSP | | | NSLP Node)
Node) V V V
+-------+ Data +------+ +------+ +------+ +------+
|-------|--------|------|------|------|-------|------|---->|------|
| | Flow | | | | | | | |
|Ingress| |I-Node| |I-Node| |I-Node| |Egress|
| | | | | | | | | |
+-------+ +------+ +------+ +------+ +------+
=================================================>
<=================================================
Signaling Flow
Figure 1: Actors in the RMD-QOSM
Many network scenarios, such as the "Wired Part of Wireless Network"
scenario, which is described in Section 8.4 of [RFC3726], require
that the impact of the used QoS signaling protocol on the network
performance should be minimized. In such network scenarios, the
performance of each network node that is used in a communication path
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has an impact on the end-to-end performance. As such, the end-to-end
performance of the communication path can be improved by optimizing
the performance of the Interior nodes. One of the factors that can
contribute to this optimization is the minimization of the QoS
signaling protocol processing load and the minimization of the number
of states on each Interior node.
Another requirement that is imposed by such network scenarios is that
whenever a severe congestion situation occurs in the network, the
used QoS signaling protocol should be able to solve them. In the
case of a route change or link failure, a severe congestion situation
may occur in the network. Typically, routing algorithms are able to
adapt and change their routing decisions to reflect changes in the
topology and traffic volume. In such situations, the rerouted
traffic will have to follow a new path. Interior nodes located on
this new path may become overloaded, since they suddenly might need
to support more traffic than for which they have capacity. These
severe congestion situations will severely affect the overall
performance of the traffic passing through such nodes.
RMD-QOSM is an edge-to-edge (intra-domain) QoS Model that, in
combination with the QoS-NSLP and QSPEC specifications, is designed
to support the requirements mentioned above:
o Minimal impact on Interior node performance;
o Increase of scalability;
o Ability to deal with severe congestion
Internally to the RMD network, RMD-QOSM together with QoS-NSLP
[RFC5974] defines a scalable QoS signaling model in which per-flow
QoS-NSLP and NSIS Transport Layer Protocol (NTLP) states are not
stored in Interior nodes but per-flow signaling is performed (see
[RFC5974]) at the Edges.
In the RMD-QOSM, only routers at the Edges of a Diffserv domain
(Ingress and Egress nodes) support the (QoS-NSLP) stateful operation;
see Section 4.7 of [RFC5974]. Interior nodes support either the
(QoS-NSLP) stateless operation or a reduced-state operation with
coarser granularity than the Edge nodes.
After the terminology in Section 2, we give an overview of RMD and
the RMD-QOSM in Section 3. This document specifies several RMD-QOSM/
QoS-NSLP signaling schemes. In particular, Section 3.2.3 identifies
which combination of sections are used for the specification of each
RMD-QOSM/QoS-NSLP signaling scheme. In Section 4 we give a detailed
description of the RMD-QOSM, including the role of QoS NSIS entities
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(QNEs), the definition of the QSPEC, mapping of QSPEC generic
parameters onto RMD-QOSM parameters, state management in QNEs, and
operation and sequence of events. Section 5 discusses security
issues.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminology defined by GIST [RFC5971] and QoS-NSLP [RFC5974]
applies to this document.
In addition, the following terms are used:
NSIS domain: an NSIS signaling-capable domain.
RMD domain: an NSIS domain that is capable of supporting the RMD-QOSM
signaling and operations.
Edge node: a QoS-NSLP node on the boundary of some administrative
domain that connects one NSIS domain to a node in either another NSIS
domain or a non-NSIS domain.
NSIS-aware node: a node that is aware of NSIS signaling and RMD-QOSM
operations, such as severe congestion detection and Differentiated
Service Code Point (DSCP) marking.
NSIS-unaware node: a node that is unaware of NSIS signaling, but is
aware of RMD-QOSM operations such as severe congestion detection and
DSCP marking.
Ingress node: an Edge node in its role in handling the traffic as it
enters the NSIS domain.
Egress node: an Edge node in its role in handling the traffic as it
leaves the NSIS domain.
Interior node: a node in an NSIS domain that is not an Edge node.
Congestion: a temporal network state that occurs when the traffic (or
when traffic associated with a particular Per-Hop Behavior (PHB))
passing through a link is slightly higher than the capacity allocated
for the link (or allocated for the particular PHB). If no measures
are taken, then the traffic passing through this link may temporarily
slightly degrade in QoS. This type of congestion is usually solved
using admission control mechanisms.
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Severe congestion: the congestion situation on a particular link
within the RMD domain where a significant increase in its real packet
queue situation occurs, such as when due to a link failure rerouted
traffic has to be supported by this particular link.
3. Overview of RMD and RMD-QOSM
3.1. RMD
The Differentiated Services (Diffserv) architecture ([RFC2475],
[RFC2638]) was introduced as a result of efforts to avoid the
scalability and complexity problems of IntServ [RFC1633].
Scalability is achieved by offering services on an aggregate rather
than per-flow basis and by forcing as much of the per-flow state as
possible to the Edges of the network. The service differentiation is
achieved using the Differentiated Services (DS) field in the IP
header and the Per-Hop Behavior (PHB) as the main building blocks.
Packets are handled at each node according to the PHB indicated by
the DS field in the message header.
The Diffserv architecture does not specify any means for devices
outside the domain to dynamically reserve resources or receive
indications of network resource availability. In practice, service
providers rely on short active time Service Level Agreements (SLAs)
that statically define the parameters of the traffic that will be
accepted from a customer.
RMD was introduced as a method for dynamic reservation of resources
within a Diffserv domain. It describes a method that is able to
provide admission control for flows entering the domain and a
congestion handling algorithm that is able to terminate flows in case
of congestion due to a sudden failure (e.g., link, router) within the
domain.
In RMD, scalability is achieved by separating a fine-grained
reservation mechanism used in the Edge nodes of a Diffserv domain
from a much simpler reservation mechanism needed in the Interior
nodes. Typically, it is assumed that Edge nodes support per-flow QoS
states in order to provide QoS guarantees for each flow. Interior
nodes use only one aggregated reservation state per traffic class or
no states at all. In this way, it is possible to handle large
numbers of flows in the Interior nodes. Furthermore, due to the
limited functionality supported by the Interior nodes, this solution
allows fast processing of signaling messages.
The possible RMD-QOSM applicabilities are described in Section 3.2.3.
Two main basic admission control modes are supported: reservation-
based and measurement-based admission control that can be used in
Bader, et al. Experimental [Page 7]
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combination with a severe congestion-handling solution. The severe
congestion-handling solution is used in the situation that a
link/node becomes severely congested due to the fact that the traffic
supported by a failed link/node is rerouted and has to be processed
by this link/node. Furthermore, RMD-QOSM supports both
unidirectional and bidirectional reservations.
Another important feature of RMD-QOSM is that the intra-domain
sessions supported by the Edges can be either per-flow sessions or
per-aggregate sessions. In the case of the per-flow intra-domain
sessions, the maintained per-flow intra-domain states have a one-to-
one dependency to the per-flow end-to-end states supported by the
same Edge. In the case of the per-aggregate sessions the maintained
per-aggregate states have a one-to-many relationship to the per-flow
end-to-end states supported by the same Edge.
In the reservation-based method, each Interior node maintains only
one reservation state per traffic class. The Ingress Edge nodes
aggregate individual flow requests into PHB traffic classes, and
signal changes in the class reservations as necessary. The
reservation is quantified in terms of resource units (or bandwidth).
These resources are requested dynamically per PHB and reserved on
demand in all nodes in the communication path from an Ingress node to
an Egress node.
The measurement-based algorithm continuously measures traffic levels
and the actual available resources, and admits flows whose resource
needs are within what is available at the time of the request. The
measurement-based algorithm is used to support a predictive service
where the service commitment is somewhat less reliable than the
service that can be supported by the reservation-based method.
A main assumption that is made by such measurement-based admission
control mechanisms is that the aggregated PHB traffic passing through
an RMD Interior node is high and therefore, current measurement
characteristics are considered to be an indicator of future load.
Once an admission decision is made, no record of the decision need be
kept at the Interior nodes. The advantage of measurement-based
resource management protocols is that they do not require pre-
reservation state nor explicit release of the reservations at the
Interior nodes. Moreover, when the user traffic is variable,
measurement-based admission control could provide higher network
utilization than, e.g., peak-rate reservation. However, this can
introduce an uncertainty in the availability of the resources. It is
important to emphasize that the RMD measurement-based schemes
described in this document do not use any refresh procedures, since
these approaches are used in stateless nodes; see Section 4.6.1.3.
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Two types of measurement-based admission control schemes are
possible:
* Congestion notification function based on probing:
This method can be used to implement a simple measurement-based
admission control within a Diffserv domain. In this scenario, the
Interior nodes are not NSIS-aware nodes. In these Interior nodes,
thresholds are set for the traffic belonging to different PHBs in the
measurement-based admission control function. In this scenario, an
end-to-end NSIS message is used as a probe packet, meaning that the
<DSCP> field in the header of the IP packet that carries the NSIS
message is re-marked when the predefined congestion threshold is
exceeded. Note that when the predefined congestion threshold is
exceeded, all packets are re-marked by a node, including NSIS
messages. In this way, the Edges can admit or reject flows that are
requesting resources. The frequency and duration that the congestion
level is above the threshold resulting in re-marking is tracked and
used to influence the admission control decisions.
* NSIS measurement-based admission control:
In this case, the measurement-based admission control functionality
is implemented in NSIS-aware stateless routers. The main difference
between this type of admission control and the congestion
notification based on probing is related to the fact that this type
of admission control is applied mainly on NSIS-aware nodes. With the
measurement-based scheme, the requested peak bandwidth of a flow is
carried by the admission control request. The admission decision is
considered as positive if the currently carried traffic, as
characterized by the measured statistics, plus the requested
resources for the new flow exceeds the system capacity with a
probability smaller than a value alpha. Otherwise, the admission
decision is negative. It is important to emphasize that due to the
fact that the RMD Interior nodes are stateless, they do not store
information of previous admission control requests.
This could lead to a situation where the admission control accuracy
is decreased when multiple simultaneous flows (sharing a common
Interior node) are requesting admission control simultaneously. By
applying measuring techniques, e.g., see [JaSh97] and [GrTs03], which
use current and past information on NSIS sessions that requested
resources from an NSIS-aware Interior node, the decrease in admission
control accuracy can be limited. RMD describes the following
procedures:
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* classification of an individual resource reservation or a resource
query into Per-Hop Behavior (PHB) groups at the Ingress node of the
domain,
* hop-by-hop admission control based on a PHB within the domain.
There are two possible modes of operation for internal nodes to
admit requests. One mode is the stateless or measurement-based
mode, where the resources within the domain are queried. Another
mode of operation is the reduced-state reservation or reservation-
based mode, where the resources within the domain are reserved.
* a method to forward the original requests across the domain up to
the Egress node and beyond.
* a congestion-control algorithm that notifies the Egress Edge nodes
about congestion. It is able to terminate the appropriate number
of flows in the case a of congestion due to a sudden failure (e.g.,
link or router failure) within the domain.
3.2. Basic Features of RMD-QOSM
3.2.1. Role of the QNEs
The protocol model of the RMD-QOSM is shown in Figure 2. The figure
shows QoS NSIS initiator (QNI) and QoS NSIS Receiver (QNR) nodes, not
part of the RMD network, that are the ultimate initiator and receiver
of the QoS reservation requests. It also shows QNE nodes that are
the Ingress and Egress nodes in the RMD domain (QNE Ingress and QNE
Egress), and QNE nodes that are Interior nodes (QNE Interior).
All nodes of the RMD domain are usually QoS-NSLP-aware nodes.
However, in the scenarios where the congestion notification function
based on probing is used, then the Interior nodes are not NSIS aware.
Edge nodes store and maintain QoS-NSLP and NTLP states and therefore
are stateful nodes. The NSIS-aware Interior nodes are NTLP
stateless. Furthermore, they are either QoS-NSLP stateless (for NSIS
measurement-based operation) or reduced-state nodes storing per PHB
aggregated QoS-NSLP states (for reservation-based operation).
Note that the RMD domain MAY contain Interior nodes that are not
NSIS-aware nodes (not shown in the figure).
These nodes are assumed to have sufficient capacity for flows that
might be admitted. Furthermore, some of these NSIS-unaware nodes MAY
be used for measuring the traffic congestion level on the data path.
These measurements can be used by RMD-QOSM in the congestion control
based on probing operation and/or severe congestion operation (see
Section 4.6.1.6).
Bader, et al. Experimental [Page 10]
RFC 5977 RMD-QOSM October 2010
|------| |-------| |------| |------|
| e2e |<->| e2e |<------------------------->| e2e |<->| e2e |
| QoS | | QoS | | QoS | | QoS |
| | |-------| |------| |------|
| | |-------| |-------| |-------| |------| | |
| | | local |<->| local |<->| local |<->| local| | |
| | | QoS | | QoS | | QoS | | QoS | | |
| | | | | | | | | | | |
| NSLP | | NSLP | | NSLP | | NSLP | | NSLP | | NSLP |
|st.ful| |st.ful | |st.less/ |st.less/ |st.ful| |st.ful|
| | | | |red.st.| |red.st.| | | | |
| | |-------| |-------| |-------| |------| | |
|------| |-------| |-------| |-------| |------| |------|
------------------------------------------------------------------
|------| |-------| |-------| |-------| |------| |------|
| NTLP |<->| NTLP |<->| NTLP |<->| NTLP |<->| NTLP |<->|NTLP |
|st.ful| |st.ful | |st.less| |st.less| |st.ful| |st.ful|
|------| |-------| |-------| |-------| |------| |------|
QNI QNE QNE QNE QNE QNR
(End) (Ingress) (Interior) (Interior) (Egress) (End)
st.ful: stateful, st.less: stateless
st.less red.st.: stateless or reduced-state
Figure 2: Protocol model of stateless/reduced-state operation
3.2.2. RMD-QOSM/QoS-NSLP Signaling
The basic RMD-QOSM/QoS-NSLP signaling is shown in Figure 3. The
signaling scenarios are accomplished using the QoS-NSLP processing
rules defined in [RFC5974], in combination with the Resource
Management Function (RMF) triggers sent via the QoS-NSLP-RMF API
described in [RFC5974].
Due to the fact that within the RMD domain a QoS Model that is
different than the end-to-end QoS Model applied at the Edges of the
RMD domain can be supported, the RMD Interior node reduced-state
reservations can be updated independently of the per-flow end-to-end
reservations (see Section 4.7 of [RFC5974]). Therefore, two
different RESERVE messages are used within the RMD domain. One
RESERVE message that is associated with the per-flow end-to-end
reservations and is used by the Edges of the RMD domain and one that
is associated with the reduced-state reservations within the RMD
domain.
A RESERVE message is created by a QNI with an Initiator QSPEC
describing the reservation and forwarded along the path towards the
QNR.
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When the original RESERVE message arrives at the Ingress node, an
RMD-QSPEC is constructed based on the initial QSPEC in the message
(usually the Initiator QSPEC). The RMD-QSPEC is sent in a intra-
domain, independent RESERVE message through the Interior nodes
towards the QNR. This intra-domain RESERVE message uses the GIST
datagram signaling mechanism. Note that the RMD-QOSM cannot directly
specify that the GIST Datagram mode SHOULD be used. This can however
be notified by using the GIST API Transfer-Attributes, such as
unreliable, low level of security and use of local policy.
Meanwhile, the original RESERVE message is sent to the Egress node on
the path to the QNR using the reliable transport mode of NTLP. Each
QoS-NSLP node on the data path processes the intra-domain RESERVE
message and checks the availability of resources with either the
reservation-based or the measurement-based method.
QNE Ingress QNE Interior QNE Interior QNE Egress
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
RESERVE | | | |
-------->| RESERVE | | |
+--------------------------------------------->|
| RESERVE' | | |
+-------------->| | |
| | RESERVE' | |
| +-------------->| |
| | | RESERVE' |
| | +------------->|
| | | RESPONSE'|
|<---------------------------------------------+
| | | | RESERVE
| | | +------->
| | | |RESPONSE
| | | |<-------
| | | RESPONSE |
|<---------------------------------------------+
RESPONSE| | | |
<--------| | | |
Figure 3: Sender-initiated reservation with reduced-state
Interior nodes
When the message reaches the Egress node, and the reservation is
successful in each Interior node, an intra-domain (local) RESPONSE'
is sent towards the Ingress node and the original (end-to-end)
RESERVE message is forwarded to the next domain. When the Egress
node receives a RESPONSE message from the downstream end, it is
forwarded directly to the Ingress node.
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If an intermediate node cannot accommodate the new request, it
indicates this by marking a single bit in the message, and continues
forwarding the message until the Egress node is reached. From the
Egress node, an intra-domain RESPONSE' and an original RESPONSE
message are sent directly to the Ingress node.
As a consequence, in the stateless/reduced-state domain only sender-
initiated reservations can be performed and functions requiring per-
flow NTLP or QoS-NSLP states, like summary and reduced refreshes,
cannot be used. If per-flow identification is needed, i.e.,
associating the flow IDs for the reserved resources, Edge nodes act
on behalf of Interior nodes.
3.2.3. RMD-QOSM Applicability and Considerations
The RMD-QOSM is a Diffserv-based bandwidth management methodology
that is not able to provide a full Diffserv support. The reason for
this is that the RMD-QOSM concept can only support the (Expedited
Forwarding) EF-like functionality behavior, but is not able to
support the full set of (Assured Forwarding) AF-like functionality.
The bandwidth information REQUIRED by the EF-like functionality
behavior can be supported by RMD-QOSM carrying the bandwidth
information in the <QoS Desired> parameter (see [RFC5975]). The full
set of (Assured Forwarding) AF-like functionality requires
information that is specified in two token buckets. The RMD-QOSM is
not supporting the use of two token buckets and therefore, it is not
able to support the full set of AF-functionality. Note however, that
RMD-QOSM could also support a single AF PHB, when the traffic or the
upper limit of the traffic can be characterized by a single bandwidth
parameter. Moreover, it is considered that in case of tunneling, the
RMD-QOSM supports only the uniform tunneling mode for Diffserv (see
[RFC2983]).
The RMD domain MUST be engineered in such a way that each QNE Ingress
maintains information about the smallest MTU that is supported on the
links within the RMD domain.
A very important consideration on using RMD-QOSM is that within one
RMD domain only one of the following RMD-QOSM schemes can be used at
a time. Thus, an RMD router can never process and use two different
RMD-QOSM signaling schemes at the same time.
However, all RMD QNEs supporting this specification MUST support the
combination of the "per-flow RMD reservation-based" and the "severe
congestion handling by proportional data packet marking" scheme. If
the RMD QNEs support more RMD-QOSM schemes, then the operator of that
RMD domain MUST preconfigure all the QNE Edge nodes within one domain
such that the <SCH> field included in the "PHR container" (Section
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4.1.2) and the "PDR Container" (Section 4.1.3) will always use the
same value, such that within one RMD domain only one of the below
described RMD-QOSM schemes is used at a time.
The congestion situations (see Section 2) are solved using an
admission control mechanism, e.g., "per-flow congestion notification
based on probing", while the severe congestion situations (see
Section 2), are solved using the severe congestion handling
mechanisms, e.g., "severe congestion handling by proportional data
packet marking".
The RMD domain MUST be engineered in such a way that RMD-QOSM
messages could be transported using the GIST Query and DATA messages
in Q-mode; see [RFC5971]. This means that the Path MTU MUST be
engineered in such a way that the RMD-QOSM message are transported
without fragmentation. Furthermore, the RMD domain MUST be
engineered in such a way to guarantee capacity for the GIST Query and
Data messages in Q-mode, within the rate control limits imposed by
GIST; see [RFC5971].
The RMD domain has to be configured such that the GIST context-free
flag (C-flag) MUST be set (C=1) for QUERY messages and DATA messages
sent in Q-mode; see [RFC5971].
Moreover, the same deployment issues and extensibility considerations
described in [RFC5971] and [RFC5978] apply to this document.
It is important to note that the concepts described in Sections
4.6.1.6.2, 4.6.2.5.2, 4.6.1.6.2, and 4.6.2.5.2 contributed to the PCN
WG standardization.
The available RMD-QOSM/QoS-NSLP signaling schemes are:
* "per-flow congestion notification based on probing" (see Sections
4.3.2, 4.6.1.7, and 4.6.2.6). Note that this scheme uses, for
severe congestion handling, the "severe congestion handling by
proportional data packet marking" (see Sections 4.6.1.6.2 and
4.6.2.5.2). Furthermore, the Interior nodes are considered to be
Diffserv aware, but NSIS-unaware nodes (see Section 4.3.2).
* "per-flow RMD NSIS measurement-based admission control" (see
Sections 4.3.2, 4.6.1, and 4.6.2). Note that this scheme uses, for
severe congestion handling, the "severe congestion handling by
proportional data packet marking" (see Sections 4.6.1.6.2 and
4.6.2.5.2). Furthermore, the Interior nodes are considered to be
NSIS-aware nodes (see Section 4.3.2).
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* "per-flow RMD reservation-based" in combination with the "severe
congestion handling by the RMD-QOSM refresh" procedure (see
Sections 4.3.3, 4.6.1, 4.6.1.6.1, and 4.6.2.5.1). Note that this
scheme uses, for severe congestion handling, the "severe congestion
handling by the RMD-QOSM refresh" procedure (see Sections 4.6.1.6.1
and 4.6.2.5.1). Furthermore, the intra-domain sessions supported
by the Edge nodes are per-flow sessions (see Section 4.3.3).
* "per-flow RMD reservation-based" in combination with the "severe
the congestion handling by proportional data packet marking"
procedure (see Sections 4.3.3, 4.6.1, 4.6.1.6.2, and 4.6.2.5.2).
Note that this scheme uses, for severe congestion handling, the
"severe congestion handling by proportional data packet marking"
procedure (see Sections 4.6.1.6.2 and 4.6.2.5.2). Furthermore, the
intra-domain sessions supported by the Edge nodes are per-flow
sessions (see Section 4.3.3).
* "per-aggregate RMD reservation-based" in combination with the
"severe congestion handling by the RMD-QOSM refresh" procedure (see
Sections 4.3.1, 4.6.1, 4.6.1.6.1, and 4.6.2.5.1). Note that this
scheme uses, for severe congestion handling, the "severe congestion
handling by the RMD-QOSM refresh" procedure (see Sections 4.6.1.6.1
and 4.6.2.5.1). Furthermore, the intra-domain sessions supported
by the Edge nodes are per-aggregate sessions (see Section 4.3.1).
Moreover, this scheme can be considered to be a reservation-based
scheme, since the RMD Interior nodes are reduced-state nodes, i.e.,
they do not store NTLP/GIST states, but they do store per PHB-
aggregated QoS-NSLP reservation states.
* "per-aggregate RMD reservation-based" in combination with the
"severe congestion handling by proportional data packet marking"
procedure (see Sections 4.3.1, 4.6.1, 4.6.1.6.2, and 4.6.2.5.2).
Note that this scheme uses, for severe congestion handling, the
"severe congestion handling by proportional data packet marking"
procedure (see Sections 4.6.1.6.2 and 4.6.2.5.2). Furthermore, the
intra-domain sessions supported by the Edge nodes are per-aggregate
sessions (see Section 4.3.1). Moreover, this scheme can be
considered to be a reservation-based scheme, since the RMD Interior
nodes are reduced-state nodes, i.e., they do not store NTLP/GIST
states, but they do store per PHB-aggregated QoS-NSLP reservation
states.
4. RMD-QOSM, Detailed Description
This section describes the RMD-QOSM in more detail. In particular,
it defines the role of stateless and reduced-state QNEs, the RMD-QOSM
QSPEC Object, the format of the RMD-QOSM QoS-NSLP messages, and how
QSPECs are processed and used in different protocol operations.
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4.1. RMD-QSPEC Definition
The RMD-QOSM uses the QSPEC format specified in [RFC5975]. The
Initiator/Local QSPEC bit, i.e., <I> is set to "Local" (i.e., "1")
and the <QSPEC Proc> is set as follows:
* Message Sequence = 0: Sender initiated
* Object combination = 0: <QoS Desired> for RESERVE and
<QoS Reserved> for RESPONSE
The <QSPEC Version> used by RMD-QOSM is the default version, i.e.,
"0", see [RFC5975]. The <QSPEC Type> value used by the RMD-QOSM is
specified in [RFC5975] and is equal to "2". The <Traffic Handling
Directives> contains the following fields:
<Traffic Handling Directives> = <PHR container> <PDR container>
The Per-Hop Reservation container (PHR container) and the Per-Domain
Reservation container (PDR container) are specified in Sections 4.1.2
and 4.1.3, respectively. The <PHR container> contains the traffic
handling directives for intra-domain communication and reservation.
The <PDR container> contains additional traffic handling directives
that are needed for edge-to-edge communication. The parameter IDs
used by the <PHR container> and <PDR container> are assigned by IANA;
see Section 6.
The RMD-QOSM <QoS Desired> and <QoS Reserved>, are specified in
Section 4.1.1. The RMD-QOSM <QoS Desired> and <QoS Reserved> and the
<PHR container> are used and processed by the Edge and Interior
nodes. The <PDR container> field is only processed by Edge nodes.
4.1.1. RMD-QOSM <QoS Desired> and <QoS Reserved>
The RESERVE message contains only the <QoS Desired> object [RFC5975].
The <QoS Reserved> object is carried by the RESPONSE message.
In RMD-QOSM, the <QoS Desired> and <QoS Reserved> objects contain the
following parameters:
<QoS Desired> = <TMOD-1> <PHB Class> <Admission Priority>
<QoS Reserved> = <TMOD-1> <PHB Class> <Admission Priority>
The bit format of the <PHB Class> (see [RFC5975] and Figures 4 and 5)
and <Admission Priority> complies with the bit format specified in
[RFC5975].
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Note that for the RMD-QOSM, a reservation established without an
<Admission Priority> parameter is equivalent to a reservation
established with an <Admission Priority> whose value is 1.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSCP |0 0 0 0 0 0 0 0 X 0|
+---+---+---+---+---+---+---+---+
Figure 4: DSCP parameter
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PHB ID code |0 0 X X|
+---+---+---+---+---+---+---+---+
Figure 5: PHB ID Code parameter
4.1.2. PHR Container
This section describes the parameters used by the PHR container,
which are used by the RMD-QOSM functionality available at the
Interior nodes.
<PHR container> = <O> <K> <S> <M>, <Admitted Hops>, <B> <Hop_U> <Time
Lag> <SCH> <Max Admitted Hops>
The bit format of the PHR container can be seen in Figure 6. Note
that in Figure 6 <Hop_U> is represented as <U>. Furthermore, in
Figure 6, <Max Admitted Hops> is represented as <Max Adm Hops>.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|E|N|r| Parameter ID |r|r|r|r| 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|M| Admitted Hops|B|U| Time Lag |O|K| SCH | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Adm Hops | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: PHR container
Parameter ID: 12-bit field, indicating the PHR type:
PHR_Resource_Request, PHR_Release_Request, PHR_Refresh_Update.
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"PHR_Resource_Request" (Parameter ID = 17): initiate or update the
traffic class reservation state on all nodes located on the
communication path between the QNE(Ingress) and QNE(Egress) nodes.
"PHR_Release_Request" (Parameter ID = 18): explicitly release, by
subtraction, the reserved resources for a particular flow from a
traffic class reservation state.
"PHR_Refresh_Update" (Parameter ID = 19): refresh the traffic class
reservation soft state on all nodes located on the communication path
between the QNE(Ingress) and QNE(Egress) nodes according to a
resource reservation request that was successfully processed during a
previous refresh period.
<S> (Severe Congestion): 1 bit. In the case of a route change,
refreshing RESERVE messages follow the new data path, and hence
resources are requested there. If the resources are not sufficient
to accommodate the new traffic, severe congestion occurs. Severe
congested Interior nodes SHOULD notify Edge QNEs about the congestion
by setting the <S> bit.
<O> (Overload): 1 bit. This field is used during the severe
congestion handling scheme that is using the RMD-QOSM refresh
procedure. This bit is set when an overload on a QNE Interior node
is detected and when this field is carried by the
"PHR_Refresh_Update" container. <O> SHOULD be set to"1" if the <S>
bit is set. For more details, see Section 4.6.1.6.1.
<M>: 1 bit. In the case of unsuccessful resource reservation or
resource query in an Interior QNE, this QNE sets the <M> bit in order
to notify the Egress QNE.
<Admitted Hops>: 8-bit field. The <Admitted Hops> counts the number
of hops in the RMD domain where the reservation was successful. The
<Admitted Hops> is set to "0" when a RESERVE message enters a domain
and it MUST be incremented by each Interior QNE, provided that the
<Hop_U> bit is not set. However, when a QNE that does not have
sufficient resources to admit the reservation is reached, the <M> bit
is set, and the <Admitted Hops> value is frozen, by setting the
<Hop_U> bit to "1". Note that the <Admitted Hops> parameter in
combination with the <Max Admitted Hops> and <K> parameters are used
during the RMD partial release procedures (see Section 4.6.1.5.2).
<Hop_U> (NSLP_Hops unset): 1 bit. The QNE(Ingress) node MUST set the
<Hop_U> parameter to 0. This parameter SHOULD be set to "1" by a
node when the node does not increase the <Admitted Hops> value. This
is the case when an RMD-QOSM reservation-based node is not admitting
the reservation request. When <Hop_U> is set to "1", the <Admitted
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Hops> SHOULD NOT be changed. Note that this flag, in combination
with the <Admitted Hops> flag, are used to locate the last node that
successfully processed a reservation request (see Section 4.6.1.2).
<B>: 1 bit. When set to "1", it indicates a bidirectional
reservation.
<Time Lag>: It represents the ratio between the "T_Lag" parameter,
which is the time difference between the departure time of the last
sent "PHR_Refresh_Update" control information container and the
departure time of the "PHR_Release_Request" control information
container, and the length of the refresh period, "T_period", see
Section 4.6.1.5.
<K>: 1 bit. When set to "1", it indicates that the
resources/bandwidth carried by a tearing RESERVE MUST NOT be
released, and the resources/bandwidth carried by a non-tearing
RESERVE MUST NOT be reserved/refreshed. For more details, see
Section 4.6.1.5.2.
<Max Admitted Hops>: 8 bits. The <Admitted Hops> value that has been
carried by the <PHR container> field used to identify the RMD
reservation-based node that admitted or processed a
"PHR_Resource_Request".
<SCH>: 3 bits. The <SCH> value that is used to specify which of the
6 RMD-QOSM scenarios (see Section 3.2.3) MUST be used within the RMD
domain. The operator of an RMD domain MUST preconfigure all the QNE
Edge nodes within one domain such that the <SCH> field included in
the "PHR container", will always use the same value, such that within
one RMD domain only one of the below described RMD-QOSM schemes can
be used at a time. All the QNE Interior nodes MUST interpret this
field before processing any other PHR container payload fields. The
currently defined <SCH> values are:
o 0: RMD-QOSM scheme MUST be "per-flow congestion notification
based on probing";
o 1: RMD-QOSM scheme MUST be "per-flow RMD NSIS measurement-
based admission control",
o 2: RMD-QOSM scheme MUST be "per-flow RMD reservation-based" in
combination with the "severe congestion handling by the
RMD-QOSM refresh" procedure;
o 3 : RMD-QOSM scheme MUST be "per-flow RMD reservation-based" in
combination with the "severe congestion handling by
proportional data packet marking" procedure;
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o 4: RMD-QOSM scheme MUST be "per-aggregate RMD reservation-
based" in combination with the "severe congestion handling
by the RMD-QOSM refresh" procedure;
o 5: RMD-QOSM scheme MUST be "per-aggregate RMD reservation-
based" in combination with the "severe congestion handling
by proportional data packet marking" procedure;
o 6 - 7: reserved.
The default value of the <SCH> field MUST be set to the value equal
to 3.
4.1.3. PDR Container
This section describes the parameters of the PDR container, which are
used by the RMD-QOSM functionality available at the Edge nodes.
The bit format of the PDR container can be seen in Figure 7.
<PDR container> = <O> <S> <M>
<Max Admitted Hops> <B> <SCH> [<PDR Bandwidth>]
In Figure 7, note that <Max Admitted Hops> is represented as <Max Adm
Hops>.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|E|N|r| Parameter ID |r|r|r|r| 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|M| Max Adm Hops |B|O| SCH | EMPTY |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PDR Bandwidth(32-bit IEEE floating point.number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: PDR container
Parameter ID: 12-bit field identifying the type of <PDR container>
field.
"PDR_Reservation_Request" (Parameter ID = 20): generated by the
QNE(Ingress) node in order to initiate or update the QoS-NSLP per-
domain reservation state in the QNE(Egress) node.
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"PDR_Refresh_Request" (Parameter ID = 21): generated by the
QNE(Ingress) node and sent to the QNE(Egress) node to refresh, in
case needed, the QoS-NSLP per-domain reservation states located in
the QNE(Egress) node.
"PDR_Release_Request" (Parameter ID = 22): generated and sent by the
QNE(Ingress) node to the QNE(Egress) node to release the per-domain
reservation states explicitly.
"PDR_Reservation_Report" (Parameter ID = 23): generated and sent by
the QNE(Egress) node to the QNE(Ingress) node to report that a
"PHR_Resource_Request" and a "PDR_Reservation_Request" traffic
handling directive field have been received and that the request has
been admitted or rejected.
"PDR_Refresh_Report" (Parameter ID = 24) generated and sent by the
QNE(Egress) node in case needed, to the QNE(Ingress) node to report
that a "PHR_Refresh_Update" traffic handling directive field has been
received and has been processed.
"PDR_Release_Report" (Parameter ID = 25) generated and sent by the
QNE(Egress) node in case needed, to the QNE(Ingress) node to report
that a "PHR_Release_Request" and a "PDR_Release_Request" traffic
handling directive field have been received and have been processed.
"PDR_Congestion_Report" (Parameter ID = 26): generated and sent by
the QNE(Egress) node to the QNE(Ingress) node and used for congestion
notification.
<S> (PDR Severe Congestion): 1 bit. Specifies if a severe congestion
situation occurred. It can also carry the <S> parameter of the
<PHR_Resource_Request> or <PHR_Refresh_Update> fields.
<O> (Overload): 1 bit. This field is used during the severe
congestion handling scheme that is using the RMD-QOSM refresh
procedure. This bit is set when an overload on a QNE Interior node
is detected and when this field is carried by the
"PDR_Congestion_Report" container. <O> SHOULD be set to "1" if the
<S> bit is set. For more details, see Section 4.6.1.6.1.
<M> (PDR Marked): 1 bit. Carries the <M> value of the
"PHR_Resource_Request" or "PHR_Refresh_Update" traffic handling
directive field.
<B>: 1 bit. Indicates bidirectional reservation.
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<Max Admitted Hops>: 8 bits. The <Admitted Hops> value that has been
carried by the <PHR container> field used to identify the RMD
reservation-based node that admitted or processed a
"PHR_Resource_Request".
<PDR Bandwidth>: 32 bits. This field specifies the bandwidth that
either applies when the <B> flag is set to "1" and when this
parameter is carried by a RESPONSE message or when a severe
congestion occurs and the QNE Edges maintain an aggregated intra-
domain QoS-NSLP operational state and it is carried by a NOTIFY
message. In the situation that the <B> flag is set to "1", this
parameter specifies the requested bandwidth that has to be reserved
by a node in the reverse direction and when the intra-domain
signaling procedures require a bidirectional reservation procedure.
In the severe congestion situation, this parameter specifies the
bandwidth that has to be released.
<SCH>: 3 bits. The <SCH> value that is used to specify which of the
6 RMD scenarios (see Section 3.2.3) MUST be used within the RMD
domain. The operator of an RMD domain MUST preconfigure all the QNE
Edge nodes within one domain such that the <SCH> field included in
the "PDR container", will always use the same value, such that within
one RMD domain only one of the below described RMD-QOSM schemes can
be used at a time. All the QNE Interior nodes MUST interpret this
field before processing any other <PDR container> payload fields.
The currently defined <SCH> values are:
o 0: RMD-QOSM scheme MUST be "per-flow congestion notification
based on probing";
o 1: RMD-QOSM scheme MUST be "per-flow RMD NSIS measurement-
based admission control";
o 2: RMD-QOSM scheme MUST be "per-flow RMD reservation-based" in
combination with the "severe congestion handling by the
RMD-QOSM refresh" procedure;
o 3 : RMD-QOSM scheme MUST be "per-flow RMD reservation-based" in
combination with the "severe congestion handling by
proportional data packet marking" procedure;
o 4: RMD-QOSM scheme MUST be "per-aggregate RMD reservation-
based" in combination with the "severe congestion handling
by the RMD-QOSM refresh" procedure;
o 5: RMD-QOSM scheme MUST be "per-aggregate RMD reservation-
based" in combination with the "severe congestion handling
by proportional data packet marking" procedure;
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o 6 - 7: reserved.
The default value of the <SCH> field MUST be set to the value equal
to 3.
4.2. Message Format
The format of the messages used by the RMD-QOSM complies with the
QoS-NSLP and QSPEC template specifications. The QSPEC used by RMD-
QOSM is denoted in this document as RMD-QSPEC and is described in
Section 4.1.
4.3. RMD Node State Management
The QoS-NSLP state creation and management is specified in [RFC5974].
This section describes the state creation and management functions of
the Resource Management Function (RMF) in the RMD nodes.
4.3.1. Aggregated Operational and Reservation States at the QNE Edges
The QNE Edges maintain both the intra-domain QoS-NSLP operational and
reservation states, while the QNE Interior nodes maintain only
reservation states. The structure of the intra-domain QoS-NSLP
operational state used by the QNE Edges is specified in [RFC5974].
In this case, the intra-domain sessions supported by the Edges are
per-aggregate sessions that have a one-to-many relationship to the
per-flow end-to-end states supported by the same Edge.
Note that the method of selecting the end-to-end sessions that form
an aggregate is not specified in this document. An example of how
this can be accomplished is by monitoring the GIST routing states
used by the end-to-end sessions and grouping the ones that use the
same <PHB Class>, QNE Ingress and QNE Egress addresses, and the value
of the priority level. Note that this priority level should be
deduced from the priority parameters carried by the initial QSPEC
object.
The operational state of this aggregated intra-domain session MUST
contain a list with BOUND-SESSION-IDs.
The structure of the list depends on whether a unidirectional
reservation or a bidirectional reservation is supported.
When the operational state (at QNE Ingress and QNE Egress) supports
unidirectional reservations, then this state MUST contain a list with
BOUND-SESSION-IDs maintaining the <SESSION-ID> values of its bound
end-to-end sessions. The Binding_Code associated with this BOUND-
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SESSION-ID is set to code (Aggregated sessions). Thus, the
operational state maintains a list of BOUND-SESSION-ID entries. Each
entry is created when an end-to-end session joins the aggregated
intra-domain session and is removed when an end-to-end session leaves
the aggregate.
It is important to emphasize that, in this case, the operational
state (at QNE Ingress and QNE Egress) that is maintained by each end-
to-end session bound to the aggregated intra-domain session MUST
contain in the BOUND-SESSION-ID, the <SESSION-ID> value of the bound
tunneled intra-domain (aggregate) session. The Binding_Code
associated with this BOUND-SESSION-ID is set to code (Aggregated
sessions).
When the operational state (at QNE Ingress and QNE Egress) supports
bidirectional reservations, the operational state MUST contain a list
of BOUND-SESSION-ID sets. Each set contains two BOUND-SESSION-IDs.
One of the BOUND-SESSION-IDs maintains the <SESSION-ID> value of one
of bound end-to-end session. The Binding_Code associated with this
BOUND-SESSION-ID is set to code (Aggregated sessions). Another
BOUND-SESSION-ID, within the same set entry, maintains the SESSION-ID
of the bidirectional bound end-to-end session. The Binding_Code
associated with this BOUND-SESSION-ID is set to code (Bidirectional
sessions).
Note that, in each set, a one-to-one relation exists between each
BOUND-SESSION-ID with Binding_Code set to (Aggregate sessions) and
each BOUND-SESSION-ID with Binding_Code set to (bidirectional
sessions). Each set is created when an end-to-end session joins the
aggregated operational state and is removed when an end-to-end
session leaves the aggregated operational state.
It is important to emphasize that, in this case, the operational
state (at QNE Ingress and QNE Egress) that is maintained by each end-
to-end session bound to the aggregated intra-domain session it MUST
contain two types of BOUND-SESSION-IDs. One is the BOUND-SESSION-ID
that MUST contain the <SESSION-ID> value of the bound tunneled
aggregated intra-domain session that is using the Binding_Code set to
(Aggregated sessions). The other BOUND-SESSION-ID maintains the
SESSION-ID of the bound bidirectional end-to-end session. The
Binding_Code associated with this BOUND-SESSION-ID is set to code
(Bidirectional sessions).
When the QNE Edges use aggregated QoS-NSLP reservation states, then
the <PHB Class> value and the size of the aggregated reservation,
e.g., reserved bandwidth, have to be maintained. Note that this type
of aggregation is an edge-to-edge aggregation and is similar to the
aggregation type specified in [RFC3175].
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The size of the aggregated reservations needs to be greater or equal
to the sum of bandwidth of the inter-domain (end-to-end)
reservations/sessions it aggregates (e.g., see Section 1.4.4 of
[RFC3175]).
A policy can be used to maintain the amount of REQUIRED bandwidth on
a given aggregated reservation by taking into account the sum of the
underlying inter-domain (end-to-end) reservations, while endeavoring
to change reservation less frequently. This MAY require a trend
analysis. If there is a significant probability that in the next
interval of time the current aggregated reservation is exhausted, the
Ingress router MUST predict the necessary bandwidth and request it.
If the Ingress router has a significant amount of bandwidth reserved,
but has very little probability of using it, the policy MAY predict
the amount of bandwidth REQUIRED and release the excess. To increase
or decrease the aggregate, the RMD modification procedures SHOULD be
used (see Section 4.6.1.4).
The QNE Interior nodes are reduced-state nodes, i.e., they do not
store NTLP/GIST states, but they do store per PHB-aggregated QoS-NSLP
reservation states. These reservation states are maintained and
refreshed in the same way as described in Section 4.3.3.
4.3.2. Measurement-Based Method
The QNE Edges maintain per-flow intra-domain QoS-NSLP operational and
reservation states that contain similar data structures as those
described in Section 4.3.1. The main difference is associated with
the different types of the used Message-Routing-Information (MRI) and
the bound end-to-end sessions. The structure of the maintained
BOUND-SESSION-IDs depends on whether a unidirectional reservation or
a bidirectional reservation is supported.
When unidirectional reservations are supported, the operational state
associated with this per-flow intra-domain session MUST contain in
the BOUND-SESSION-ID the <SESSION-ID> value of its bound end-to-end
session. The Binding_Code associated with this BOUND-SESSION-ID is
set to code (Tunneled and end-to-end sessions).
When bidirectional reservations are supported, the operational state
(at QNE Ingress and QNE Egress) MUST contain two types of BOUND-
SESSION-IDs. One is the BOUND-SESSION-ID that maintains the
<SESSION-ID> value of the bound tunneled per-flow intra-domain
session. The Binding_Code associated with this BOUND-SESSION-ID is
set to code (Tunneled and end-to-end sessions).
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The other BOUND-SESSION-ID maintains the SESSION-ID of the bound
bidirectional end-to-end session. The Binding_Code associated with
this BOUND-SESSION-ID is set to code (Bidirectional sessions).
Furthermore, the QoS-NSLP reservation state maintains the <PHB Class>
value, the value of the bandwidth requested by the end-to-end session
bound to the intra-domain session, and the value of the priority
level.
The measurement-based method can be classified in two schemes:
* Congestion notification based on probing:
In this scheme, the Interior nodes are Diffserv-aware but not NSIS-
aware nodes. Each Interior node counts the bandwidth that is used by
each PHB traffic class. This counter value is stored in an RMD_QOSM
state. For each PHB traffic class, a predefined congestion
notification threshold is set. The predefined congestion
notification threshold is set according to an engineered bandwidth
limitation based, e.g., on a Service Level Agreement or a capacity
limitation of specific links. The threshold is usually less than the
capacity limit, i.e., admission threshold, in order to avoid
congestion due to the error of estimating the actual traffic load.
The value of this threshold SHOULD be stored in another RMD_QOSM
state.
In this scenario, an end-to-end NSIS message is used as a probe
packet. In this case, the <DSCP> field of the GIST message is re-
marked when the predefined congestion notification threshold is
exceeded in an Interior node. It is required that the re-marking
happens to all packets that belong to the congested PHB traffic class
so that the probe can't pass the congested router without being re-
marked. In this way, it is ensured that the end-to-end NSIS message
passed through the node that is congested. This feature is very
useful when flow-based ECMP (Equal Cost Multiple Path) routing is
used to detect only flows that are passing through the congested
node.
* NSIS measurement-based admission control:
The measurement-based admission control is implemented in NSIS-aware
stateless routers. Thus, the main difference between this type of
the measurement-based admission control and the congestion
notification-based admission control is the fact that the Interior
nodes are NSIS-aware nodes. In particular, the QNE Interior nodes
operating in NSIS measurement-based mode are QoS-NSLP stateless
nodes, i.e., they do not support any QoS-NSLP or NTLP/GIST states.
These measurement-based nodes store two RMD-QOSM states per PHR
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group. These states reflect the traffic conditions at the node and
are not affected by QoS-NSLP signaling. One state stores the
measured user traffic load associated with the PHR group and another
state stores the maximum traffic load threshold that can be admitted
per PHR group. When a measurement-based node receives a intra-domain
RESERVE message, it compares the requested resources to the available
resources (maximum allowed minus current load) for the requested PHR
group. If there are insufficient resources, it sets the <M> bit in
the RMD-QSPEC. No change to the RMD-QSPEC is made when there are
sufficient resources.
4.3.3. Reservation-Based Method
The QNE Edges maintain intra-domain QoS-NSLP operational and
reservation states that contain similar data structures as described
in Section 4.3.1.
In this case, the intra-domain sessions supported by the Edges are
per-flow sessions that have a one-to-one relationship to the per-flow
end-to-end states supported by the same Edge.
The QNE Interior nodes operating in reservation-based mode are QoS-
NSLP reduced-state nodes, i.e., they do not store NTLP/GIST states
but they do store per PHB-aggregated QoS-NSLP states.
The reservation-based PHR installs and maintains one reservation
state per PHB, in all the nodes located in the communication path.
This state is identified by the <PHB Class> value and it maintains
the number of currently reserved resource units (or bandwidth).
Thus, the QNE Ingress node signals only the resource units requested
by each flow. These resource units, if admitted, are added to the
currently reserved resources per PHB.
For each PHB, a threshold is maintained that specifies the maximum
number of resource units that can be reserved. This threshold could,
for example, be statically configured.
An example of how the admission control and its maintenance process
occurs in the Interior nodes is described in Section 3 of [CsTa05].
The simplified concept that is used by the per-traffic class
admission control process in the Interior nodes, is based on the
following equation:
last + p <= T,
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where p is the requested bandwidth rate, T is the admission
threshold, which reflects the maximum traffic volume that can be
admitted in the traffic class, and last is a counter that records the
aggregated sum of the signaled bandwidth rates of previous admitted
flows.
The PHB group reservation states maintained in the Interior nodes are
soft states, which are refreshed by sending periodic refresh intra-
domain RESERVE messages, which are initiated by the Ingress QNEs. If
a refresh message corresponding to a number of reserved resource
units (i.e., bandwidth) is not received, the aggregated reservation
state is decreased in the next refresh period by the corresponding
amount of resources that were not refreshed. The refresh period can
be refined using a sliding window algorithm described in [RMD3].
The reserved resources for a particular flow can also be explicitly
released from a PHB reservation state by means of a intra-domain
RESERVE release/tear message, which is generated by the Ingress QNEs.
The use of explicit release enables the instantaneous release of the
resources regardless of the length of the refresh period. This
allows a longer refresh period, which also reduces the number of
periodic refresh messages.
Note that both in the case of measurement- and (per-flow and
aggregated) RMD reservation-based methods, the way in which the
maximum bandwidth thresholds are maintained is out of the
specification of this document. However, when admission priorities
are supported, the Maximum Allocation [RFC4125] or the Russian Dolls
[RFC4127] bandwidth allocation models MAY be used. In this case,
three types of priority traffic classes within the same PHB, e.g.,
Expedited Forwarding, can be differentiated. These three different
priority traffic classes, which are associated with the same PHB, are
denoted in this document as PHB_low_priority, PHB_normal_priority,
and PHB_high_priority, and are identified by the <PHB Class> value
and the priority value, which is carried in the <Admission Priority>
RMD-QSPEC parameter.
4.4. Transport of RMD-QOSM Messages
As mentioned in Section 1, the RMD-QOSM aims to support a number of
additional requirements, e.g., Minimal impact on Interior node
performance. Therefore, RMD-QOSM is designed to be very lightweight
signaling with regard to the number of signaling message round trips
and the amount of state established at involved signaling nodes with
and without reduced state on QNEs. The actions allowed by a QNE
Interior node are minimal (i.e., only those specified by the RMD-
QOSM).
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For example, only the QNE Ingress and the QNE Egress nodes are
allowed to initiate certain signaling messages. QNE Interior nodes
are, for example, allowed to modify certain signaling message
payloads. Moreover, RMD signaling is targeted towards intra-domain
signaling only. Therefore, RMD-QOSM relies on the security and
reliability support that is provided by the bound end-to-end session,
which is running between the boundaries of the RMD domain (i.e., the
RMD-QOSM QNE Edges), and the security provided by the D-mode. This
implies the use of the Datagram Mode.
Therefore, the intra-domain messages used by the RMD-QOSM are
intended to operate in the NTLP/GIST Datagram mode (see [RFC5971]).
The NSLP functionality available in all RMD-QOSM-aware QoS-NSLP nodes
requires the intra-domain GIST, via the QoS-NSLP RMF API see
[RFC5974], to:
* operate in unreliable mode. This can be satisfied by passing this
requirement from the QoS-NSLP layer to the GIST layer via the API
Transfer-Attributes.
* not create a message association state. This requirement can be
satisfied by a local policy, e.g., the QNE is configured to not
create a message association state.
* not create any NTLP routing state by the Interior nodes. This can
be satisfied by passing this requirement from the QoS-NSLP layer to
the GIST layer via the API. However, between the QNE Egress and
QNE Ingress routing states SHOULD be created that are associated
with intra-domain sessions and that can be used for the
communication of GIST Data messages sent by a QNE Egress directly
to a QNE Ingress. This type of routing state associated with an
intra-domain session can be generated and used in the following
way:
* When the QNE Ingress has to send an initial intra-domain RESERVE
message, the QoS-NSLP sends this message by including, in the GIST
API SendMessage primitive, the Unreliable and No security
attributes. In order to optimize this procedure, the RMD domain
MUST be engineered in such a way that GIST will piggyback this NSLP
message on a GIST Query message. Furthermore, GIST sets the C-flag
(C=1), see [RFC5971] and uses the Q-mode. The GIST functionality
in each QNE Interior node will receive the GIST Query message and
by using the RecvMessage GIST API primitive it will pass the intra-
domain RESERVE message to the QoS-NSLP functionality. At the same
time, the GIST functionality uses the Routing-State-Check boolean
to find out if the QoS-NSLP needs to create a routing state. The
QoS-NSLP sets this boolean to inform GIST to not create a routing
state and to forward the GIST Query further downstream with the
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modified QoS-NSLP payload, which will include the modified intra-
domain RESERVE message. The intra-domain RESERVE is sent in the
same way up to the QNE Egress. The QNE Egress needs to create a
routing state.
Therefore, at the same moment that the GIST functionality passes
the intra-domain RESERVE message, via the GIST RecvMessage
primitive, to the QoS-NSLP, the QoS-NSLP sets the Routing-State-
Check boolean such that a routing state is created. The GIST
creates the routing state using normal GIST procedures. After this
phase, the QNE Ingress and QNE Egress have, for the particular
session, routing states that can route traffic directly from QNE
Ingress to QNE Egress and from QNE Egress to QNE Ingress. The
routing state at the QNE Egress can be used by the QoS-NSLP and
GIST to send an intra-domain RESPONSE or intra-domain NOTIFY
directly to the QNE Ingress using GIST Data messages. Note that
this routing state is refreshed using normal GIST procedures. Note
that in the above description, it is considered that the QNE
Ingress can piggyback the initial RESERVE (NSLP) message on the
GIST Query message. If the piggybacking of this NSLP (initial
RESERVE) message would not be possible on the GIST Query message,
then the GIST Query message sent by the QNE Ingress node would not
contain any NSLP data. This GIST Query message would only be
processed by the QNE Egress to generate a routing state.
After the QNE Ingress is informed that the routing state at the QNE
Egress is initiated, it would have to send the initial RESERVE
message using similar procedures as for the situation that it would
send an intra-domain RESERVE message that is not an initial
RESERVE, see next bullet. This procedure is not efficient and
therefore it is RECOMMENDED that the RMD domain MUST be engineered
in such a way that the GIST protocol layer, which is processed on a
QNE Ingress, will piggyback an initial RESERVE (NSLP) message on a
GIST Query message that uses the Q-mode.
* When the QNE Ingress needs to send an intra-domain RESERVE message
that is not an initial RESERVE, then the QoS-NSLP sends this
message by including in the GIST API SendMessage primitive such
attributes that the use of the Datagram Mode is implied, e.g., the
Unreliable attribute. Furthermore, the Local policy attribute is
set such that GIST sends the intra-domain RESERVE message in a
Q-mode even if there is a routing state at the QNE Ingress. In
this way, the GIST functionality uses its local policy to send the
intra-domain RESERVE message by piggybacking it on a GIST Data
message and sending it in Q-mode even if there is a routing state
for this session. The intra-domain RESERVE message is piggybacked
on the GIST Data message that is forwarded and processed by the QNE
Interior nodes up to the QNE Egress.
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The transport of the original (end-to-end) RESERVE message is
accomplished in the following way:
At the QNE Ingress, the original (end-to-end) RESERVE message is
forwarded but ignored by the stateless or reduced-state nodes, see
Figure 3.
The intermediate (Interior) nodes are bypassed using multiple levels
of NSLPID values (see [RFC5974]). This is accomplished by marking
the end-to-end RESERVE message, i.e., modifying the QoS-NSLP default
NSLPID value to another NSLPID predefined value.
The marking MUST be accomplished by the Ingress by modifying the
QoS_NSLP default NSLPID value to a NSLPID predefined value. In this
way, the Egress MUST stop this marking process by reassigning the
QoS-NSLP default NSLPID value to the original (end-to-end) RESERVE
message. Note that the assignment of these NSLPID values is a QoS-
NSLP issue, which SHOULD be accomplished via IANA [RFC5974].
4.5. Edge Discovery and Message Addressing
Mainly, the Egress node discovery can be performed by using either
the GIST discovery mechanism [RFC5971], manual configuration, or any
other discovery technique. The addressing of signaling messages
depends on which GIST transport mode is used. The RMD-QOSM/QoS-NSLP
signaling messages that are processed only by the Edge nodes use the
peer-peer addressing of the GIST Connection (C) mode.
RMD-QOSM/QoS-NSLP signaling messages that are processed by all nodes
of the Diffserv domain, i.e., Edges and Interior nodes, use the end-
to-end addressing of the GIST Datagram (D) mode. Note that the RMD-
QOSM cannot directly specify that the GIST Connection or the GIST
Datagram mode SHOULD be used. This can only be specified by using,
via the QoS-NSLP-RMF API, the GIST API Transfer-Attributes, such as
Reliable or Unreliable, high or low level of security, and by the use
of local policies. RMD QoS signaling messages that are addressed to
the data path end nodes are intercepted by the Egress nodes. In
particular, at the ingress and for downstream intra-domain messages,
the RMD-QOSM instructs the GIST functionality, via the GIST API to do
the following:
* use unreliable and low level security Transfer-Attributes,
* do not create a GIST routing state, and
* use the D-mode MRI.
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The intra-domain RESERVE messages can then be transported by using
the Query D-mode; see Section 4.4.
At the QNE Egress, and for upstream intra-domain messages, the RMD-
QOSM instructs the GIST functionality, via the GIST API, to use among
others:
* unreliable and low level security Transfer-Attributes
* the routing state associated with the intra-domain session to send
an upstream intra-domain message directly to the QNE Ingress; see
Section 4.4.
4.6. Operation and Sequence of Events
4.6.1. Basic Unidirectional Operation
This section describes the basic unidirectional operation and
sequence of events/triggers of the RMD-QOSM. The following basic
operation cases are distinguished:
* Successful reservation (Section 4.6.1.1),
* Unsuccessful reservation (Section 4.6.1.2),
* RMD refresh reservation (Section 4.6.1.3),
* RMD modification of aggregated reservation (Section 4.6.1.4),
* RMD release procedure (Section 4.6.1.5.),
* Severe congestion handling (Section 4.6.1.6.),
* Admission control using congestion notification based on probing
(Section 4.6.1.7.).
The QNEs at the Edges of the RMD domain support the RMD QoS Model and
end-to-end QoS Models, which process the RESERVE message differently.
Note that the term end-to-end QoS Model applies to any QoS Model that
is initiated and terminated outside the RMD-QOSM-aware domain.
However, there might be situations where a QoS Model is initiated
and/or terminated by the QNE Edges and is considered to be an end-to-
end QoS Model. This can occur when the QNE Edges can also operate as
either QNI or as QNR and at the same time they can operate as either
sender or receiver of the data path.
It is important to emphasize that the content of this section is used
for the specification of the following RMD-QOSM/QoS-NSLP signaling
schemes, when basic unidirectional operation is assumed:
* "per-flow congestion notification based on probing";
* "per-flow RMD NSIS measurement-based admission control";
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* "per-flow RMD reservation-based" in combination with the "severe
congestion handling by the RMD-QOSM refresh" procedure;
* "per-flow RMD reservation-based" in combination with the "severe
congestion handling by proportional data packet marking" procedure;
* "per-aggregate RMD reservation-based" in combination with the
"severe congestion handling by the RMD-QOSM refresh" procedure;
* "per-aggregate RMD reservation-based" in combination with the
"severe congestion handling by proportional data packet marking"
procedure.
For more details, please see Section 3.2.3.
In particular, the functionality described in Sections 4.6.1.1,
4.6.1.2, 4.6.1.3, 4.6.1.5, 4.6.1.4, and 4.6.1.6 applies to the RMD
reservation-based and to the NSIS measurement-based admission control
methods. The described functionality in Section 4.6.1.7 applies to
the admission control procedure that uses the congestion notification
based on probing. The QNE Edge nodes maintain either per-flow QoS-
NSLP operational and reservation states or aggregated QoS-NSLP
operational and reservation states.
When the QNE Edges maintain aggregated QoS-NSLP operational and
reservation states, the RMD-QOSM functionality MAY accomplish an RMD
modification procedure (see Section 4.6.1.4), instead of the
reservation initiation procedure that is described in this
subsection. Note that it is RECOMMENDED that the QNE implementations
of RMD-QOSM process the QoS-NSLP signaling messages with a higher
priority than data packets. This can be accomplished as described in
Section 3.3.4 of [RFC5974] and it can be requested via the QoS-NSLP-
RMF API described in [RFC5974]. The signaling scenarios described in
this section are accomplished using the QoS-NSLP processing rules
defined in [RFC5974], in combination with the RMF triggers sent via
the QoS-NSLP-RMF API described in [RFC5974].
According to Section 3.2.3, it is specified that only the "per-flow
RMD reservation-based" in combination with the "severe congestion
handling by proportional data packet marking" scheme MUST be
implemented within one RMD domain. However, all RMD QNEs supporting
this specification MUST support the combination the "per-flow RMD
reservation-based" in combination with the "severe congestion
handling by proportional data packet marking" scheme. If the RMD
QNEs support more RMD-QOSM schemes, then the operator of that RMD
domain MUST preconfigure all the QNE Edge nodes within one domain
such that the <SCH> field included in the "PHR container" (Section
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4.1.2) and the "PDR Container" (Section 4.1.3) will always use the
same value, such that within one RMD domain only one of the below
described RMD-QOSM schemes is used at a time.
All QNE nodes located within the RMD domain MUST read and interpret
the <SCH> field included in the "PHR container" before processing all
the other "PHR container" payload fields. Moreover, all QNE Edge
nodes located at the boarder of the RMD domain, MUST read and
interpret the <SCH> field included in the "PDR container" before
processing all the other <PDR container> payload fields.
4.6.1.1. Successful Reservation
This section describes the operation of the RMD-QOSM where a
reservation is successfully accomplished.
The QNI generates the initial RESERVE message, and it is forwarded by
the NTLP as usual [RFC5971].
4.6.1.1.1. Operation in Ingress Node
When an end-to-end reservation request (RESERVE) arrives at the
Ingress node (QNE) (see Figure 8), it is processed based on the end-
to-end QoS Model. Subsequently, the combination of <TMOD-1>, <PHB
Class>, and <Admission Priority> is derived from the <QoS Desired>
object of the initial QSPEC.
The QNE Ingress MUST maintain information about the smallest MTU that
is supported on the links within the RMD domain.
The <Maximum Packet Size-1 (MPS)> value included in the end-to-end
QoS Model <TMOD-1> parameter is compared with the smallest MTU value
that is supported by the links within the RMD domain. If the
"Maximum Packet Size-1 (MPS)" is larger than this smallest MTU value
within the RMD domain, then the end-to-end reservation request is
rejected (see Section 4.6.1.1.2). Otherwise, the admission process
continues.
The <TMOD-1> parameter contained in the original initiator QSPEC is
mapped into the equivalent RMD-Qspec <TMOD-1> parameter representing
only the peak bandwidth in the local RMD-QSPEC. This can be
accomplished by setting the RMD-QSPEC <TMOD-1> fields as follows:
token rate (r) = peak traffic rate (p), the bucket depth (b) = large,
and the minimum policed unit (m) = large.
Note that the bucket size, (b), is measured in bytes. Values of this
parameter may range from 1 byte to 250 gigabytes; see [RFC2215].
Thus, the maximum value that (b) could be is in the order of 250
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gigabytes. The minimum policed unit, [m], is an integer measured in
bytes and must be less than or equal to the Maximum Packet Size
(MPS). Thus, the maximum value that (m) can be is (MPS). [Part94]
and [TaCh99] describe a method of calculating the values of some
Token Bucket parameters, e.g., calculation of large values of (m) and
(b), when the token rate (r), peak rate (p), and MPS are known.
The <Peak Data Rate-1 (p)> value of the end-to-end QoS Model <TMOD-1>
parameter is copied into the <Peak Data Rate-1 (p)> value of the
<Peak Data Rate-1 (p)> value of the local RMD-Qspec <TMOD-1>.
The MPS value of the end-to-end QoS Model <TMOD-1> parameter is
copied into the MPS value of the local RMD-Qspec <TMOD-1>.
If the initial QSPEC does not contain the <PHB Class> parameter, then
the selection of the <PHB Class> that is carried by the intra-domain
RMD-QSPEC is defined by a local policy similar to the procedures
discussed in [RFC2998] and [RFC3175].
For example, in the situation that the initial QSPEC is used by the
IntServ Controlled Load QOSM, then the Expedited Forwarding (EF) PHB
is appropriate to set the <PHB Class> parameter carried by the intra-
domain RMD-QSPEC (see [RFC3175]).
If the initial QSPEC does not carry the <Admission Priority>
parameter, then the <Admission Priority> parameter in the RMD-QSPEC
will not be populated. If the initial QSPEC does not carry the
<Admission Priority> parameter, but it carries other priority
parameters, then it is considered that Edges, as being stateful
nodes, are able to control the priority of the sessions that are
entering or leaving the RMD domain in accordance with the priority
parameters.
Note that the RMF reservation states (see Section 4.3) in the QNE
Edges store the value of the <Admission Priority> parameter that is
used within the RMD domain in case of preemption and severe
congestion situations (see Section 4.6.1.6).
If the RMD domain supports preemption during the admission control
process, then the QNE Ingress node can support the building blocks
specified in [RFC5974] and during the admission control process use
the example preemption handling algorithm described in Appendix A.7.
Note that in the above described case, the QNE Egress uses, if
available, the tunneled initial priority parameters, which can be
interpreted by the QNE Egress.
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If the initial QSPEC carries the <Excess Treatment> parameter, then
the QNE Ingress and QNE Egress nodes MUST control the excess traffic
that is entering or leaving the RMD domain in accordance with the
<Excess Treatment> parameter. Note that the RMD-QSPEC does not carry
the <Excess Treatment> parameter.
If the requested <TMOD-1> parameter carried by the initial QSPEC,
cannot be satisfied, then an end-to-end RESPONSE message has to be
generated. However, in order to decide whether the end-to-end
reservation request was locally (at the QNE Ingress) satisfied, a
local (at the QNE_Ingress) RMD-QOSM admission control procedure also
has to be performed. In other words, the RMD-QOSM functionality has
to verify whether the value included in the <Peak Data Rate-1 (p)>
field of RMD-QOSM <TMOD-1> can be reserved and stored in the RMD-QOSM
reservation states (see Sections 4.6.1.1.2 and 4.3).
An initial QSPEC object MUST be included in the end-to-end RESPONSE
message. The parameters included in the QSPEC <QoS Reserved> object
are copied from the original <QoS Desired> values.
The <E> flag associated with the QSPEC <QoS Reserved> object and the
<E> flag associated with the local RMD-QSPEC <TMOD-1> parameter are
set. In addition, the <INFO-SPEC> object is included in the end-to-
end RESPONSE message. The error code used by this <INFO-SPEC> is:
Error severity class: Transient Failure Error code value: Reservation
failure
Furthermore, all of the other RESPONSE parameters are set according
to the end-to-end QoS Model or according to [RFC5974] and [RFC5975].
If the request was satisfied locally (see Section 4.3), the Ingress
QNE node generates two RESERVE messages: one intra-domain and one
end-to-end RESERVE message. Note however, that when the aggregated
QoS-NSLP operational and reservation states are used by the QNE
Ingress, then the generation of the intra-domain RESERVE message
depends on the availability of the aggregated QoS-NSLP operational
state. If this aggregated QoS-NSLP operational state is available,
then the RMD modification of aggregated reservations described in
Section 4.6.1.4 is used.
It is important to note that when the "per-flow RMD reservation-
based" scenario is used within the RMD domain, the retransmission
within the RMD domain SHOULD be disallowed. The reason for this is
related to the fact that the QNI Interior nodes are not able to
differentiate between a retransmitted RESERVE message associated with
a certain session and an initial RESERVE message belonging to another
session. However, the QNE Ingress have to report a failure situation
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upstream. When the QNE Ingress transmits the (intra-domain or end-
to-end) RESERVE with the <RII> object set, it waits for a RESPONSE
from the QNE Egress for a QOSNSLP_REQUEST_RETRY period.
If the QNE Ingress transmitted an intra-domain or end-to-end RESERVE
message with the <RII> object set and it fails to receive the
associated intra-domain or end-to-end RESPONSE, respectively, after
the QOSNSLP_REQUEST_RETRY period expires, it considers that the
reservation failed. In this case, the QNE Ingress SHOULD generate an
end-to-end RESPONSE message that will include, among others, an
<INFO-SPEC> object. The error code used by this <INFO-SPEC> object
is:
Error severity class: Transient Failure
Error code value: Reservation failure
Furthermore, all of the other RESPONSE parameters are set according
to the end-to-end QoS Model or according to [RFC5974] and [RFC5975].
Note however, that if the retransmission within the RMD domain is not
disallowed, then the procedure described in Appendix A.8 SHOULD be
used on QNE Interior nodes; see also [Chan07]. In this case, the
stateful QNE Ingress uses the retransmission procedure described in
[RFC5974].
If a rerouting takes place, then the stateful QNE Ingress is
following the procedures specified in [RFC5974].
At this point, the intra-domain and end-to-end operational states
MUST be initiated or modified according to the REQUIRED binding
procedures. The way of how the BOUND-SESSION-IDs are initiated and
maintained in the intra-domain and end-to-end QoS-NSLP operational
states is described in Sections 4.3.1 and 4.3.2.
These two messages are bound together in the following way. The end-
to-end RESERVE SHOULD contain, in the BOUND-SESSION-ID, the SESSION-
ID of its bound intra-domain session.
Furthermore, if the QNE Edge nodes maintain intra-domain per-flow
QoS-NSLP reservation states, then the value of Binding_Code MUST be
set to code "Tunnel and end-to-end sessions" (see Section 4.3.2).
In addition to this, the intra-domain and end-to-end RESERVE messages
are bound using the Message binding procedure described in [RFC5974].
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In particular the <MSG-ID> object is included in the intra-domain
RESERVE message and its bound <BOUND-MSG-ID> object is carried by the
end-to-end RESERVE message. Furthermore, the <Message_Binding_Type>
flag is SET (value is 1), such that the message dependency is
bidirectional.
If the QoS-NSLP Edges maintain aggregated intra-domain QoS-NSLP
operational states, then the value of Binding_Code MUST be set to
code "Aggregated sessions".
Furthermore, in this case, the retransmission within the RMD domain
is allowed and the procedures described in Appendix A.8 SHOULD be
used on QNE Interior nodes. This is necessary due to the fact that
when retransmissions are disallowed, then the associated with (micro)
flows belonging to the aggregate will loose their reservations. Note
that, in this case, the stateful QNE Ingress uses the retransmission
procedure described in [RFC5974].
The intra-domain RESERVE message is associated with the (local NTLP)
SESSION-ID mentioned above. The selection of the IP source and IP
destination address of this message depends on how the different
inter-domain (end-to-end) flows are aggregated by the QNE Ingress
node (see Section 4.3.1). As described in Section 4.3.1, the QNE
Edges maintain either per-flow, or aggregated QoS-NSLP reservation
states for the RMD QoS Model, which are identified by (local NTLP)
SESSION-IDs (see [RFC5971]). Note that this NTLP SESSION-ID is a
different one than the SESSION-ID associated with the end-to-end
RESERVE message.
If no QoS-NSLP aggregation procedure at the QNE Edges is supported,
then the IP source and IP destination address of this message MUST be
equal to the IP source and IP destination addresses of the data flow.
The intra-domain RESERVE message is sent using the NTLP datagram mode
(see Sections 4.4 and 4.5). Note that the GIST Datagram mode can be
selected using the unreliable GIST API Transfer-Attributes. In
addition, the intra-domain RESERVE (RMD-QSPEC) message MUST include a
PHR container (PHR_Resource_Request) and the RMD QOSM <QoS Desired>
object.
The end-to-end RESERVE message includes the initial QSPEC and it is
sent towards the Egress QNE.
Note that after completing the initial discovery phase, the GIST
Connection mode can be used between the QNE Ingress and QNE Egress.
Note that the GIST Connection mode can be selected using the reliable
GIST API Transfer-Attributes.
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The end-to-end RESERVE message is forwarded using the GIST forwarding
procedure to bypass the Interior stateless or reduced-state QNE
nodes; see Figure 8. The bypassing procedure is described in Section
4.4.
At the QNE Ingress, the end-to-end RESERVE message is marked, i.e.,
modifying the QoS-NSLP default NSLPID value to another NSLPID
predefined value that will be used by the GIST message carrying the
end-to-end RESPONSE message to bypass the QNE Interior nodes. Note
that the QNE Interior nodes (see [RFC5971]) are configured to handle
only certain NSLP-IDs (see [RFC5974]).
Furthermore, note that the initial discovery phase and the process of
sending the end-to-end RESERVE message towards the QNE Egress MAY be
done simultaneously. This can be accomplished only if the GIST
implementation is configured to perform that, e.g., via a local
policy. However, the selection of the discovery procedure cannot be
selected by the RMD-QOSM.
The (initial) intra-domain RESERVE message MUST be sent by the QNE
Ingress and it MUST contain the following values (see the QoS-NSLP-
RMF API described in [RFC5974]):
* the <RSN> object, whose value is generated and processed as
described in [RFC5974];
* the <SCOPING> flag MUST NOT be set, meaning that a default
scoping of the message is used. Therefore, the QNE Edges MUST
be configured as RMD boundary nodes and the QNE Interior nodes
MUST be configured as Interior (intermediary) nodes;
* the <RII> MUST be included in this message, see [RFC5974];
* the <REPLACE> flag MUST be set to FALSE = 0;
* The value of the <Message ID> value carried by the <MSG-ID> object
is set according to [RFC5974]. The value of the
<Message_Binding_Type> is set to "1".
* the value of the <REFRESH-PERIOD> object MUST be calculated and
set by the QNE Ingress node as described in Section 4.6.1.3;
* the value of the <PACKET-CLASSIFIER> object is associated with the
path-coupled routing Message Routing Message (MRM), since RMD-QOSM
is used with the path-coupled MRM. The flag that has to be set is
the <T> flag (traffic class) meaning that the packet
classification of packets is based on the <DSCP> value included in
the IP header of the packets. Note that the <DSCP> value used in
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the MRI can be derived by the value of <PHB Class> parameter,
which MUST be carried by the intra-domain RESERVE message. Note
that the QNE Ingress being a QNI for the intra-domain session it
can pass this value to GIST, via the GIST API.
* the PHR resource units MUST be included in the <Peak Data Rate-1
(p)> field of the local RMD-QSPEC <TMOD-1> parameter of the <QoS
Desired> object.
When the QNE Edges use per-flow intra-domain QoS-NSLP states, then
the <Peak Data Rate-1 (p)> value included in the initial QSPEC
<TMOD-1> parameter is copied into the <Peak Data Rate-1 (p)> value
of the local RMD-QSPEC <TMOD-1> parameter.
When the QNE Edges use aggregated intra-domain QoS-NSLP
operational states, then the <Peak Data Rate-1 (p)> value of the
local RMD-QSPEC <TMOD-1> parameter can be obtained by using the
bandwidth aggregation method described in Section 4.3.1;
* the value of the <PHB Class> parameter can be defined by using the
method of copying the <PHB Class> parameter carried by the initial
QSPEC into the <PHB Class> carried by the RMD-QSPEC, which is
described above in this subsection.
* the value of the <Parameter ID> field of the PHR container MUST be
set to "17", (i.e., PHR_Resource_Request).
* the value of the <Admitted Hops> parameter in the PHR container
MUST be set to "1". Note that during a successful reservation,
each time an RMD-QOSM-aware node processes the RMD-QSPEC, the
<Admitted Hops> parameter is increased by one.
* the value of the <Hop_U> parameter in the PHR container MUST be
set to "0".
* the value of the <Max Admitted Hops> is set to "0".
* If the initial QSPEC carried an <Admission Priority> parameter,
then this parameter SHOULD be copied into the RMD-QSPEC and
carried by the (initiating) intra-domain RESERVE.
Note that for the RMD-QOSM, a reservation established without an
<Admission Priority> parameter is equivalent to a reservation with
<Admission Priority> value of 1.
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Note that, in this case, each admission priority is associated
with a priority traffic class. The three priority traffic classes
(PHB_low_priority, PHB_normal_priority, and PHB_high_priority) MAY
be associated with the same PHB (see Section 4.3.3).
* In a single RMD domain case, the PDR container MAY not be included
in the message.
Note that the intra-domain RESERVE message does not carry the <BOUND-
SESSION-ID> object. The reason for this is that the end-to-end
RESERVE carries, in the <BOUND-SESSION-ID> object, the <SESSION-ID>
value of the intra-domain session.
When an end-to-end RESPONSE message is received by the QNE Ingress
node, which was sent by a QNE Egress node (see Section 4.6.1.1.3),
then it is processed according to [RFC5974] and end-to-end QoS Model
rules.
When an intra-domain RESPONSE message is received by the QNE Ingress
node, which was sent by a QNE Egress (see Section 4.6.1.1.3), it uses
the QoS-NSLP procedures to match it to the earlier sent intra-domain
RESERVE message. After this phase, the RMD-QSPEC has to be
identified and processed.
The RMD QOSM reservation has been successful if the <M> bit carried
by the "PDR Container" is equal to "0" (i.e., not set).
Furthermore, the <INFO-SPEC> object is processed as defined in the
QoS-NSLP specification. In the case of successful reservation, the
<INFO-SPEC> object MUST have the following values:
* Error severity class: Success
* Error code value: Reservation successful
If the end-to-end RESPONSE message has to be forwarded to a node
outside the RMD-QOSM-aware domain, then the values of the objects
contained in this message (i.e., <RII> <RSN>, <INFO-SPEC>, [<QSPEC>])
MUST be set by the QoS-NSLP protocol functions of the QNE. If an
end-to-end QUERY is received by the QNE Ingress, then the same
bypassing procedure has to be used as the one applied for an end-to-
end RESERVE message. In particular, it is forwarded using the GIST
forwarding procedure to bypass the Interior stateless or reduced-
state QNE nodes.
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4.6.1.1.2. Operation in the Interior Nodes
Each QNE Interior node MUST use the QoS-NSLP and RMD-QOSM parameters
of the intra-domain RESERVE (RMD-QSPEC) message as follows (see QoS-
NSLP-RMF API described in [RFC5974]):
* the values of the <RSN>, <RII>, <PACKET-CLASSIFIER>, <REFRESH-
PERIOD>, objects MUST NOT be changed.
The Interior node is informed by the <PACKET-CLASSIFIER> object
that the packet classification SHOULD be done on the <DSCP> value.
The flag that has to be set in this case is the <T> flag (traffic
class). The value of the <DSCP> value MUST be obtained via the
MRI parameters that the QoS-NSLP receives from GIST. A QNE
Interior MUST be able to associate the value carried by the RMD-
QSPEC <PHB Class> parameter and the <DSCP> value obtained via
GIST. This is REQUIRED, because there are situations in which the
<PHB Class> parameter is not carrying a <DSCP> value but a PHB ID
code, see Section 4.1.1.
* the flag <REPLACE> MUST be set to FALSE = 0;
* when the RMD reservation-based methods, described in Section 4.3.1
and 4.3.3, are used, the <Peak Data Rate-1 (p)> value of the local
RMD-QSPEC <TMOD-1> parameter is used by the QNE Interior node for
admission control. Furthermore, if the <Admission Priority>
parameter is carried by the RMD-QOSM <QoS Desired> object, then
this parameter is processed as described in the following bullets.
* in the case of the RMD reservation-based procedure, and if these
resources are admitted (see Sections 4.3.1 and 4.3.3), they are
added to the currently reserved resources. Furthermore, the value
of the <Admitted Hops> parameter in the PHR container has to be
increased by one.
* If the bandwidth allocated for the PHB_high_priority traffic is
fully utilized, and a high priority request arrives, other
policies on allocating bandwidth can be used, which are beyond the
scope of this document.
* If the RMD domain supports preemption during the admission control
process, then the QNE Interior node can support the building
blocks specified in the [RFC5974] and during the admission control
process use the preemption handling algorithm specified in
Appendix A.7.
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* in the case of the RMD measurement-based method (see Section
4.3.2), and if the requested into the <Peak Data Rate-1 (p)> value
of the local RMD-QSPEC <TMOD-1> parameter is admitted, using a
measurement-based admission control (MBAC) algorithm, then the
number of this resource will be used to update the MBAC algorithm
according to the operation described in Section 4.3.2.
4.6.1.1.3. Operation in the Egress Node
When the end-to-end RESERVE message is received by the egress node,
it is only forwarded further, towards QNR, if the processing of the
intra-domain RESERVE(RMD-QSPEC) message was successful at all nodes
in the RMD domain. In this case, the QNE Egress MUST stop the
marking process that was used to bypass the QNE Interior nodes by
reassigning the QoS-NSLP default NSLPID value to the end-to-end
RESERVE message (see Section 4.4). Furthermore, the carried <BOUND-
SESSION-ID> object associated with the intra-domain session MUST be
removed after processing. Note that the received end-to-end RESERVE
was tunneled within the RMD domain. Therefore, the tunneled initial
QSPEC carried by the end-to-end RESERVE message has to be
processed/set according to the [RFC5975] specification.
If a rerouting takes place, then the stateful QNE Egress is following
the procedures specified in [RFC5974].
At this point, the intra-domain and end-to-end operational states
MUST be initiated or modified according to the REQUIRED binding
procedures.
The way in which the BOUND-SESSION-IDs are initiated and maintained
in the intra-domain and end-to-end QoS-NSLP operational states is
described in Sections 4.3.1 and 4.3.2.
If the processing of the intra-domain RESERVE(RMD-QSPEC) was not
successful at all nodes in the RMD domain, then the inter-domain
(end-to-end) reservation is considered to have failed.
Furthermore, if the initial QSPEC object used an object combination
of type 1 or 2 where the <QoS Available> is populated, and the intra-
domain RESERVE(RMD-QSPEC) was not successful at all nodes in the RMD
domain MUST be considered that the <QoS Available> is not satisfied
and that the inter-domain (end-to-end) reservation is considered to
have failed.
Furthermore, note that when the QNE Egress uses per-flow intra-domain
QoS-NSLP operational states (see Sections 4.3.2 and 4.3.3), the QNE
Egress SHOULD support the message binding procedure described in
[RFC5974], which can be used to synchronize the arrival of the end-
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to-end RESERVE and the intra-domain RESERVE (RMD-QSPEC) messages, see
Section 5.7, and QoS-NSLP-RMF API described in [RFC5974]. Note that
the intra-domain RESERVE message carries the <MSG-ID> object and its
bound end-to-end RESERVE message carries the <BOUND-MSG-ID> object.
Both these objects carry the <Message_Binding_Type> flag set to the
value of "1". If these two messages do not arrive during the time
defined by the MsgIDWait timer, then the reservation is considered to
have failed. Note that the timer has to be preconfigured and it has
to have the same value in the RMD domain. In this case, an end-to-
end RESPONSE message, see QoS-NSLP-RMF API described in [RFC5974], is
sent towards the QNE Ingress with the following <INFO-SPEC> values:
Error class: Transient Failure
Error code: Mismatch synchronization between end-to-end RESERVE
and intra-domain RESERVE
When the intra-domain RESERVE (RMD-QSPEC) is received by the QNE
Egress node of the session associated with the intra-domain
RESERVE(RMD-QSPEC) (the PHB session) with the session included in its
<BOUND-SESSION-ID> object MUST be bound according to the
specification given in [RFC5974]. The SESSION-ID included in the
BOUND-SESSION-ID parameter stored in the intra-domain QoS-NSLP
operational state object is the SESSION-ID of the session associated
with the end-to-end RESERVE message(s). Note that if the QNE Edge
nodes maintain per-flow intra-domain QoS-NSLP operational states,
then the value of Binding_Code = (Tunnel and end-to-end sessions) is
used. If the QNE Edge nodes maintain per-aggregated QoS-NSLP intra-
domain reservation states, then the value of Binding_Code =
(Aggregated sessions), see Sections 4.3.1 and 4.3.2.
If the RMD domain supports preemption during the admission control
process, then the QNE Egress node can support the building blocks
specified in the [RFC5974] and during the admission control process
use the example preemption handling algorithm described in Appendix
A.7.
The end-to-end RESERVE message is generated/forwarded further
upstream according to the [RFC5974] and [RFC5975] specifications.
Furthermore, the <B> (BREAK) QoS-NSLP flag in the end-to-end RESERVE
message MUST NOT be set, see the QoS-NSLP-RMF API described in QoS-
NSLP.
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QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
RESERVE | | |
--->| | | RESERVE |
|------------------------------------------------------------>|
|RESERVE(RMD-QSPEC) | | |
|------------------->| | |
| |RESERVE(RMD-QSPEC) | |
| |------------------>| |
| | | RESERVE(RMD-QSPEC) |
| | |------------------->|
| |RESPONSE(RMD-QSPEC)| |
|<------------------------------------------------------------|
| | | RESERVE
| | | |-->
| | | RESPONSE
| | | |<--
| |RESPONSE | |
|<------------------------------------------------------------|
RESPONSE | | |
<---| | | |
Figure 8: Basic operation of successful reservation procedure
used by the RMD-QOSM
The QNE Egress MUST generate an intra-domain RESPONSE (RMD-Qspec)
message. The intra-domain RESPONSE (RMD-QSPEC) message MUST be sent
to the QNE Ingress node, i.e., the previous stateful hop by using the
procedures described in Sections 4.4 and 4.5.
The values of the RMD-QSPEC that are carried by the intra-domain
RESPONSE message MUST be used and/or set in the following way (see
the QoS-NSLP-RMF API described in [RFC5974]):
* the <RII> object carried by the intra-domain RESERVE message, see
Section 4.6.1.1.1, has to be copied and carried by the intra-
domain RESPONSE message.
* the value of the <Parameter ID> field of the PDR container MUST be
set to "23" (i.e., PDR_Reservation_Report);
* the value of the <M> field of the PDR container MUST be equal to
the value of the <M> parameter of the PHR container that was
carried by its associated intra-domain RESERVE(RMD-QSPEC) message.
This is REQUIRED since the value of the <M> parameter is used to
indicate the status if the RMD reservation request to the Ingress
Edge.
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If the binding between the intra-domain session and the end-to-end
session uses a Binding_Code that is (Aggregated sessions), and there
is no aggregated QoS-NSLP operational state associated with the
intra-domain session available, then the RMD modification of
aggregated reservation procedure described in Section 4.6.1.4 can be
used.
If the QNE Egress receives an end-to-end RESPONSE message, it is
processed and forwarded towards the QNE Ingress. In particular, the
non-default values of the objects contained in the end-to-end
RESPONSE message MUST be used and/or set by the QNE Egress as follows
(see the QoS-NSLP-RMF API described in [RFC5974]):
* the values of the <RII>, <RSN>, <INFO-SPEC>, [<QSPEC>] objects are
set according to [RFC5974] and/or [RFC5975]. The <INFO-SPEC>
object SHOULD be set by the QoS-NSLP functionality. In the case
of successful reservation, the <INFO-SPEC> object SHOULD have the
following values:
Error severity class: Success Error code value: Reservation
successful
* furthermore, an initial QSPEC object MUST be included in the end-
to-end RESPONSE message. The parameters included in the QSPEC
<QoS Reserved> object are copied from the original <QoS Desired>
values.
The end-to-end RESPONSE message is delivered as normal, i.e., is
addressed and sent to its upstream QoS-NSLP neighbor, i.e., the QNE
Ingress node.
Note that if a QNE Egress receives an end-to-end QUERY that was
bypassed through the RMD domain, it MUST stop the marking process
that was used to bypass the QNE Interior nodes. This can be done by
reassigning the QoS-NSLP default NSLPID value to the end-to-end QUERY
message; see Section 4.4.
4.6.1.2. Unsuccessful Reservation
This subsection describes the operation where a request for
reservation cannot be satisfied by the RMD-QOSM.
The QNE Ingress, the QNE Interior, and QNE Egress nodes process and
forward the end-to-end RESERVE message and the intra-domain
RESERVE(RMD-QSPEC) message in a similar way, as specified in Section
4.6.1.1. The main difference between the unsuccessful operation and
successful operation is that one of the QNE nodes does not admit the
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request, e.g., due to lack of resources. This also means that the
QNE Edge node MUST NOT forward the end-to-end RESERVE message towards
the QNR node.
Note that the described functionality applies to the RMD reservation-
based methods (see Sections 4.3.1 and 4.3.2) and to the NSIS
measurement-based admission control method (see Section 4.3.2).
The QNE Edge nodes maintain either per-flow QoS-NSLP reservation
states or aggregated QoS-NSLP reservation states. When the QNE Edges
maintain aggregated QoS-NSLP reservation states, the RMD-QOSM
functionality MAY accomplish an RMD modification procedure (see
Section 4.6.1.4), instead of the reservation initiation procedure
that is described in this subsection.
4.6.1.2.1. Operation in the Ingress Nodes
When an end-to-end RESERVE message arrives at the QNE Ingress and if
(1) the "Maximum Packet Size-1 (MPS)" included in the end-to-end QoS
Model <TMOD-1> is larger than this smallest MTU value within the RMD
domain or (2) there are no resources available, the QNE Ingress MUST
reject this end-to-end RESERVE message and send an end-to-end
RESPONSE message back to the sender, as described in the QoS-NSLP
specification, see [RFC5974] and [RFC5975].
When an end-to-end RESPONSE message is received by an Ingress node
(see Section 4.6.1.2.3), the values of the <RII>, <RSN>, <INFO-SPEC>,
and [<QSPEC>] objects are processed according to the QoS-NSLP
procedures.
If the end-to-end RESPONSE message has to be forwarded upstream to a
node outside the RMD-QOSM-aware domain, then the values of the
objects contained in this message (i.e., <RII<, <RSN>, <INFO-SPEC>,
[<QSPEC>]) MUST be set by the QoS-NSLP protocol functions of the QNE.
When an intra-domain RESPONSE message is received by the QNE Ingress
node, which was sent by a QNE Egress (see Section 4.6.1.2.3), it uses
the QoS-NSLP procedures to match it to the intra-domain RESERVE
message that was previously sent. After this phase, the RMD-QSPEC
has to be identified and processed. Note that, in this case, the RMD
Resource Management Function (RMF) is notified that the reservation
has been unsuccessful, by reading the <M> parameter of the PDR
container. Note that when the QNE Edges maintain a per-flow QoS-NSLP
reservation state, the RMD-QOSM functionality, has to start an RMD
release procedure (see Section 4.6.1.5). When the QNE Edges maintain
aggregated QoS-NSLP reservation states, the RMD-QOSM functionality
MAY start an RMD modification procedure (see Section 4.6.1.4).
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4.6.1.2.2. Operation in the Interior Nodes
In the case of the RMD reservation-based scenario, and if the intra-
domain reservation request is not admitted by the QNE Interior node,
then the <Hop_U> and <M> parameters of the PHR container MUST be set
to "1". The <Admitted Hops> counter MUST NOT be increased.
Moreover, the value of the <Max Admitted Hops> counter MUST be set
equal to the <Admitted Hops> value.
Furthermore, the <E> flag associated with the QSPEC <QoS Desired>
object and the <E> flag associated with the local RMD-QSPEC <TMOD-1>
parameter SHOULD be set. In the case of the RMD measurement-based
scenario, the <M> parameter of the PHR container MUST be set to "1".
Furthermore, the <E> flag associated with the QSPEC <QoS Desired>
object and the <E> flag associated with the local RMD-QSPEC <TMOD-1>
parameter SHOULD be set. Note that the <M> flag seems to be set in a
similar way to the <E> flag used by the local RMD-QSPEC <TMOD-1>
parameter. However, the ways in which the two flags are processed by
a QNE are different.
In general, if a QNE Interior node receives an RMD-QSPEC <TMOD-1>
parameter with the <E> flag set and a PHR container type
"PHR_Resource_Request", with the <M> parameter set to "1", then this
"PHR Container" and the RMD-QOSM <QoS Desired> object) MUST NOT be
processed. Furthermore, when the <K> parameter that is included in
the "PHR Container" and carried by a RESERVE message is set to "1",
then this "PHR Container" and the RMD-QOSM <QoS Desired> object) MUST
NOT be processed.
4.6.1.2.3. Operation in the Egress Nodes
In the RMD reservation-based (Section 4.3.3) and RMD NSIS
measurement-based scenarios (Section 4.3.2), when the <M> marked
intra-domain RESERVE(RMD-QSPEC) is received by the QNE Egress node
(see Figure 9), the session associated with the intra-domain
RESERVE(RMD-QSPEC) (the PHB session) and the end-to-end session MUST
be bound.
Moreover, if the initial QSPEC object (used by the end-to-end QoS
Model) used an object combination of type 1 or 2 where the <QoS
Available> is populated, and the intra-domain RESERVE(RMD-QSPEC) was
not successful at all nodes in the RMD domain, i.e., the intra-domain
RESERVE(RMD-QSPEC) message is marked, it MUST be considered that the
<QoS Available> is not satisfied and that the inter-domain (end-to-
end) reservation is considered as to have failed.
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When the QNE Egress uses per-flow intra-domain QoS-NSLP operational
states (see Sections 4.3.2 and 4.3.3), then the QNE Egress node MUST
generate an end-to-end RESPONSE message that has to be sent to its
previous stateful QoS-NSLP hop (see the QoS-NSLP-RMF API described in
[RFC5974]).
* the values of the <RII>, <RSN> and <INFO-SPEC> objects are set by
the standard QoS-NSLP protocol functions. In the case of an
unsuccessful reservation, the <INFO-SPEC> object SHOULD have the
following values:
Error severity class: Transient Failure
Error code value: Reservation failure
The QSPEC that was carried by the end-to-end RESERVE message that
belongs to the same session as this end-to-end RESPONSE message is
included in this message.
In particular, the parameters included in the QSPEC <QoS Reserved>
object of the end-to-end RESPONSE message are copied from the initial
<QoS Desired> values included in its associated end-to-end RESERVE
message. The <E> flag associated with the QSPEC <QoS Reserved>
object and the <E> flag associated with the <TMOD-1> parameter
included in the end-to-end RESPONSE are set.
In addition to the above, similar to the successful operation, see
Section 4.6.1.1.3, the QNE Egress MUST generate an intra-domain
RESPONSE message that has to be sent to its previous stateful QoS-
NSLP hop.
The values of the <RII>, <RSN> and <INFO-SPEC> objects are set by the
standard QoS-NSLP protocol functions. In the case of an unsuccessful
reservation, the <INFO-SPEC> object SHOULD have the following values
(see the QoS-NSLP-RMF API described in [RFC5974]):
Error severity class: Transient Failure
Error code value: Reservation failure
Bader, et al. Experimental [Page 49]
RFC 5977 RMD-QOSM October 2010
QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
RESERVE | | |
--->| | | RESERVE |
|------------------------------------------------------------>|
|RESERVE(RMD-QSPEC:M=0) | |
|------------------->| | |
| |RESERVE(RMD-QSPEC:M=1) |
| |------------------>| |
| | | RESERVE(RMD-QSPEC:M=1)
| | |------------------->|
| |RESPONSE(RMD-QOSM) | |
|<------------------------------------------------------------|
| |RESPONSE | |
|<------------------------------------------------------------|
RESPONSE | | |
<---| | | |
RESERVE(RMD-QSPEC: Tear=1, M=1, <Admitted Hops>=<Max Admitted Hops>
|------------------->| | |
|RESERVE(RMD-QSPEC: Tear=1, M=1, K=1) |
| |------------------>| |
| RESERVE(RMD-QSPEC: Tear=1, M=1, K=1)|
| | |------------------->|
Figure 9: Basic operation during unsuccessful reservation
initiation used by the RMD-QOSM
The values of the RMD-QSPEC MUST be used and/or set in the following
way (see the QoS-NSLP-RMF API described in [RFC5974]):
* the value of the <PDR Control Type> of the PDR container MUST be
set to "23" (PDR_Reservation_Report);
* the value of the <Max Admitted Hops> parameter of the PHR
container included in the received <M> marked intra-domain RESERVE
(RMD-QSPEC) MUST be included in the <Max Admitted Hops> parameter
of the PDR container;
* the value of the <M> parameter of the PDR container MUST be "1".
4.6.1.3. RMD Refresh Reservation
In the case of the RMD measurement-based method, see Section 4.3.2,
QoS-NSLP reservation states in the RMD domain are not typically
maintained, therefore, this method typically does not use an intra-
domain refresh procedure.
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However, there are measurement-based optimization schemes, see
[GrTs03], that MAY use the refresh procedures described in Sections
4.6.1.3.1 and 4.6.1.3.3. However, this measurement-based
optimization scheme can only be applied in the RMD domain if the QNE
Edges are configured to perform intra-domain refresh procedures and
if all the QNE Interior nodes are configured to perform the
measurement-based optimization schemes.
In the description given in this subsection, it is assumed that the
RMD measurement-based scheme does not use the refresh procedures.
When the QNE Edges maintain aggregated or per-flow QoS-NSLP
operational and reservation states (see Sections 4.3.1 and 4.3.3),
then the refresh procedures are very similar. If the RESERVE
messages arrive within the soft state timeout period, the
corresponding number of resource units are not removed. However, the
transmission of the intra-domain and end-to-end (refresh) RESERVE
message are not necessarily synchronized. Furthermore, the
generation of the end-to-end RESERVE message, by the QNE Edges,
depends on the locally maintained refreshed interval (see [RFC5974]).
4.6.1.3.1. Operation in the Ingress Node
The Ingress node MUST be able to generate an intra-domain (refresh)
RESERVE(RMD-QSPEC) at any time defined by the refresh period/timer.
Before generating this message, the RMD QoS signaling model
functionality is using the RMD traffic class (PHR) resource units for
refreshing the RMD traffic class state.
Note that the RMD traffic class refresh periods MUST be equal in all
QNE Edge and QNE Interior nodes and SHOULD be smaller (default: more
than two times smaller) than the refresh period at the QNE Ingress
node used by the end-to-end RESERVE message. The intra-domain
RESERVE (RMD-QSPEC) message MUST include an RMD-QOSM <QoS Desired>
and a PHR container (i.e., PHR_Refresh_Update).
An example of this refresh operation can be seen in Figure 10.
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QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
|RESERVE(RMD-QSPEC) | | |
|------------------->| | |
| |RESERVE(RMD-QSPEC) | |
| |------------------>| |
| | | RESERVE(RMD-QSPEC) |
| | |------------------->|
| | | |
| |RESPONSE(RMD-QSPEC)| |
|<------------------------------------------------------------|
| | | |
Figure 10: Basic operation of RMD-specific refresh procedure
Most of the non-default values of the objects contained in this
message MUST be used and set by the QNE Ingress in the same way as
described in Section 4.6.1.1. The following objects are used and/or
set differently:
* the PHR resource units MUST be included in the <Peak Data Rate-1
(p)> field of the local RMD-QSPEC <TMOD-1> parameter. The <Peak
Data Rate-1 (p)> field value of the local RMD-QSPEC <TMOD-1>
parameter depends on how the different inter-domain (end-to-end)
flows are aggregated by the QNE Ingress node (e.g., the sum of all
the PHR-requested resources of the aggregated flows); see Section
4.3.1. If no QoS-NSLP aggregation is accomplished by the QNE
Ingress node, the <Peak Data Rate-1 (p)> value of the local RMD-
QSPEC <TMOD-1> parameter SHOULD be equal to the <Peak Data Rate-1
(p)> value of the local RMD-QSPEC <TMOD-1> parameter of its
associated new (initial) intra-domain RESERVE (RMD-QSPEC) message;
see Section 4.3.3.
* the value of the Container field of the <PHR Container> MUST be
set to "19", i.e., "PHR_Refresh_Update".
When the intra-domain RESPONSE (RMD-QSPEC) message (see Section
4.6.1.3.3), is received by the QNE Ingress node, then:
* the values of the <RII>, <RSN>, <INFO-SPEC>, and [RFC5975] objects
are processed by the standard QoS-NSLP protocol functions (see
Section 4.6.1.1);
* the "PDR Container" has to be processed by the RMD-QOSM
functionality in the QNE Ingress node. The RMD-QOSM functionality
is notified by the <PDR M> parameter of the PDR container that the
refresh procedure has been successful or unsuccessful. All
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sessions associated with this RMD-specific refresh session MUST be
informed about the success or failure of the refresh procedure.
(When aggregated QoS-NSLP operational and reservation states are
used (see Section 4.3.1), there will be more than one session.)
In the case of failure, the QNE Ingress node has to generate (in a
standard QoS-NSLP way) an error end-to-end RESPONSE message that
will be sent towards the QNI.
4.6.1.3.2. Operation in the Interior Node
The intra-domain RESERVE (RMD-QSPEC) message is received and
processed by the QNE Interior nodes. Any QNE Edge or QNE Interior
node that receives a <PHR_Refresh_Update> field MUST identify the
traffic class state (PHB) (using the <PHB Class> parameter). Most of
the parameters in this refresh intra-domain RESERVE (RMD-QSPEC)
message MUST be used and/or set by a QNE Interior node in the same
way as described in Section 4.6.1.1.
The following objects are used and/or set differently:
* the <Peak Data Rate-1 (p)> value of the local RMD-QSPEC <TMOD-1>
parameter of the RMD-QOSM <QoS Desired> is used by the QNE
Interior node for refreshing the RMD traffic class state. These
resources (included in the <Peak Data Rate-1 (p)> value of local
RMD-QSPEC <TMOD-1>), if reserved, are added to the currently
reserved resources per PHB and therefore they will become a part
of the per-traffic class (PHB) reservation state (see Sections
4.3.1 and 4.3.3). If the refresh procedure cannot be fulfilled
then the <M> and <S> fields carried by the PHR container MUST be
set to "1".
* furthermore, the <E> flag associated with <QoS Desired> object and
the <E> flag associated with the local RMD-QSPEC <TMOD-1>
parameter SHOULD be set.
Any PHR container of type "PHR_Refresh_Update", and its associated
local RMD-QSPEC <TMOD-1>, whether or not it is marked and independent
of the <E> flag value of the local RMD-QSPEC <TMOD-1> parameter, is
always processed, but marked bits are not changed.
4.6.1.3.3. Operation in the Egress Node
The intra-domain RESERVE(RMD-QSPEC) message is received and processed
by the QNE Egress node. A new intra-domain RESPONSE (RMD-QSPEC)
message is generated by the QNE Egress node and MUST include a PDR
(type PDR_Refresh_Report).
Bader, et al. Experimental [Page 53]
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The (refresh) intra-domain RESPONSE (RMD-QSPEC) message MUST be sent
to the QNE Ingress node, i.e., the previous stateful hop. The
(refresh) intra-domain RESPONSE (RMD-QSPEC) message MUST be
explicitly routed to the QNE Ingress node, i.e., the previous
stateful hop, using the procedures described in Section 4.5.
* the values of the <RII>, <RSN>, and <INFO-SPEC> objects are set by
the standard QoS-NSLP protocol functions, see [RFC5974].
* the value of the <PDR Control Type> parameter of the PDR container
MUST be set "24" (i.e., PDR_Refresh_Report). In case of
successful reservation, the <INFO-SPEC> object SHOULD have the
following values:
Error severity Class: Success
Error code value: Reservation successful
* In the case of unsuccessful reservation the <INFO-SPEC> object
SHOULD have the following values:
Error severity class: Transient Failure
Error code value: Reservation failure
The RMD-QSPEC that was carried by the intra-domain RESERVE belonging
to the same session as this intra-domain RESPONSE is included in the
intra-domain RESPONSE message. The parameters included in the QSPEC
<QoS Reserved> object are copied from the original <QoS Desired>
values. If the reservation is unsuccessful, then the <E> flag
associated with the QSPEC <QoS Reserved> object and the <E> flag
associated with the local RMD-QSPEC <TMOD-1> parameter are set.
Furthermore, the <M> and <S> PDR container bits are set to "1".
4.6.1.4. RMD Modification of Aggregated Reservations
In the case when the QNE Edges maintain QoS-NSLP-aggregated
operational and reservation states and the aggregated reservation has
to be modified (see Section 4.3.1) the following procedure is
applied:
* When the modification request requires an increase of the reserved
resources, the QNE Ingress node MUST include the corresponding
value into the <Peak Data Rate-1 (p)> value of the local RMD-QSPEC
<TMOD-1> parameter of the RMD-QOSM <QoS Desired>, which is sent
together with a "PHR_Resource_Request" control information. If a
QNE Edge or QNE Interior node is not able to reserve the number of
requested resources, the "PHR_Resource_Request" that is associated
with the local RMD-QSPEC <TMOD-1> parameter MUST be <M> marked,
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RFC 5977 RMD-QOSM October 2010
i.e., the <M> bit is set to the value of "1". In this situation,
the RMD-specific operation for unsuccessful reservation will be
applied (see Section 4.6.1.2).
* When the modification request requires a decrease of the reserved
resources, the QNE Ingress node MUST include this value into the
<Peak Data Rate-1 (p)> value of the local RMD-QSPEC <TMOD-1>
parameter of the RMD-QOSM <QoS Desired>. Subsequently, an RMD
release procedure SHOULD be accomplished (see Section 4.6.1.5).
Note that if the complete bandwidth associated with the aggregated
reservation maintained at the QNE Ingress does not have to be
released, then the <TEAR> flag MUST be set to OFF. This is
because the NSLP operational states associated with the aggregated
reservation states at the Edge QNEs MUST NOT be turned off.
However, if the complete bandwidth associated with the aggregated
reservation maintained at the QNE Ingress has to be released, then
the <TEAR> flag MUST be set to ON.
It is important to emphasize that this RMD modification scheme only
applies to the following two RMD-QOSM schemes:
* "per-aggregate RMD reservation-based" in combination with the
"severe congestion handling by the RMD-QOSM refresh" procedure;
* "per-aggregate RMD reservation-based" in combination with the
"severe congestion handling by proportional data packet marking"
procedure.
4.6.1.5. RMD Release Procedure
This procedure is applied to all RMD mechanisms that maintain
reservation states. If a refresh RESERVE message does not arrive at
a QNE Interior node within the refresh timeout period, then the
bandwidth requested by this refresh RESERVE message is not updated.
This means that the reserved bandwidth associated with the reduced
state is decreased in the next refresh period by the amount of the
corresponding bandwidth that has not been refreshed, see Section
4.3.3.
This soft state behavior provides certain robustness for the system
ensuring that unused resources are not reserved for a long time.
Resources can be removed by an explicit release at any time.
However, in the situation that an end-to-end (tear) RESERVE is
retransmitted (see Section 5.2.4 in [RFC5974]), then this message
MUST NOT initiate an intra-domain (tear) RESERVE message. This is
because the amount of bandwidth within the RMD domain associated with
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RFC 5977 RMD-QOSM October 2010
the (tear) end-to-end RESERVE has already been released, and
therefore, this amount of bandwidth within the RMD domain MUST NOT
once again be released.
When the RMD-RMF of a QNE Edge or QNE Interior node processes a
"PHR_Release_Request" PHR container, it MUST identify the <PHB Class>
parameter and estimate the time period that elapsed after the
previous refresh, see also Section 3 of [CsTa05].
This MAY be done by indicating the time lag, say "T_Lag", between the
last sent "PHR_Refresh_Update" and the "PHR_Release_Request" control
information container by the QNE Ingress node, see [RMD1] and
[CsTa05] for more details. The value of "T_Lag" is first normalized
to the length of the refresh period, say "T_period". The ratio
between the "T_Lag" and the length of the refresh period, "T_period",
is calculated. This ratio is then introduced into the <Time Lag>
field of the "PHR_Release_Request". When the above mentioned
procedure of indicating the "T_Lag" is used and when a node (QNE
Egress or QNE Interior) receives the "PHR_Release_Request" PHR
container, it MUST store the arrival time. Then, it MUST calculate
the time difference, "T_diff", between the arrival time and the start
of the current refresh period, "T_period". Furthermore, this node
MUST derive the value of the "T_Lag", from the <Time Lag> parameter.
"T_Lag" can be found by multiplying the value included in the <Time
Lag> parameter with the length of the refresh period, "T_period". If
the derived time lag, "T_Lag", is smaller than the calculated time
difference, "T_diff", then this node MUST decrease the PHB
reservation state with the number of resource units indicated in the
<Peak Data Rate-1 (p)> field of the local RMD-QSPEC <TMOD-1>
parameter of the RMD-QOSM <QoS Desired> that has been sent together
with the "PHR_Release_Request" "PHR Container", but not below zero.
An RMD-specific release procedure can be triggered by an end-to-end
RESERVE with a <TEAR> flag set to ON (see Section 4.6.1.5.1), or it
can be triggered by either an intra-domain RESPONSE, an end-to-end
RESPONSE,
or an end-to-end NOTIFY message that includes a marked (i.e., PDR
<M> and/or PDR <S> parameters are set to ON) "PDR_Reservation_Report"
or "PDR_Congestion_Report" and/or an <INFO-SPEC> object.
4.6.1.5.1. Triggered by a RESERVE Message
This RMD-explicit release procedure can be triggered by a tear
(<TEAR> flag set to ON) end-to-end RESERVE message. When a tear
(<TEAR> flag set ON) end-to-end RESERVE message arrives to the QNE
Ingress, the QNE Ingress node SHOULD process the message in a
standard QoS-NSLP way (see [RFC5974]). In addition to this, the RMD
RMF is notified, as specified in [RFC5974].
Bader, et al. Experimental [Page 56]
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Like the scenario described in Section 4.6.1.1., a bypassing
procedure has to be initiated by the QNE Ingress node. The bypassing
procedure is performed according to the description given in Section
4.4. At the QNE Ingress, the end-to-end RESERVE message is marked,
i.e., modifying the QoS-NSLP default NSLPID value to another NSLPID
predefined value that will be used by the GIST message that carries
the end-to-end RESERVE message to bypass the QNE Interior nodes.
Before generating an intra-domain tear RESERVE, the RMD-QOSM has to
release the requested RMD-QOSM bandwidth from the RMD traffic class
state maintained at the QNE Ingress.
This can be achieved by identifying the traffic class (PHB) and then
subtracting the amount of RMD traffic class requested resources,
included in the <Peak Data Rate-1 (p)> field of the local RMD-QSPEC
<TMOD-1> parameter, from the total reserved amount of resources
stored in the RMD traffic class state. The <Time Lag> is used as
explained in the introductory part of Section 4.6.1.5.
QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
RESERVE | | |
--->| | | RESERVE |
|------------------------------------------------------------>|
|RESERVE(RMD-QSPEC:Tear=1) | |
|------------------->| | |
| |RESERVE(RMD-QSPEC:Tear=1) |
| |------------------->| |
| | RESERVE(RMD-QSPEC:Tear=1)
| | |------------------->|
| | | RESERVE
| | | |-->
Figure 11: Explicit release triggered by RESERVE used by the
RMD-QOSM
After that, the REQUIRED bandwidth is released from the RMD-QOSM
traffic class state at the QNE Ingress, an intra-domain RESERVE (RMD-
QOSM) message has to be generated. The intra-domain RESERVE (RMD-
QSPEC) message MUST include an <RMD QoS object combination> field and
a PHR container, (i.e., "PHR_Release_Request") and it MAY include a
PDR container, (i.e., PDR_Release_Request). An example of this
operation can be seen in Figure 11.
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Most of the non-default values of the objects contained in the tear
intra-domain RESERVE message are set by the QNE Ingress node in the
same way as described in Section 4.6.1.1. The following objects are
set differently (see the QoS-NSLP-RMF API described in [RFC5974]):
* The <RII> object MUST NOT be included in this message. This is
because the QNE Ingress node does not need to receive a response
from the QNE Egress node;
* if the release procedure is not applied for the RMD modification
of aggregated reservation procedure (see Section 4.6.1.4), then
the <TEAR> flag MUST be set to ON;
* the PHR resource units MUST be included into the <Peak Data Rate-1
(p)> value of the local RMD-QSPEC <TMOD-1> parameter of the RMD-
QOSM <QoS Desired>;
* the value of the <Admitted Hops> parameter MUST be set to "1";
* the value of the <Time Lag> parameter of the PHR container is
calculated by the RMD-QOSM functionality (see Section 4.6.1.5) the
value of the <Control Type> parameter of the PHR container is set
to "18" (i.e., PHR_Release_Request).
Any QNE Interior node that receives the combination of the RMD-QOSM
<QoS Desired> object and the "PHR_Release_Request" control
information container MUST identify the traffic class (PHB) and
release the requested resources included in the <Peak Data Rate-1
(p)> value of the local RMD-QSPEC <TMOD-1> parameter. This can be
achieved by subtracting the amount of RMD traffic class requested
resources, included in the <Peak Data Rate-1 (p)> field of the local
RMD-QSPEC <TMOD-1> parameter, from the total reserved amount of
resources stored in the RMD traffic class state. The value of the
<Time Lag> parameter of the "PHR_Release_Request" container is used
during the release procedure as explained in the introductory part of
Section 4.6.1.5.
The intra-domain tear RESERVE (RMD-QSPEC) message is received and
processed by the QNE Egress node. The RMD-QOSM <QoS Desired> and the
"PHR RMD-QOSM control" container (and if available the "PDR
Container") are read and processed by the RMD QoS node.
The value of the <Peak Data Rate-1 (p)> field of the local RMD-QSPEC
<TMOD-1> parameter of the RMD-QOSM <QoS Desired> and the value of the
<Time Lag> field of the PHR container MUST be used by the RMD release
procedure.
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This can be achieved by subtracting the amount of RMD traffic class
requested resources, included in the <Peak Data Rate-1 (p)> field
value of the local RMD-QSPEC <TMOD-1> parameter, from the total
reserved amount of resources stored in the RMD traffic class state.
The end-to-end RESERVE message is forwarded by the next hop (i.e.,
the QNE Egress) only if the intra-domain tear RESERVE (RMD-QSPEC)
message arrives at the QNE Egress node. Furthermore, the QNE Egress
MUST stop the marking process that was used to bypass the QNE
Interior nodes by reassigning the QoS-NSLP default NSLPID value to
the end-to-end RESERVE message (see Section 4.4).
Note that when the QNE Edges maintain aggregated QoS-NSLP reservation
states, the RMD-QOSM functionality MAY start an RMD modification
procedure (see Section 4.6.1.4) that uses the explicit release
procedure, described above in this subsection. Note that if the
complete bandwidth associated with the aggregated reservation
maintained at the QNE Ingress has to be released, then the <TEAR>
flag MUST be set to ON. Otherwise, the <TEAR> flag MUST be set to
OFF, see Section 4.6.1.4.
4.6.1.5.2. Triggered by a Marked RESPONSE or NOTIFY Message
This RMD explicit release procedure can be triggered by either an
intra-domain RESPONSE message with a PDR container carrying among
others the <M> and <S> parameters with values <M>=1 and <S>=0 (see
Section 4.6.1.2), an intra-domain (refresh) RESPONSE message carrying
a PDR container with <M>=1 and <S>=1 (see Section 4.6.1.6.1), or an
end-to-end NOTIFY message (see Section 4.6.1.6) with an <INFO-SPEC>
object with the following values:
Error severity class: Informational
Error code value: Congestion situation
When the aggregated intra-domain QoS-NSLP operational states are
used, an end-to-end NOTIFY message used to trigger an RMD release
procedure MAY contain a PDR container that carries an <M> and an <S>
with values <M>=1 and <S>=1, and a bandwidth value in the <PDR
Bandwidth> parameter included in a "PDR_Refresh_Report" or
"PDR_Congestion_Report" container.
Note that in all explicit release procedures, before generating an
intra-domain tear RESERVE, the RMD-QOSM has to release the requested
RMD-QOSM bandwidth from the RMD traffic class state maintained at the
QNE Ingress. This can be achieved by identifying the traffic class
(PHB) and then subtracting the amount of RMD traffic class requested
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RFC 5977 RMD-QOSM October 2010
resources, included in the <Peak Data Rate-1 (p)> field of the local
RMD-QSPEC <TMOD-1> parameter, from the total reserved amount of
resources stored in the RMD traffic class state.
Figure 12 shows the situation that the intra-domain tear RESERVE is
generated after being triggered by either an intra-domain (refresh)
RESPONSE message that carries a PDR container with <M>=1 and <S>=1 or
by an end-to-end NOTIFY message that does not carry a PDR container,
but an <INFO-SPEC> object. The error code values carried by this
NOTIFY message are:
Error severity class: Informational
Error code value: Congestion situation
Most of the non-default values of the objects contained in the tear
intra-domain RESERVE(RMD-QSPEC) message are set by the QNE Ingress
node in the same way as described in Section 4.6.1.1.
The following objects MUST be used and/or set differently (see the
QoS-NSLP-RMF described in [RFC5974]):
* the value of the <M> parameter of the PHR container MUST be set to
"1".
* the value of the <S> parameter of the "PHR container" MUST be set
to "1".
* the RESERVE message MAY include a PDR container. Note that this
is needed if a bidirectional scenario is used; see Section 4.6.2.
QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
| NOTIFY | | |
|<-------------------------------------------------------|
|RESERVE(RMD-QSPEC:Tear=1,M=1,S=1) | |
| ---------------->|RESERVE(RMD-QSPEC:Tear=1,M=1,S=1) |
| | | |
| |----------------->| |
| | RESERVE(RMD-QSPEC:Tear=1,M=1,S=1)
| | |----------------->|
Figure 12: Basic operation during RMD-explicit release procedure
triggered by NOTIFY used by the RMD-QOSM
Note that if the values of the <M> and <S> parameters included in the
PHR container carried by a intra-domain tear RESERVE(RMD-QOSM) are
set as ((<M>=0 and <S>=1) or (<M>=0 and <S>=0) or (<M>=1 and <S>=1)),
Bader, et al. Experimental [Page 60]
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then the <Max Admitted Hops> value SHOULD NOT be compared to the
<Admitted Hops> value and the value of the <K> field MUST NOT be set.
Any QNE Edge or QNE Interior node that receives the intra-domain tear
RESERVE MUST check the <K> field included in the PHR container. If
the <K> field is "0", then the traffic class state (PHB) has to be
identified, using the <PHB Class> parameter, and the requested
resources included in the <Peak Data Rate-1 (p)> field of the local
RMD-QSPEC <TMOD-1> parameter have to be released.
This can be achieved by subtracting the amount of RMD traffic class
requested resources, included in the <Peak Data Rate-1 (p)> field of
the local RMD-QSPEC <TMOD-1> parameter, from the total reserved
amount of resources stored in the RMD traffic class state. The value
of the <Time Lag> parameter of the PHR field is used during the
release procedure, as explained in the introductory part of Section
4.6.1.5. Afterwards, the QNE Egress node MUST terminate the tear
intra-domain RESERVE(RMD-QSPEC) message.
The RMD-specific release procedure that is triggered by an intra-
domain RESPONSE message with an <M>=1 and <S>=0 PDR container (see
Section 4.6.1.2) generates an intra-domain tear RESERVE message that
uses the combination of the <Max Admitted Hops> and <Admitted_Hops>
fields to calculate and specify when the <K> value carried by the
"PHR Container" can be set. When the <K> field is set, then the "PHR
Container" and the RMD-QOSM <QoS Desired> carried by an intra-domain
tear RESERVE MUST NOT be processed.
The RMD-specific explicit release procedure that uses the combination
of <Max Admitted Hops>, <Admitted_Hops> and <K> fields to release
resources/bandwidth in only a part of the RMD domain, is denoted as
RMD partial release procedure.
This explicit release procedure can be used, for example, during
unsuccessful reservation (see Section 4.6.1.2). When the RMD-
QOSM/QoS-NSLP signaling model functionality of a QNE Ingress node
receives a PDR container with values <M>=1 and <S>=0, of type
"PDR_Reservation_Report", it MUST start an RMD partial release
procedure.
In this situation, after the REQUIRED bandwidth is released from the
RMD-QOSM traffic class state at the QNE Ingress, an intra-domain
RESERVE (RMD-QOSM) message has to be generated. An example of this
operation can be seen in Figure 13.
Most of the non-default values of the objects contained in the tear
intra-domain RESERVE(RMD-QSPEC) message are set by the QNE Ingress
node in the same way as described in Section 4.6.1.1.
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The following objects MUST be used and/or set differently:
* the value of the <M> parameter of the PHR container MUST be set to
"1".
* the RESERVE message MAY include a PDR container.
* the value of the <Max Admitted Hops> carried by the "PHR
Container" MUST be set equal to the <Max Admitted Hops> value
carried by the "PDR Container" (with <M>=1 and <S>=0) carried by
the received intra-domain RESPONSE message that triggers the
release procedure.
Any QNE Edge or QNE Interior node that receives the intra-domain tear
RESERVE has to check the value of the <K> field in the "PHR
Container" before releasing the requested resources.
If the value of the <K> field is "1", then all the QNEs located
downstream, including the QNE Egress, MUST NOT process the carried
"PHR Container" and the RMD-QOSM <QoS Desired> object by the intra-
domain tearing RESERVE.
QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)
Node that marked
PHR_Resource_Request
<PHR> object
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
| | | |
| RESPONSE (RMD-QSPEC: M=1) | |
|<------------------------------------------------------------|
RESERVE(RMD-QSPEC: Tear=1, M=1, <Admit Hops>=<Max Admitted Hops>, K=0)
|------------------->| | |
| |RESERVE(RMD-QSPEC: Tear=1, M=1, K=1) |
| |------------------>| |
| | RESERVE(RMD-QSPEC: Tear=1, M=1, K=1)|
| | |------------------->|
| | | |
Figure 13: Basic operation during RMD explicit release procedure
triggered by RESPONSE used by the RMD-QOSM
If the <K> field value is "0", any QNE Edge or QNE Interior node that
receives the intra-domain tear RESERVE can release the resources by
subtracting the amount of RMD traffic class requested resources,
included in the <Peak Data Rate-1 (p)> field of the local RMD-QSPEC
<TMOD-1> parameter, from the total reserved amount of resources
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stored in the RMD traffic class state. The value of the <Time Lag>
parameter of the PHR field is used during the release procedure as
explained in the introductory part of Section 4.6.1.5.
Furthermore, the QNE MUST perform the following procedures.
If the values of the <M> and <S> parameters included in the
"PHR_Release_Request" PHR container are (<M=1> and <S>=0) then the
<Max Admitted Hops> value MUST be compared with the calculated
<Admitted Hops> value. Note that each time that the intra-domain
tear RESERVE is processed and before being forwarded by a QNE, the
<Admitted Hops> value included in the PHR container is increased by
one.
When these two values are equal, the intra-domain RESERVE(RMD-QSPEC)
that is forwarded further towards the QNE Egress MUST set the <K>
value of the carried "PHR Container" to "1".
The reason for doing this is that the QNE node that is currently
processing this message was the last QNE node that successfully
processed the RMD-QOSM <QoS Desired>) and PHR container of its
associated initial reservation request (i.e., initial intra-domain
RESERVE(RMD-QSPEC) message). Its next QNE downstream node was unable
to successfully process the initial reservation request; therefore,
this QNE node marked the <M> and <Hop_U> parameters of the
"PHR_Resource_Request".
Finally, note that the QNE Egress node MUST terminate the intra-
domain RESERVE(RMD-QSPEC) message.
Moreover, note that the above described RMD partial release procedure
applies to the situation that the QNE Edges maintain a per-flow QoS-
NSLP reservation state.
When the QNE Edges maintain aggregated intra-domain QoS-NSLP
operational states and a severe congestion occurs, then the QNE
Ingress MAY receive an end-to-end NOTIFY message (see Section
4.6.1.6) with a PDR container that carries the <M>=0 and <S>=1 fields
and a bandwidth value in the <PDR Bandwidth> parameter included in a
"PDR_Congestion_Report" container. Furthermore, the same end-to-end
NOTIFY message carries an <INFO-SPEC> object with the following
values:
Error severity class: Informational
Error code value: Congestion situation
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The end-to-end session associated with this NOTIFY message maintains
the BOUND-SESSION-ID of the bound aggregated session; see Section
4.3.1. The RMD-QOSM at the QNE Ingress MUST start an RMD
modification procedures (see Section 4.6.1.4) that uses the RMD
explicit release procedure, described above in this section. In
particular, the RMD explicit release procedure releases the bandwidth
value included in the <PDR Bandwidth> parameter, within the
"PDR_Congestion_Report" container, from the reserved bandwidth
associated with the aggregated intra-domain QoS-NSLP operational
state.
4.6.1.6. Severe Congestion Handling
This section describes the operation of the RMD-QOSM when a severe
congestion occurs within the Diffserv domain.
When a failure in a communication path, e.g., a router or a link
failure occurs, the routing algorithms will adapt to failures by
changing the routing decisions to reflect changes in the topology and
traffic volume. As a result, the rerouted traffic will follow a new
path, which MAY result in overloaded nodes as they need to support
more traffic. This MAY cause severe congestion in the communication
path. In this situation, the available resources, are not enough to
meet the REQUIRED QoS for all the flows along the new path.
Therefore, one or more flows SHOULD be terminated, or forwarded in a
lower priority queue.
Interior nodes notify Edge nodes by data marking or marking the
refresh messages.
4.6.1.6.1. Severe Congestion Handling by the RMD-QOSM Refresh Procedure
This procedure applies to all RMD scenarios that use an RMD refresh
procedure. The QoS-NSLP and RMD are able to cope with congested
situations using the refresh procedure; see Section 4.6.1.3.
If the refresh is not successful in an QNE Interior node, Edge nodes
are notified by setting <S>=1 (<M>=1) marking the refresh messages
and by setting the <O> field in the "PHR_Refresh_Update" container,
carried by the intra-domain RESERVE message.
Note that the overload situation can be detected by using the example
given in Appendix A.1. In this situation, when the given
signaled_overload_rate parameter given in Appendix A.1 is higher than
0, the value of the <Overload> field is set to "1". The calculation
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of this is given in Appendix A.1 and denoted as the
signaled_overload_rate parameter. The flows can be terminated by the
RMD release procedure described in Section 4.6.1.5.
The intra-domain RESPONSE message that is sent by the QNE Egress
towards the QNE Ingress will contain a PDR container with a Parameter
ID = 26, i.e., "PDR_Congestion_Report". The values of the <M>, <S>,
and <O> fields of this container SHOULD be set equal to the values of
the <M>, <S>, and <O> fields, respectively, carried by the
"PHR_Refresh_Update" container. Part of the flows, corresponding to
the <O>, are terminated, or forwarded in a lower priority queue.
The flows can be terminated by the RMD release procedure described in
Section 4.6.1.5.
Furthermore, note that the above functionalities also apply to the
scenario in which the QNE Edge nodes maintain either per-flow QoS-
NSLP reservation states or aggregated QoS-NSLP reservation states.
In general, relying on the soft state refresh mechanism solves the
congestion within the time frame of the refresh period. If this
mechanism is not fast enough, additional functions SHOULD be used,
which are described in Section 4.6.1.6.2.
4.6.1.6.2. Severe Congestion Handling by Proportional Data Packet
Marking
This severe congestion handling method requires the following
functionalities.
4.6.1.6.2.1. Operation in the Interior Nodes
The detection and marking/re-marking functionality described in this
section applies to NSIS-aware and NSIS-unaware nodes. This means
however, that the "not NSIS-aware" nodes MUST be configured such that
they can detect the congestion/severe congestion situations and re-
mark packets in the same way the "NSIS-aware" nodes do.
The Interior node detecting severe congestion re-marks data packets
passing the node. For this re-marking, two additional DSCPs can be
allocated for each traffic class. One DSCP MAY be used to indicate
that the packet passed a congested node. This type of DSCP is
denoted in this document as an "affected DSCP" and is used to
indicate that a packet passed through a severe congested node.
The use of this DSCP type eliminates the possibility that, e.g., due
to flow-based ECMP-enabled (Equal Cost Multiple Paths) routing, the
Egress node either does not detect packets passed a severely
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congested node or erroneously detects packets that actually did not
pass the severely congested node. Note that this type of DSCP MUST
only be used if all the nodes within the RMD domain are configured to
use it. Otherwise, this type of DSCP MUST NOT be applied. The other
DSCP MUST be used to indicate the degree of congestion by marking the
bytes proportionally to the degree of congestion. This type of DSCP
is denoted in this document as "encoded DSCP".
In this document, note that the terms "marked packets" or "marked
bytes" refer to the "encoded DSCP". The terms "unmarked packets" or
"unmarked bytes" represent the packets or the bytes belonging to
these packets that their DSCP is either the "affected DSCP" or the
original DSCP. Furthermore, in the algorithm described below, it is
considered that the router MAY drop received packets. The
counting/measuring of marked or unmarked bytes described in this
section is accomplished within measurement periods. All nodes within
an RMD domain use the same, fixed-measurement interval, say T
seconds, which MUST be preconfigured.
It is RECOMMENDED that the total number of additional (local and
experimental) DSCPs needed for severe congestion handling within an
RMD domain SHOULD be as low as possible, and it SHOULD NOT exceed the
limit of 8. One possibility to reduce the number of used DSCPs is to
use only the "encoded DSCP" and not to use "affected DSCP" marking.
Another possible solution is, for example, to allocate one DSCP for
severe congestion indication for each of the AF classes that can be
supported by RMD-QOSM.
An example of a re-marking procedure can be found in Appendix A.1.
4.6.1.6.2.2. Operation in the Egress Nodes
When the QNE Edges maintain a per-flow intra-domain QoS-NSLP
operational state (see Sections 4.3.2 and 4.3.3), then the following
procedure is followed. The QNE Egress node applies a predefined
policy to solve the severe congestion situation, by selecting a
number of inter-domain (end-to-end) flows that SHOULD be terminated
or forwarded in a lower priority queue.
When the RMD domain does not use the "affected DSCP" marking, the
Egress MUST generate an Ingress/Egress pair aggregated state, for
each Ingress and for each supported PHB. This is because the Edges
MUST be able to detect in which Ingress/Egress pair a severe
congestion occurs. This is because, otherwise, the QNE Egress will
not have any information on which flows or groups of flows were
affected by the severe congestion.
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When the RMD domain supports the "affected DSCP" marking, the Egress
is able to detect all flows that are affected by the severe
congestion situation. Therefore, when the RMD domain supports the
"affected DSCP" marking, the Egress MAY not generate and maintain the
Ingress/Egress pair aggregated reservation states. Note that these
aggregated reservation states MAY not be associated with aggregated
intra-domain QoS-NSLP operational states.
The Ingress/Egress pair aggregated reservation state can be derived
by detecting which flows are using the same PHB and are sent by the
same Ingress (via the per-flow end-to-end QoS-NSLP states).
Some flows, belonging to the same PHB traffic class might get other
priority than other flows belonging to the same PHB traffic class.
This difference in priority can be notified to the Egress and Ingress
nodes by either the RESERVE message that carries the QSPEC associated
with the end-to-end QoS Model, e.g.,, <Preemption Priority> and
<Defending Priority> parameter or using a locally defined policy.
The priority value is kept in the reservation states (see Section
4.3), which might be used during admission control and/or severe
congestion handling procedures. The terminated flows are selected
from the flows having the same PHB traffic class as the PHB of the
marked (as "encoded DSCP") and "affected DSCP" (when applied in the
complete RMD domain) packets and (when the Ingress/Egress pair
aggregated states are available) that belong to the same
Ingress/Egress pair aggregate.
For flows associated with the same PHB traffic class, the priority of
the flow plays a significant role. An example of calculating the
number of flows associated with each priority class that have to be
terminated is explained in Appendix A.2.
For the flows (sessions) that have to be terminated, the QNE Egress
node generates and sends an end-to-end NOTIFY message to the QNE
Ingress node (its upstream stateful QoS-NSLP peer) to indicate the
severe congestion in the communication path.
The non-default values of the objects contained in the NOTIFY message
MUST be set by the QNE Egress node as follows (see QoS-NSLP-RMF API
described in [RFC5974]):
* the values of the <INFO-SPEC> object is set by the standard QoS-
NSLP protocol functions.
* the <INFO-SPEC> object MUST include information that notifies that
the end-to-end flow MUST be terminated. This information is as
follows:
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RFC 5977 RMD-QOSM October 2010
Error severity class: Informational
Error code value: Congestion situation
When the QNE Edges maintain a per-aggregate intra-domain QoS-NSLP
operational state (see Section 4.3.1), the QNE Edge has to
calculate, per each aggregate intra-domain QoS-NSLP operational
state, the total bandwidth that has to be terminated in order to
solve the severe congestion. The total bandwidth to be released
is calculated in the same way as in the situation in which the QNE
Edges maintain per-flow intra-domain QoS-NSLP operational states.
Note that for the aggregated sessions that are affected, the QNE
Egress node generates and sends one end-to-end NOTIFY message to
the QNE Ingress node (its upstream stateful QoS-NSLP peer) to
indicate the severe congestion in the communication path. Note
that this end-to-end NOTIFY message is associated with one of the
end-to-end sessions that is bound to the aggregated intra-domain
QoS-NSLP operational state.
The non-default values of the objects contained in the NOTIFY
message MUST be set by the QNE Egress node in the same way as the
ones used by the end-to-end NOTIFY message described above for the
situation that the QNE Egress maintains a per-flow intra-domain
operational state. In addition to this, the end-to-end NOTIFY
MUST carry the RMD-QSPEC, which contains a PDR container with a
Parameter ID = 26, i.e., "PDR_Congestion_Report". The value of
the <S> SHOULD be set. Furthermore, the value of the <PDR
Bandwidth> parameter MUST contain the bandwidth associated with
the aggregated QoS-NSLP operational state, which has to be
released.
Furthermore, the number of end-to-end sessions that have to be
terminated will be calculated as in the situation that the QNE
Edges maintain per-flow intra-domain QoS-NSLP operational states.
Similarly for each, to be terminated, ongoing flow, the Egress
will notify the Ingress in the same way as in the situation that
the QNE Edges maintain per-flow intra-domain QoS-NSLP operational
states.
Note that the QNE Egress SHOULD restore the original <DSCP> values
of the re-marked packets; otherwise, multiple actions for the same
event might occur. However, this value MAY be left in its re-
marking form if there is an SLA agreement between domains that a
downstream domain handles the re-marking problem.
An example of a detailed severe congestion operation in the Egress
Nodes can be found in Appendix A.2.
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4.6.1.6.2.3. Operation in the Ingress Nodes
Upon receiving the (end-to-end) NOTIFY message, the QNE Ingress node
resolves the severe congestion by a predefined policy, e.g., by
refusing new incoming flows (sessions), terminating the affected and
notified flows (sessions), and blocking their packets or shifting
them to an alternative RMD traffic class (PHB).
This operation is depicted in Figure 14, where the QNE Ingress, for
each flow (session) to be terminated, receives a NOTIFY message that
carries the "Congestion situation" error code.
When the QNE Ingress node receives the end-to-end NOTIFY message, it
associates this NOTIFY message with its bound intra-domain session
(see Sections 4.3.2 and 4.3.3) via the BOUND-SESSION-ID information
included in the end-to-end per-flow QoS-NSLP state. The QNE Ingress
uses the operation described in Section 4.6.1.5.2 to terminate the
intra-domain session.
QNE(Ingress) QNE(Interior) QNE(Interior) QNE(Egress)
user | | | |
data | user data | | |
------>|----------------->| user data | user data |
| |---------------->S(# marked bytes) |
| | S----------------->|
| | S(# unmarked bytes)|
| | S----------------->|Term.
| NOTIFY S |flow?
|<-----------------|-----------------S------------------|YES
|RESERVE(RMD-QSPEC:Tear=1,M=1,S=1) S |
| ---------------->|RESERVE(RMD-QSPEC:T=1,M=1,S=1) |
| | S |
| |---------------->S |
| | RESERVE(RMD-QSPEC:Tear=1,M=1,S=1)
| | S----------------->|
Figure 14: RMD severe congestion handling
Note that the above functionality applies to the RMD reservation-
based (see Section 4.3.3) and to both measurement-based admission
control methods (i.e., congestion notification based on probing and
the NSIS measurement-based admission control; see Section 4.3.2).
In the case that the QNE Edges support aggregated intra-domain QoS-
NSLP operational states, the following actions take place. The QNE
Ingress MAY receive an end-to-end NOTIFY message with a PDR container
that carries an <S> marked and a bandwidth value in the <PDR
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Bandwidth> parameter included in a "PDR_Congestion_Report" container.
Furthermore, the same end-to-end NOTIFY message carries an <INFO-
SPEC> object with the "Congestion situation" error code.
When the QNE Ingress node receives this end-to-end NOTIFY message, it
associates the NOTIFY message with the aggregated intra-domain QoS-
NSLP operational state via the BOUND-SESSION-ID information included
in the end-to-end per-flow QoS-NSLP operational state, see Section
4.3.1.
The RMD-QOSM at the QNE Ingress node by using the total bandwidth
value to be released included in the <PDR Bandwidth> parameter MUST
reduce the bandwidth associated and reserved by the RMD aggregated
session. This is accomplished by triggering the RMD modification for
aggregated reservations procedure described in Section 4.6.1.4.
In addition to the above, the QNE Ingress MUST select a number of
inter-domain (end-to-end) flows (sessions) that MUST be terminated.
This is accomplished in the same way as in the situation that the QNE
Edges maintain per-flow intra-domain QoS-NSLP operational states.
The terminated end-to-end sessions are selected from the end-to-end
sessions bound to the aggregated intra-domain QoS-NSLP operational
state. Note that the end-to-end session associated with the received
end-to-end NOTIFY message that notified the severe congestion MUST
also be selected for termination.
For the flows (sessions) that have to be terminated, the QNE Ingress
node generates and sends an end-to-end NOTIFY message upstream
towards the sender (QNI). The values carried by this message are:
* the values of the <INFO-SPEC> object set by the standard QoS-NSLP
protocol functions.
* the <INFO-SPEC> object MUST include information that notifies that
the end-to-end flow MUST be terminated. This information is as
follows:
Error severity class: Informational
Error code value: Congestion situation
4.6.1.7. Admission Control Using Congestion Notification Based on
Probing
The congestion notification function based on probing can be used to
implement a simple measurement-based admission control within a
Diffserv domain. At Interior nodes along the data path, congestion
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notification thresholds are set in the measurement-based admission
control function for the traffic belonging to different PHBs. These
Interior nodes are not NSIS-aware nodes.
4.6.1.7.1. Operation in Ingress Nodes
When an end-to-end reservation request (RESERVE) arrives at the
Ingress node (QNE), see Figure 15, it is processed based on the
procedures defined by the end-to-end QoS Model.
The <DSCP> field of the GIST datagram message that is used to
transport this probe RESERVE message, SHOULD be marked with the same
value of DSCP as the data path packets associated with the same
session. In this way, it is ensured that the end-to-end RESERVE
(probe) packet passed through the node that it is congested. This
feature is very useful when ECMP-based routing is used to detect only
flows that are passing through the congested router.
When a (end-to-end) RESPONSE message is received by the Ingress
node,it will be processed based on the procedures defined by the end-
to-end QoS Model.
4.6.1.7.2. Operation in Interior nodes
These Interior nodes do not need to be NSIS-aware nodes and they do
not need to process the NSIS functionality of NSIS messages. Note
that the "not NSIS-aware" nodes MUST be configured such that they can
detect the congestion/severe congestion situations and re-mark
packets in the same way the "NSIS-aware" nodes do.
Using standard functionalities, congestion notification thresholds
are set for the traffic that belongs to different PHBs (see Section
4.3.2). The end-to-end RESERVE message, see Figure 15, is used as a
probe packet.
The <DSCP> field of all data packets and of the GIST message carrying
the RESERVE message will be re-marked when the corresponding
"congestion notification" threshold is exceeded (see Section 4.3.2).
Note that when the data rate is higher than the congestion
notification threshold, the data packets are also re-marked. An
example of the detailed operation of this procedure is given in
Appendix A.2.
4.6.1.7.3. Operation in Egress Nodes
As emphasized in Section 4.6.1.6.2.2, the Egress node, by using the
per-flow end-to-end QoS-NSLP states, can derive which flows are using
the same PHB and are sent by the same Ingress.
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For each Ingress, the Egress SHOULD generate an Ingress/Egress pair
aggregated (RMF) reservation state for each supported PHB. Note that
this aggregated reservation state does not require that an aggregated
intra-domain QoS-NSLP operational state is needed also.
Appendix A.4 contains an example of how and when a (probe) RESERVE
message that arrives at the Egress is admitted or rejected.
If the request is rejected, then the Egress node SHOULD generate an
(end-to-end) RESPONSE message to notify that the reservation is
unsuccessful. In particular, it will generate an <INFO-SPEC> object
of:
Error severity class: Transient Failure
Error code value: Reservation failure
The QSPEC that was carried by the end-to-end RESERVE that belongs to
the same session as this end-to-end RESPONSE is included in this
message. The parameters included in the QSPEC <QoS Reserved> object
are copied from the original <QoS Desired> values. The <E> flag
associated with the <QoS Reserved> object and the <E> flag associated
with local RMD-QSPEC <TMOD-1> parameter are also set. This RESPONSE
message will be sent to the Ingress node and it will be processed
based on the end-to-end QoS Model.
Note that the QNE Egress SHOULD restore the original <DSCP> values of
the re-marked packets; otherwise, multiple actions for the same event
might occur. However, this value MAY be left in its re-marking form
if there is an SLA agreement between domains that a downstream domain
handles the re-marking problem. Note that the break <B> flag carried
by the end-to-end RESERVE message MUST NOT be set.
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QNE(Ingress) Interior Interior QNE(Egress)
(not NSIS aware) (not NSIS aware)
user | | | |
data | user data | | |
------>|----------------->| user data | |
| |---------------->| user data |
| | |----------------->|
user | | | |
data | user data | | |
------>|----------------->| user data | user data |
| |---------------->S(# marked bytes) |
| | S----------------->|
| | S(# unmarked bytes)|
| | S----------------->|
| | S |
RESERVE | | S |
------->| | S |
|----------------------------------->S |
| | RESERVE(re-marked DSCP in GIST)
| | S----------------->|
| |RESPONSE(unsuccessful INFO-SPEC) |
|<------------------------------------------------------|
RESPONSE(unsuccessful INFO-SPEC) | |
<------| | | |
Figure 15: Using RMD congestion notification function for
admission control based on probing
4.6.2. Bidirectional Operation
This section describes the basic bidirectional operation and sequence
of events/triggers of the RMD-QOSM. The following basic operation
cases are distinguished:
* Successful and unsuccessful reservation (Section 4.6.2.1);
* Refresh reservation (Section 4.6.2.2);
* Modification of aggregated reservation (Section 4.6.2.3);
* Release procedure (Section 4.6.2.4);
* Severe congestion handling (Section 4.6.2.5);
* Admission control using congestion notification based on probing
(Section 4.6.2.6).
It is important to emphasize that the content of this section is used
for the specification of the following RMD-QOSM/QoS-NSLP signaling
schemes, when basic unidirectional operation is assumed:
* "per-flow congestion notification based on probing";
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* "per-flow RMD NSIS measurement-based admission control",
* "per-flow RMD reservation-based" in combination with the "severe
congestion handling by the RMD-QOSM refresh" procedure;
* "per-flow RMD reservation-based" in combination with the "severe
congestion handling by proportional data packet marking"
procedure;
* "per-aggregate RMD reservation-based" in combination with the
"severe congestion handling by the RMD-QOSM refresh" procedure;
* "per-aggregate RMD reservation-based" in combination with the
"severe congestion handling by proportional data packet marking"
procedure.
For more details, please see Section 3.2.3.
In particular, the functionality described in Sections 4.6.2.1,
4.6.2.2, 4.6.2.3, 4.6.2.4, and 4.6.2.5 applies to the RMD
reservation-based and NSIS measurement-based admission control
methods. The described functionality in Section 4.6.2.6 applies to
the admission control procedure that uses the congestion notification
based on probing. The QNE Edge nodes maintain either per-flow QoS-
NSLP operational and reservation states or aggregated QoS-NSLP
operational and reservation states.
RMD-QOSM assumes that asymmetric routing MAY be applied in the RMD
domain. Combined sender-receiver initiated reservation cannot be
efficiently done in the RMD domain because upstream NTLP states are
not stored in Interior routers.
Therefore, the bidirectional operation SHOULD be performed by two
sender-initiated reservations (sender&sender). We assume that the
QNE Edge nodes are common for both upstream and downstream
directions, therefore, the two reservations/sessions can be bound at
the QNE Edge nodes. Note that if this is not the case, then the
bidirectional procedure could be managed and maintained by nodes
located outside the RMD domain, by using other procedures than the
ones defined in RMD-QOSM.
This (intra-domain) bidirectional sender&sender procedure can then be
applied between the QNE Edge (QNE Ingress and QNE Egress) nodes of
the RMD QoS signaling model. In the situation in which a security
association exists between the QNE Ingress and QNE Egress nodes (see
Figure 15), and the QNE Ingress node has the REQUIRED <Peak Data
Rate-1 (p)> values of the local RMD-QSPEC <TMOD-1> parameters for
both directions, i.e., QNE Ingress towards QNE Egress and QNE Egress
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towards QNE Ingress, then the QNE Ingress MAY include both <Peak Data
Rate-1 (p)> values of the local RMD-QSPEC <TMOD-1> parameters (needed
for both directions) into the RMD-QSPEC within a RESERVE message. In
this way, the QNE Egress node is able to use the QoS parameters
needed for the "Egress towards Ingress" direction (QoS-2). The QNE
Egress is then able to create a RESERVE with the right QoS parameters
included in the QSPEC, i.e., RESERVE (QoS-2). Both directions of the
flows are bound by inserting <BOUND-SESSION-ID> objects at the QNE
Ingress and QNE Egress, which will be carried by bound end-to-end
RESERVE messages.
|------ RESERVE (QoS-1, QoS-2)----|
| V
| Interior/stateless QNEs
+---+ +---+
|------->|QNE|-----|QNE|------
| +---+ +---+ |
| V
+---+ +---+
|QNE| |QNE|
+---+ +---+
^ |
| | +---+ +---+ V
| |-------|QNE|-----|QNE|-----|
| +---+ +---+
Ingress/ Egress/
stateful QNE stateful QNE
|
<--------- RESERVE (QoS-2) -------|
Figure 16: The intra-domain bidirectional reservation scenario
in the RMD domain
Note that it is RECOMMENDED that the QNE implementations of RMD-QOSM
process the QoS-NSLP signaling messages with a higher priority than
data packets. This can be accomplished as described in Section 3.3.4
in [RFC5974] and the QoS-NSLP-RMF API [RFC5974].
A bidirectional reservation, within the RMD domain, is indicated by
the PHR <B> and PDR <B> flags, which are set in all messages. In
this case, two <BOUND-SESSION-ID> objects SHOULD be used.
When the QNE Edges maintain per-flow intra-domain QoS-NSLP
operational states, the end-to-end RESERVE message carries two BOUND-
SESSION-IDs. One BOUND-SESSION-ID carries the SESSION-ID of the
tunneled intra-domain (per-flow) session that is using a Binding_Code
with value set to code (Tunneled and end-to-end sessions). Another
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BOUND-SESSION-ID carries the SESSION-ID of the bound bidirectional
end-to-end session. The Binding_Code associated with this BOUND-
SESSION-ID is set to code (Bidirectional sessions).
When the QNE Edges maintain aggregated intra-domain QoS-NSLP
operational states, the end-to-end RESERVE message carries two BOUND-
SESSION-IDs. One BOUND-SESSION-ID carries the SESSION-ID of the
tunneled aggregated intra-domain session that is using a Binding_Code
with value set to code (Aggregated sessions). Another BOUND-SESSION-
ID carries the SESSION-ID of the bound bidirectional end-to-end
session. The Binding_Code associated with this BOUND-SESSION-ID is
set to code (Bidirectional sessions).
The intra-domain and end-to-end QoS-NSLP operational states are
initiated/modified depending on the binding type (see Sections 4.3.1,
4.3.2, and 4.3.3).
If no security association exists between the QNE Ingress and QNE
Egress nodes, the bidirectional reservation for the sender&sender
scenario in the RMD domain SHOULD use the scenario specified in
[RFC5974] as "bidirectional reservation for sender&sender scenario".
This is because in this scenario, the RESERVE message sent from the
QNE Ingress to QNE Egress does not have to carry the QoS parameters
needed for the "Egress towards Ingress" direction (QoS-2).
In the following sections, it is considered that the QNE Edge nodes
are common for both upstream and downstream directions and therefore,
the two reservations/sessions can be bound at the QNE Edge nodes.
Furthermore, it is considered that a security association exists
between the QNE Ingress and QNE Egress nodes, and the QNE Ingress
node has the REQUIRED <Peak Data Rate-1 (p)> value of the local RMD-
QSPEC <TMOD-1> parameters for both directions, i.e., QNE Ingress
towards QNE Egress and QNE Egress towards QNE Ingress.
According to Section 3.2.3, it is specified that only the "per-flow
RMD reservation-based" in combination with the "severe congestion
handling by proportional data packet marking" scheme MUST be
implemented within one RMD domain. However, all RMD QNEs supporting
this specification MUST support the combination the "per-flow RMD
reservation-based" in combination with the "severe congestion
handling by proportional data packet marking" scheme. If the RMD
QNEs support more RMD-QOSM schemes, then the operator of that RMD
domain MUST preconfigure all the QNE Edge nodes within one domain
such that the <SCH> field included in the "PHR Container" (Section
4.1.2) and the "PDR Container" (Section 4.1.3) will always use the
same value, such that within one RMD domain, only one of the below
described RMD-QOSM schemes is used at a time.
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All QNE nodes located within the RMD domain MUST read and interpret
the <SCH> field included in the "PHR Container" before processing all
the other <PHR Container> payload fields. Moreover, all QNE Edge
nodes located at the boarder of the RMD domain, MUST read and
interpret the <SCH> field included in the "PDR container" before
processing all the other <PDR Container> payload fields.
4.6.2.1. Successful and Unsuccessful Reservations
This section describes the operation of the RMD-QOSM where an RMD
Intra-domain bidirectional reservation operation, see Figure 16 and
Section 4.6.2, is either successfully or unsuccessfully accomplished.
The bidirectional successful reservation is similar to a combination
of two unidirectional successful reservations that are accomplished
in opposite directions, see Figure 17. The main differences of the
bidirectional successful reservation procedure with the combination
of two unidirectional successful reservations accomplished in
opposite directions are as follows. Note also that the intra-domain
and end-to-end QoS-NSLP operational states generated and maintained
by the end-to-end RESERVE messages contain, compared to the
unidirectional reservation scenario, a different BOUND-SESSION-ID
data structure (see Sections 4.3.1, 4.3.2, and 4.3.3). In this
scenario, the intra-domain RESERVE message sent by the QNE Ingress
node towards the QNE Egress node is denoted in Figure 17 as RESERVE
(RMD-QSPEC): "forward". The main differences between the intra-
domain RESERVE (RMD-QSPEC): "forward" message used for the
bidirectional successful reservation procedure and a RESERVE (RMD-
QSPEC) message used for the unidirectional successful reservation are
as follows (see the QoS-NSLP-RMF API described in [RFC5974]):
* the <RII> object MUST NOT be included in the message. This is
because no RESPONSE message is REQUIRED.
* the <B> bit of the PHR container indicates a bidirectional
reservation and it MUST be set to "1".
* the PDR container is also included in the RESERVE(RMD-QSPEC):
"forward" message. The value of the Parameter ID is "20", i.e.,
"PDR_Reservation_Request". Note that the response PDR container
sent by a QNE Egress to a QNE Ingress node is not carried by an
end-to-end RESPONSE message, but it is carried by an intra-domain
RESERVE message that is sent by the QNE Egress node towards the
QNE Ingress node (denoted in Figure 16 as RESERVE(RMD-QSPEC):
"reverse").
* the <B> PDR bit indicates a bidirectional reservation and is set
to "1".
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* the <PDR Bandwidth> field specifies the requested bandwidth that
has to be used by the QNE Egress node to initiate another intra-
domain RESERVE message in the reverse direction.
The RESERVE(RMD-QSPEC): "reverse" message is initiated by the QNE
Egress node at the moment that the RESERVE(RMD-QSPEC): "forward"
message is successfully processed by the QNE Egress node.
The main differences between the RESERVE(RMD-QSPEC): "reverse"
message used for the bidirectional successful reservation procedure
and a RESERVE(RMD-QSPEC) message used for the unidirectional
successful reservation are as follows:
QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress)
NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful
| | | | |
| | | | |
|RESERVE(RMD-QSPEC) | | |
|"forward" | | | |
| | RESERVE(RMD-QSPEC): | |
|--------------->| "forward" | | |
| |------------------------------>| |
| | | |------------->|
| | | | |
| | |RESERVE(RMD-QSPEC) |
| RESERVE(RMD-QSPEC) | "reverse" |<-------------|
| "reverse" | |<--------------| |
|<-------------------------------| | |
Figure 17: Intra-domain signaling operation for successful
bidirectional reservation
* the <RII> object is not included in the message. This is because
no RESPONSE message is REQUIRED;
* the value of the <Peak Data Rate-1 (p)> field of the local RMD-
QSPEC <TMOD-1> parameter is set equal to the value of the <PDR
Bandwidth> field included in the RESERVE(RMD-QSPEC): "forward"
message that triggered the generation of this RESERVE(RMD-QSPEC):
"reverse" message;
* the <B> bit of the PHR container indicates a bidirectional
reservation and is set to "1";
* the PDR container is included into the RESERVE(RMD-QSPEC):
"reverse" message. The value of the Parameter ID is "23", i.e.,
"PDR_Reservation_Report";
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* the <B> PDR bit indicates a bidirectional reservation and is set
to "1".
Figures 18 and 19 show the flow diagrams used in the case of an
unsuccessful bidirectional reservation. In Figure 18, the QNE that
is not able to support the requested <Peak Data Rate-1 (p)> value of
local RMD-QSPEC <TMOD-1> is located in the direction QNE Ingress
towards QNE Egress. In Figure 19, the QNE that is not able to
support the requested <Peak Data Rate-1 (p)> value of local RMD-QSPEC
<TMOD-1> is located in the direction QNE Egress towards QNE Ingress.
The main differences between the bidirectional unsuccessful procedure
shown in Figure 18 and the bidirectional successful procedure are as
follows:
* the QNE node that is not able to reserve resources for a certain
request is located in the "forward" path, i.e., the path from the
QNE Ingress towards the QNE Egress.
* the QNE node that is not able to support the requested <Peak Data
Rate-1 (p)> value of local RMD-QSPEC <TMOD-1> MUST mark the <M>
bit, i.e., set to value "1", of the RESERVE(RMD-QSPEC): "forward".
QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress)
NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful
| | | | |
|RESERVE(RMD-QSPEC): | | |
| "forward" | RESERVE(RMD-QSPEC): | |
|--------------->| "forward" | M RESERVE(RMD-QSPEC):
| |--------------------------->M "forward-M marked"
| | | M-------------->|
| | RESPONSE(PDR) M |
| | "forward - M marked"M |
|<------------------------------------------------------------|
|RESERVE(RMD-QSPEC, K=0) | M |
|"forward - T tear" | M |
|--------------->| | M |
| RESERVE(RMD-QSPEC, K=1) M |
| | "forward - T tear" M |
| |--------------------------->M |
| | RESERVE(RMD-QSPEC, K=1) |
| | "forward - T tear" |
| | M-------------->|
Figure 18: Intra-domain signaling operation for unsuccessful
bidirectional reservation (rejection on path
QNE(Ingress) towards QNE(Egress))
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The operation for this type of unsuccessful bidirectional reservation
is similar to the operation for unsuccessful unidirectional
reservation, shown in Figure 9.
The main differences between the bidirectional unsuccessful procedure
shown in Figure 19 and the in bidirectional successful procedure are
as follows:
* the QNE node that is not able to reserve resources for a certain
request is located in the "reverse" path, i.e., the path from the
QNE Egress towards the QNE Ingress.
* the QNE node that is not able to support the requested <Peak Data
Rate-1 (p)> value of local RMD-QSPEC <TMOD-1> MUST mark the <M>
bit, i.e., set to value "1", the RESERVE(RMD-QSPEC): "reverse".
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QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress)
NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful
| | | | |
|RESERVE(RMD-QSPEC) | | |
|"forward" | RESERVE(RMD-QSPEC): | |
|--------------->| "forward" | RESERVE(RMD-QSPEC): |
| |-------------------------------->|"forward" |
| | RESERVE(RMD-QSPEC): |------------->|
| | "reverse" | | |
| | RESERVE(RMD-QSPEC) | |
| RESERVE(RMD-QSPEC): M "reverse" |<-------------|
| "reverse - M marked" M<---------------| |
|<--------------------------------M | |
| | M | |
|RESERVE(RMD-QSPEC, K=0): M | |
|"forward - T tear" M | |
|--------------->| RESERVE(RMD-QSPEC, K=0): | |
| | "forward - T tear" | |
| |-------------------------------->| |
| | M |------------->|
| | M RESERVE(RMD-QSPEC, K=0):
| | M "reverse - T tear" |
| | M |<-------------|
| M RESERVE(RMD-QSPEC, K=1) |
| | M "forward - T tear" |
| | M<---------------| |
| RESERVE(RMD-QSPEC, K=1)M | |
| "forward - T tear" M | |
|<--------------------------------M | |
Figure 19: Intra-domain signaling normal operation for unsuccessful
bidirectional reservation (rejection on path QNE(Egress)
towards QNE(Ingress)
* the QNE Ingress uses the information contained in the received PHR
and PDR containers of the RESERVE(RMD-QSPEC): "reverse" and
generates a tear intra-domain RESERVE(RMD-QSPEC): "forward - T
tear" message. This message carries a "PHR_Release_Request" and
"PDR_Release_Request" control information. This message is sent
to the QNE Egress node. The QNE Egress node uses the information
contained in the "PHR_Release_Request" and the
"PDR_Release_Request" control info containers to generate a
RESERVE(RMD-QSPEC): "reverse - T tear" message that is sent
towards the QNE Ingress node.
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4.6.2.2. Refresh Reservations
This section describes the operation of the RMD-QOSM where an RMD
intra-domain bidirectional refresh reservation operation is
accomplished.
The refresh procedure in the case of an RMD reservation-based method
follows a scheme similar to the successful reservation procedure,
described in Section 4.6.2.1 and depicted in Figure 17, and how the
refresh process of the reserved resources is maintained and is
similar to the refresh process used for the intra-domain
unidirectional reservations (see Section 4.6.1.3).
Note that the RMD traffic class refresh periods used by the bound
bidirectional sessions MUST be equal in all QNE Edge and QNE Interior
nodes.
The main differences between the RESERVE(RMD-QSPEC): "forward"
message used for the bidirectional refresh procedure and a
RESERVE(RMD-QSPEC): "forward" message used for the bidirectional
successful reservation procedure are as follows:
* the value of the Parameter ID of the PHR container is "19", i.e.,
"PHR_Refresh_Update".
* the value of the Parameter ID of the PDR container is "21", i.e.,
"PDR_Refresh_Request".
The main differences between the RESERVE(RMD-QSPEC): "reverse"
message used for the bidirectional refresh procedure and the RESERVE
(RMD-QSPEC): "reverse" message used for the bidirectional successful
reservation procedure are as follows:
* the value of the Parameter ID of the PHR container is "19", i.e.,
"PHR_Refresh_Update".
* the value of the Parameter ID of the PDR container is "24", i.e.,
"PDR_Refresh_Report".
4.6.2.3. Modification of Aggregated Intra-Domain QoS-NSLP Operational
Reservation States
This section describes the operation of the RMD-QOSM where RMD intra-
domain bidirectional QoS-NSLP aggregated reservation states have to
be modified.
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In the case when the QNE Edges maintain, for the RMD QoS Model, QoS-
NSLP aggregated reservation states and if such an aggregated
reservation has to be modified (see Section 4.3.1), then similar
procedures to Section 4.6.1.4 are applied. In particular:
* When the modification request requires an increase of the reserved
resources, the QNE Ingress node MUST include the corresponding
value into the <Peak Data Rate-1 (p)> field local RMD-QSPEC
<TMOD-1> parameter of the RMD-QOSM <QoS Desired>), which is sent
together with "PHR_Resource_Request" control information. If a
QNE Edge or QNE Interior node is not able to reserve the number of
requested resources, then the "PHR_Resource_Request" associated
with the local RMD-QSPEC <TMOD-1> parameter MUST be marked. In
this situation, the RMD-specific operation for unsuccessful
reservation will be applied (see Section 4.6.2.1). Note that the
value of the <PDR Bandwidth> parameter, which is sent within a
"PDR_Reservation_Request" container, represents the increase of
the reserved resources in the "reverse" direction.
* When the modification request requires a decrease of the reserved
resources, the QNE Ingress node MUST include this value into the
<Peak Data Rate-1 (p)> field of the local RMD-QSPEC <TMOD-1>
parameter of the RMD-QOSM <QoS Desired>). Subsequently, an RMD
release procedure SHOULD be accomplished (see Section 4.6.2.4).
Note that the value of the <PDR Bandwidth> parameter, which is
sent within a "PDR_Release_Request" container, represents the
decrease of the reserved resources in the "reverse" direction.
4.6.2.4. Release Procedure
This section describes the operation of the RMD-QOSM, where an RMD
intra-domain bidirectional reservation release operation is
accomplished. The message sequence diagram used in this procedure is
similar to the one used by the successful reservation procedures,
described in Section 4.6.2.1 and depicted in Figure 17. However, how
the release of the reservation is accomplished is similar to the RMD
release procedure used for the intra-domain unidirectional
reservations (see Section 4.6.1.5 and Figures 18 and 19).
The main differences between the RESERVE (RMD-QSPEC): "forward"
message used for the bidirectional release procedure and a RESERVE
(RMD-QSPEC): "forward" message used for the bidirectional successful
reservation procedure are as follows:
* the value of the Parameter ID of the PHR container is "18",
i.e."PHR_Release_Request";
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* the value of the Parameter ID of the PDR container is "22", i.e.,
"PDR_Release_Request";
The main differences between the RESERVE (RMD-QSPEC): "reverse"
message used for the bidirectional release procedure and the RESERVE
(RMD-QSPEC): "reverse" message used for the bidirectional successful
reservation procedure are as follows:
* the value of the Parameter ID of the PHR container is "18", i.e.,
"PHR_Release_Request";
* the PDR container is not included in the RESERVE (RMD-QSPEC):
"reverse" message.
4.6.2.5. Severe Congestion Handling
This section describes the severe congestion handling operation used
in combination with RMD intra-domain bidirectional reservation
procedures. This severe congestion handling operation is similar to
the one described in Section 4.6.1.6.
4.6.2.5.1. Severe Congestion Handling by the RMD-QOSM Bidirectional
Refresh Procedure
This procedure is similar to the severe congestion handling procedure
described in Section 4.6.1.6.1. The difference is related to how the
refresh procedure is accomplished (see Section 4.6.2.2) and how the
flows are terminated (see Section 4.6.2.4).
4.6.2.5.2. Severe Congestion Handling by Proportional Data Packet
Marking
This section describes the severe congestion handling by proportional
data packet marking when this is combined with an RMD intra-domain
bidirectional reservation procedure. Note that the detection and
marking/re-marking functionality described in this section and used
by Interior nodes, applies to NSIS-aware but also to NSIS-unaware
nodes. This means however, that the "not NSIS-aware" Interior nodes
MUST be configured such that they can detect the congestion
situations and re-mark packets in the same way as the Interior "NSIS-
aware" nodes do.
This procedure is similar to the severe congestion handling procedure
described in Section 4.6.1.6.2. The main difference is related to
the location of the severe congested node, i.e., "forward" or
"reverse" path. Note that when a severe congestion situation occurs,
e.g., on a forward path, and flows are terminated to solve the severe
congestion in forward path, then the reserved bandwidth associated
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with the terminated bidirectional flows will also be released.
Therefore, a careful selection of the flows that have to be
terminated SHOULD take place. An example of such a selection is
given in Appendix A.5.
Furthermore, a special case of this operation is associated with the
severe congestion situation occurring simultaneously on the forward
and reverse paths. An example of this operation is given in Appendix
A.6.
Simulation results associated with these procedures can be found in
[DiKa08].
QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress)
NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful
user| | | | |
data| user | | | |
--->| data | user data | |user data |
|--------------->| | S |
| |--------------------------->S (#marked bytes)
| | | S-------------->|
| | | S(#unmarked bytes)
| | | S-------------->|Term
| | | S |flow?
| | NOTIFY (PDR) S |YES
|<------------------------------------------------------------|
|RESERVE(RMD-QSPEC) | S |
|"forward - T tear" | S |
|--------------->| | RESERVE(RMD-QSPEC):|
| |--------------------------->S"forward - T tear"
| | | S-------------->|
| | | RESERVE(RMD-QSPEC): |
| | | "reverse - T tear" |
| RESERVE(RMD-QSPEC): | |<--------------|
|"reverse - T tear" |<-------------S |
|<-----------------------------| S |
Figure 20: Intra-domain RMD severe congestion handling for
bidirectional reservation (congestion on path
QNE(Ingress) towards QNE(Egress))
Figure 20 shows the scenario in which the severely congested node is
located in the "forward" path. The QNE Egress node has to generate
an end-to-end NOTIFY (PDR) message. In this way, the QNE Ingress
will be able to receive the (#marked and #unmarked) that were
measured by the QNE Egress node on the congested "forward" path.
Note that in this situation, it is assumed that the "reverse" path is
not congested.
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This scenario is very similar to the severe congestion handling
scenario described in Section 4.6.1.6.2 and shown in Figure 14. The
difference is related to the release procedure, which is accomplished
in the same way as described in Section 4.6.2.4.
Figure 21 shows the scenario in which the severely congested node is
located in the "reverse" path. Note that in this situation, it is
assumed that the "forward" path is not congested. The main
difference between this scenario and the scenario shown in Figure 20
is that no end-to-end NOTIFY (PDR) message has to be generated by the
QNE Egress node.
This is because now the severe congestion occurs on the "reverse"
path and the QNE Ingress node receives the (#marked and #unmarked)
user data passing through the severely congested "reverse" path. The
QNE Ingress node will be able to calculate the number of flows that
have to be terminated or forwarded in a lower priority queue.
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QNE(Ingress) QNE (int.) QNE (int.) QNE (int.) QNE(Egress)
NTLP stateful NTLP st.less NTLP st.less NTLP st.less NTLP stateful
user| | | | |
data| user | | | |
--->| data | user data | |user data |
|--------------->| | | |
| |--------------------------->|user data |user
| | | |-------------->|data
| | | | |--->
| | | user | |<---
| user data | | data |<--------------|
| (#marked bytes)| S<----------| |
|<--------------------------------S | |
| (#unmarked bytes) S | |
Term|<--------------------------------S | |
Flow? | S | |
YES |RESERVE(RMD-QSPEC): S | |
|"forward - T tear" s | |
|--------------->| RESERVE(RMD-QSPEC): | |
| | "forward - T tear" | |
| |--------------------------->| |
| | S |-------------->|
| | S RESERVE(RMD-QSPEC):
| | S "reverse - T tear" |
| RESERVE(RMD-QSPEC) S |<--------------|
| "reverse - T tear" S<----------| |
|<--------------------------------S | |
Figure 21: Intra-domain RMD severe congestion handling for
bidirectional reservation (congestion on path
QNE(Egress) towards QNE(Ingress))
For the flows that have to be terminated, a release procedure, see
Section 4.6.2.4, is initiated to release the reserved resources on
the "forward" and "reverse" paths.
4.6.2.6. Admission Control Using Congestion Notification Based on
Probing
This section describes the admission control scheme that uses the
congestion notification function based on probing when RMD intra-
domain bidirectional reservations are supported.
Bader, et al. Experimental [Page 87]
RFC 5977 RMD-QOSM October 2010
QNE(Ingress) Interior QNE (int.) Interior QNE(Egress)
NTLP stateful not NSIS aware not NSIS aware not NSIS aware NTLP stateful
user| | | | |
data| | | | |
--->| | user data | |user data |
|-------------------------------------------->S (#marked bytes)
| | | S-------------->|
| | | S(#unmarked bytes)
| | | S-------------->|
| | | S |
| | RESERVE(re-marked DSCP in GIST)):|
| | | S |
|-------------------------------------------->S |
| | | S-------------->|
| | | S |
| | RESPONSE(unsuccessful INFO-SPEC) |
|<------------------------------------------------------------|
| | | S |
Figure 22: Intra-domain RMD congestion notification based on
probing for bidirectional admission control (congestion
on path from QNE(Ingress) towards QNE(Egress))
This procedure is similar to the congestion notification for
admission control procedure described in Section 4.6.1.7. The main
difference is related to the location of the severe congested node,
i.e., "forward" path (i.e., path between QNE Ingress towards QNE
Egress) or "reverse" path (i.e., path between QNE Egress towards QNE
Ingress).
Figure 22 shows the scenario in which the severely congested node is
located in the "forward" path. The functionality of providing
admission control is the same as that described in Section 4.6.1.7,
Figure 15.
Figure 23 shows the scenario in which the congested node is located
in the "reverse" path. The probe RESERVE message sent in the
"forward" direction will not be affected by the severely congested
node, while the <DSCP> value in the IP header of any packet of the
"reverse" direction flow and also of the GIST message that carries
the probe RESERVE message sent in the "reverse" direction will be re-
marked by the congested node. The QNE Ingress is, in this way,
notified that a congestion occurred in the network, and therefore it
is able to refuse the new initiation of the reservation.
Bader, et al. Experimental [Page 88]
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Note that the "not NSIS-aware" Interior nodes MUST be configured such
that they can detect the congestion/severe congestion situations and
re-mark packets in the same way as the Interior "NSIS-aware" nodes
do.
QNE(Ingress) Interior QNE (int.) Interior QNE(Egress)
NTLP stateful not NSIS aware NTLP st.less not NSIS aware NTLP stateful
user| | | | |
data| | | | |
--->| | user data | | |
|-------------------------------------------->|user data |user
| | | |-------------->|data
| | | | |--->
| | | | |user
| | | | |data
| | | | |<---
| S | user data | |
| S user data |<--------------------------|
| user data S<---------------| | |
|<---------------S | | |
| user data S | | |
| (#marked bytes)S | | |
|<---------------S | | |
| S RESERVE(unmarked DSCP in GIST)): |
| S | | |
|----------------S------------------------------------------->|
| S RESERVE(re-marked DSCP in GIST) |
| S<-------------------------------------------|
|<---------------S | | |
Figure 23: Intra-domain RMD congestion notification for
bidirectional admission control (congestion on path
QNE(Egress) towards QNE(Ingress))
4.7. Handling of Additional Errors
During the QSPEC processing, additional errors MAY occur. The way in
which these additional errors are handled and notified is specified
in [RFC5975] and [RFC5974].
5. Security Considerations
5.1. Introduction
A design goal of the RMD-QOSM protocol is to be "lightweight" in
terms of the number of exchanged signaling message and the amount of
state established at involved signaling nodes (with and without
reduced-state operation). A side effect of this design decision is
Bader, et al. Experimental [Page 89]
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to introduce second-class signaling nodes, namely QNE Interior nodes,
that are restricted in their ability to perform QoS signaling
actions. Only the QNE Ingress and the QNE Egress nodes are allowed
to initiate certain signaling messages.
Moreover, RMD focuses on an intra-domain deployment only.
The above description has the following implications for security:
1) QNE Ingress and QNE Egress nodes require more security and fault
protection than QNE Interior nodes because their uncontrolled
behavior has larger implications for the overall stability of the
network. QNE Ingress and QNE Egress nodes share a security
association and utilize GIST security for protection of their
signaling messages. Intra-domain signaling messages used for RMD
signaling do not use GIST security, and therefore they do not
store security associations.
2) The focus on intra-domain QoS signaling simplifies trust
management and reduces overall complexity. See Section 2 of RFC
4081 for a more detailed discussion about the complete set of
communication models available for end-to-end QoS signaling
protocols. The security of RMD-QOSM does not depend on Interior
nodes, and hence the cryptographic protection of intra-domain
messages via GIST is not utilized.
It is important to highlight that RMD always uses the message
exchange shown in Figure 24 even if there is no end-to-end signaling
session. If the RMD-QOSM is triggered based on an end-to-end (E2E)
signaling exchange, then the RESERVE message is created by a node
outside the RMD domain and will subsequently travel further (e.g., to
the data receiver). Such an exchange is shown in Figure 3. As such,
an evaluation of an RMD's security always has to be seen as a
combination of the two signaling sessions, (1) and (2) of Figure 24.
Note that for the E2E message, such as the RESERVE and the RESPONSE
message, a single "hop" refers to the communication between the QNE
Ingress and the QNE Egress since QNE Interior nodes do not
participate in the exchange.
Bader, et al. Experimental [Page 90]
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QNE QNE QNE QNE
Ingress Interior Interior Egress
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
| RESERVE (1) | | |
+--------------------------------------------->|
| RESERVE' (2) | | |
+-------------->| | |
| | RESERVE' | |
| +-------------->| |
| | | RESERVE' |
| | +------------->|
| | | RESPONSE' (2)|
|<---------------------------------------------+
| | | RESPONSE (1) |
|<---------------------------------------------+
Figure 24: RMD message exchange
Authorizing quality-of-service reservations is accomplished using the
Authentication, Authorization, and Accounting (AAA) framework and the
functionality is inherited from the underlying NSIS QoS NSLP, see
[RFC5974], and not described again in this document. As a technical
solution mechanism, the Diameter QoS application [RFC5866] may be
used. The end-to-end reservation request arriving at the Ingress
node will trigger the authorization procedure with the backend AAA
infrastructure. The end-to-end reservation is typically triggered by
a human interaction with a software application, such as a voice-
over-IP client when making a call. When authorization is successful
then no further user initiated QoS authorization check is expected to
be performed within the RMD domain for the intra-domain reservation.
5.2. Security Threats
In the RMD-QOSM, the Ingress node constructs both end-to-end and
intra-domain signaling messages based on the end-to-end message
initiated by the sender end node.
The Interior nodes within the RMD network ignore the end-to-end
signaling message, but they process, modify, and forward the intra-
domain signaling messages towards the Egress node. In the meantime,
resource reservation states are installed, modified, or deleted at
each Interior node along the data path according to the content of
each intra-domain signaling message. The Edge nodes of an RMD
network are critical components that require strong security
protection.
Bader, et al. Experimental [Page 91]
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Therefore, they act as security gateways for incoming and outgoing
signaling messages. Moreover, a certain degree of trust has to be
placed into Interior nodes within the RMD-QOSM network, such that
these nodes can perform signaling message processing and take the
necessary actions.
With the RMD-QOSM, we assume that the Ingress and the Egress nodes
are not controlled by an adversary and the communication between the
Ingress and the Egress nodes is secured using standard GIST security,
(see Section 6 of [RFC5971]) mechanisms and experiences integrity,
replay, and confidentiality protection.
Note that this only affects messages directly addressed by these two
nodes and not any other message that needs to be processed by
intermediaries. The <SESSION-ID> object of the end-to-end
communication is visible, via GIST, to the Interior nodes. In order
to define the security threats that are associated with the RMD-QOSM,
we consider that an adversary that may be located inside the RMD
domain and could drop, delay, duplicate, inject, or modify signaling
packets.
Depending on the location of the adversary, we speak about an on-path
adversary or an off-path adversary, see also RFC 4081 [RFC4081].
5.2.1. On-Path Adversary
The on-path adversary is a node, which supports RMD-QOSM and is able
to observe RMD-QOSM signaling message exchanges.
1) Dropping signaling messages
An adversary could drop any signaling messages after receiving them.
This will cause a failure of reservation request for new sessions or
deletion of resource units (bandwidth) for ongoing sessions due to
states timeout.
It may trigger the Ingress node to retransmit the lost signaling
messages. In this scenario, the adversary drops selected signaling
messages, for example, intra-domain reserve messages. In the RMD-
QOSM, the retransmission mechanism can be provided at the Ingress
node to make sure that signaling messages can reach the Egress node.
However, the retransmissions triggered by the adversary dropping
messages may cause certain problems. Therefore, disabling the use of
retransmissions in the RMD-QOSM-aware network is recommended, see
also Section 4.6.1.1.1.
Bader, et al. Experimental [Page 92]
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2) Delaying Signaling Messages
Any signaling message could be delayed by an adversary. For example,
if RESERVE' messages are delayed over the duration of the refresh
period, then the resource units (bandwidth) reserved along the nodes
for corresponding sessions will be removed. In this situation, the
Ingress node does not receive the RESPONSE within a certain period,
and considers that the signaling message has failed, which may cause
a retransmission of the "failed" message. The Egress node may
distinguish between the two messages, i.e., the delayed message and
the retransmitted message, and it could get a proper response.
However, Interior nodes suffer from this retransmission and they may
reserve twice the resource units (bandwidth) requested by the Ingress
node.
3) Replaying Signaling Messages
An adversary may want to replay signaling messages. It first stores
the received messages and decides when to replay these messages and
at what rate (packets per second).
When the RESERVE' message carried an <RII> object, the Egress will
reply with a RESPONSE' message towards the Ingress node. The Ingress
node can then detect replays by comparing the value of <RII> in the
RESPONSE' messages with the stored value.
4) Injecting Signaling Messages
Similar to the replay-attack scenario, the adversary may store a part
of the information carried by signaling messages, for example, the
<RSN> object. When the adversary injects signaling messages, it puts
the stored information together with its own generated parameters
(RMD-QSPEC <TMOD-1> parameter, <RII>, etc.) into the injected
messages and then sends them out. Interior nodes will process these
messages by default, reserve the requested resource units (bandwidth)
and pass them to downstream nodes.
It may happen that the resource units (bandwidth) on the Interior
nodes are exhausted if these injected messages consume too much
bandwidth.
5) Modifying Signaling Messages
On-path adversaries are capable of modifying any part of the
signaling message. For example, the adversary can modify the <M>,
<S>, and <O> parameters of the RMD-QSPEC messages. The Egress node
will then use the SESSION-ID and subsequently the <BOUND-SESSION-ID>
Bader, et al. Experimental [Page 93]
RFC 5977 RMD-QOSM October 2010
objects to refer to that flow to be terminated or set to lower
priority. It is also possible for the adversary to modify the RMD-
QSPEC <TMOD-1> parameter and/or <PHB Class> parameter, which could
cause a modification of an amount of the requested resource units
(bandwidth) changes.
5.2.2. Off-Path Adversary
In this case, the adversary is not located on-path and it does not
participate in the exchange of RMD-QOSM signaling messages, and
therefore is unable to eavesdrop signaling messages. Hence, the
adversary does not know valid <RII>s, <RSN>s, and <SESSION-ID>s.
Hence, the adversary has to generate new parameters and constructs
new signaling messages. Since Interior nodes operate in reduced-
state mode, injected signaling messages are treated as new once,
which causes Interior nodes to allocate additional reservation state.
5.3. Security Requirements
The following security requirements are set as goals for the intra-
domain communication, namely:
* Nodes, which are never supposed to participate in the NSIS
signaling exchange, must not interfere with QNE Interior nodes.
Off-path nodes (off-path with regard to the path taken by a
particular signaling message exchange) must not be able to
interfere with other on-path signaling nodes.
* The actions allowed by a QNE Interior node should be minimal
(i.e., only those specified by the RMD-QOSM). For example, only
the QNE Ingress and the QNE Egress nodes are allowed to initiate
certain signaling messages. QNE Interior nodes are, for example,
allowed to modify certain signaling message payloads.
Note that the term "interfere" refers to all sorts of security
threats, such as denial-of-service, spoofing, replay, signaling
message injection, etc.
5.4. Security Mechanisms
An important security mechanism that was built into RMD-QOSM was the
ability to tie the end-to-end RESERVE and the RESERVE' messages
together using the BOUND-SESSION-ID and to allow the Ingress node to
match the RESERVE' with the RESPONSE' by using the <RII>. These
mechanisms enable the Edge nodes to detect unexpected signaling
messages.
Bader, et al. Experimental [Page 94]
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We assume that the RESERVE/RESPONSE is sent with hop-by-hop channel
security provided by GIST and protected between the QNE Ingress and
the QNE Egress. GIST security mechanisms MUST be used to offer
authentication, integrity, and replay protection. Furthermore,
encryption MUST be used to prevent an adversary located along the
path of the RESERVE message from learning information about the
session that can later be used to inject a RESERVE' message.
The following messages need to be mapped to each other to make sure
that the occurrence of one message is not without the other:
a) the RESERVE and the RESERVE' relate to each other at the QNE
Egress; and
b) the RESPONSE and the RESERVE relate to each other at the QNE
Ingress; and
c) the RESERVE' and the RESPONSE' relate to each other. The <RII> is
carried in the RESERVE' message and the RESPONSE' message that is
generated by the QNE Egress node contains the same <RII> as the
RESERVE'. The <RII> can be used by the QNE Ingress to match the
RESERVE' with the RESPONSE'. The QNE Egress is able to determine
whether the RESERVE' was created by the QNE Ingress node since the
intra-domain session, which sent the RESERVE', is bound to an end-
to-end session via the <BOUND-SESSION-ID> value included in the
intra-domain QoS-NSLP operational state maintained at the QNE
Egress.
The RESERVE and the RESERVE' message are tied together using the
BOUND-SESSION-ID(s) maintained by the intra-domain and end-to-end
QoS-NSLP operational states maintained at the QNE Edges (see Sections
4.3.1, 4.3.2, and 4.3.3). Hence, there cannot be a RESERVE' without
a corresponding RESERVE. The SESSION-ID can fulfill this purpose
quite well if the aim is to provide protection against off-path
adversaries that do not see the SESSION-ID carried in the RESERVE and
the RESERVE' messages.
If, however, the path changes (due to rerouting or due to mobility),
then an adversary could inject RESERVE' messages (with a previously
seen SESSION-ID) and could potentially cause harm.
An off-path adversary can, of course, create RESERVE' messages that
cause intermediate nodes to create some state (and cause other
actions) but the message would finally hit the QNE Egress node. The
QNE Egress node would then be able to determine that there is
something going wrong and generate an error message.
Bader, et al. Experimental [Page 95]
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The severe congestion handling can be triggered by intermediate nodes
(unlike other messages). In many cases, however, intermediate nodes
experiencing congestion use refresh messages modify the <S> and <O>
parameters of the message. These messages are still initiated by the
QNE Ingress node and carry the SESSION-ID. The QNE Egress node will
use the SESSION-ID and subsequently the BOUND-SESSION-ID, maintained
by the intra-domain QoS-NSLP operational state, to refer to a flow
that might be terminated. The aspect of intermediate nodes
initiating messages for severe congestion handling is for further
study.
During the refresh procedure, a RESERVE' creates a RESPONSE', see
Figure 25. The <RII> is carried in the RESERVE' message and the
RESPONSE' message that is generated by the QNE Egress node contains
the same <RII> as the RESERVE'.
The <RII> can be used by the QNE Ingress to match the RESERVE' with
the RESPONSE'.
A further aspect is marking of data traffic. Data packets can be
modified by an intermediary without any relationship to a signaling
session (and a SESSION-ID). The problem appears if an off-path
adversary injects spoofed data packets.
QNE Ingress QNE Interior QNE Interior QNE Egress
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
| REFRESH RESERVE' | |
+-------------->| REFRESH RESERVE' |
| (+RII) +-------------->| REFRESH RESERVE'
| | (+RII) +------------->|
| | | (+RII) |
| | | |
| | | REFRESH |
| | | RESPONSE'|
|<---------------------------------------------+
| | | (+RII) |
Figure 25: RMD REFRESH message exchange
The adversary thereby needs to spoof data packets that relate to the
flow identifier of an existing end-to-end reservation that SHOULD be
terminated. Therefore, the question arises how an off-path adversary
SHOULD create a data packet that matches an existing flow identifier
(if a 5-tuple is used). Hence, this might not turn out to be simple
for an adversary unless we assume the previously mentioned
mobility/rerouting case where the path through the network changes
and the set of nodes that are along a path changes over time.
Bader, et al. Experimental [Page 96]
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6. IANA Considerations
This section defines additional codepoint assignments in the QSPEC
Parameter ID registry, in accordance with BCP 26 [RFC5226].
6.1. Assignment of QSPEC Parameter IDs
This document specifies the following QSPEC containers in the QSPEC
Parameter ID registry created in [RFC5975]:
<PHR_Resource_Request> (Section 4.1.2 above, ID=17)
<PHR_Release_Request> (Section 4.1.2 above, ID=18)
<PHR_Refresh_Update> (Section 4.1.2 above, ID=19)
<PDR_Reservation_Request> (Section 4.1.3 above, ID=20)
<PDR_Refresh_Request> (Section 4.1.3 above, ID=21)
<PDR_Release_Request> (Section 4.1.3 above, ID=22)
<PDR_Reservation_Report> (Section 4.1.3 above, ID=23)
<PDR_Refresh_Report> (Section 4.1.3 above, ID=24)
<PDR_Release_Report> (Section 4.1.3 above, ID=25)
<PDR_Congestion_Report> (Section 4.1.3 above, ID=26)
7. Acknowledgments
The authors express their acknowledgement to people who have worked
on the RMD concept: Z. Turanyi, R. Szabo, G. Pongracz, A. Marquetant,
O. Pop, V. Rexhepi, G. Heijenk, D. Partain, M. Jacobsson, S.
Oosthoek, P. Wallentin, P. Goering, A. Stienstra, M. de Kogel, M.
Zoumaro-Djayoon, M. Swanink, R. Klaver G. Stokkink, J. W. van
Houwelingen, D. Dimitrova, T. Sealy, H. Chang, and J. de Waal.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2983] Black, D., "Differentiated Services and Tunnels", RFC
2983, October 2000.
Bader, et al. Experimental [Page 97]
RFC 5977 RMD-QOSM October 2010
[RFC5971] Schulzrinne, H. and R. Hancock, "GIST: General Internet
Signaling Transport", RFC 5971, October 2010.
[RFC5974] Manner, J., Karagiannis, G., and A. McDonald, "NSIS
Signaling Layer Protocol (NSLP) for Quality-of-Service
Signaling", RFC 5974, October 2010.
[RFC5975] Ash, G., Bader, A., Kappler C., and D. Oran, "QSPEC
Template for the Quality-of-Service NSIS Signaling Layer
Protocol (NSLP)", RFC 5975, October 2010.
8.2. Informative References
[AdCa03] Adler, M., Cai, J.-Y., Shapiro, J. K., Towsley, D.,
"Estimation of congestion price using probabilistic packet
marking", Proc. IEEE INFOCOM, pp. 2068-2078, 2003.
[AnHa06] Lachlan L. H. Andrew and Stephen V. Hanly, "The Estimation
Error of Adaptive Deterministic Packet Marking", 44th
Annual Allerton Conference on Communication, Control and
Computing, 2006.
[AtLi01] Athuraliya, S., Li, V. H., Low, S. H., Yin, Q., "REM:
active queue management", IEEE Network, vol. 15, pp.
48-53, May/June 2001.
[Chan07] H. Chang, "Security support in RMD-QOSM", Masters thesis,
University of Twente, 2007.
[CsTa05] Csaszar, A., Takacs, A., Szabo, R., Henk, T., "Resilient
Reduced-State Resource Reservation", Journal of
Communication and Networks, Vol. 7, No. 4, December 2005.
[DiKa08] Dimitrova, D., Karagiannis, G., de Boer, P.-T., "Severe
congestion handling approaches in NSIS RMD domains with
bi-directional reservations", Journal of Computer
Communications, Elsevier, vol. 31, pp. 3153-3162, 2008.
[JaSh97] Jamin, S., Shenker, S., Danzig, P., "Comparison of
Measurement-based Admission Control Algorithms for
Controlled-Load Service", Proceedings IEEE Infocom '97,
Kobe, Japan, April 1997.
[GrTs03] Grossglauser, M., Tse, D.N.C, "A Time-Scale Decomposition
Approach to Measurement-Based Admission Control",
IEEE/ACM Transactions on Networking, Vol. 11, No. 4,
August 2003.
Bader, et al. Experimental [Page 98]
RFC 5977 RMD-QOSM October 2010
[Part94] C. Partridge, Gigabit Networking, Addison Wesley
Publishers (1994).
[RFC1633] Braden, R., Clark, D., and S. Shenker, "Integrated
Services in the Internet Architecture: an Overview", RFC
1633, June 1994.
[RFC2215] Shenker, S. and J. Wroclawski, "General Characterization
Parameters for Integrated Service Network Elements", RFC
2215, September 1997.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Service", RFC 2475, December 1998.
[RFC2638] Nichols, K., Jacobson, V., and L. Zhang, "A Two-bit
Differentiated Services Architecture for the Internet",
RFC 2638, July 1999.
[RFC2998] Bernet, Y., Ford, P., Yavatkar, R., Baker, F., Zhang, L.,
Speer, M., Braden, R., Davie, B., Wroclawski, J., and E.
Felstaine, "A Framework for Integrated Services Operation
over Diffserv Networks", RFC 2998, November 2000.
[RFC3175] Baker, F., Iturralde, C., Le Faucheur, F., and B. Davie,
"Aggregation of RSVP for IPv4 and IPv6 Reservations", RFC
3175, September 2001.
[RFC3726] Brunner, M., Ed., "Requirements for Signaling Protocols",
RFC 3726, April 2004.
[RFC4125] Le Faucheur, F. and W. Lai, "Maximum Allocation Bandwidth
Constraints Model for Diffserv-aware MPLS Traffic
Engineering", RFC 4125, June 2005.
[RFC4127] Le Faucheur, F., Ed., "Russian Dolls Bandwidth Constraints
Model for Diffserv-aware MPLS Traffic Engineering", RFC
4127, June 2005.
[RFC4081] Tschofenig, H. and D. Kroeselberg, "Security Threats for
Next Steps in Signaling (NSIS)", RFC 4081, June 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
Bader, et al. Experimental [Page 99]
RFC 5977 RMD-QOSM October 2010
[RFC5866] Sun, D., Ed., McCann, P., Tschofenig, H., Tsou, T., Doria,
A., and G. Zorn, Ed., "Diameter Quality-of-Service
Application", RFC 5866, May 2010.
[RFC5978] Manner, J., Bless, R., Loughney, J., and E. Davies, Ed.,
"Using and Extending the NSIS Protocol Family", RFC 5978,
October 2010.
[RMD1] Westberg, L., et al., "Resource Management in Diffserv
(RMD): A Functionality and Performance Behavior Overview",
IFIP PfHSN 2002.
[RMD2] G. Karagiannis, et al., "RMD - a lightweight application
of NSIS" Networks 2004, Vienna, Austria.
[RMD3] Marquetant A., Pop O., Szabo R., Dinnyes G., Turanyi Z.,
"Novel Enhancements to Load Control - A Soft-State,
Lightweight Admission Control Protocol", Proc. of the 2nd
Int. Workshop on Quality of Future Internet Services,
Coimbra, Portugal, Sept 24-26, 2001, pp. 82-96.
[RMD4] A. Csaszar et al., "Severe congestion handling with
resource management in diffserv on demand", Networking
2002.
[TaCh99] P. P. Tang, T-Y Charles Tai, "Network Traffic
Characterization Using Token Bucket Model", IEEE Infocom
1999, The Conference on Computer Communications, no. 1,
March 1999, pp. 51-62.
[ThCo04] Thommes, R. W., Coates, M. J., "Deterministic packet
marking for congestion packet estimation" Proc. IEEE
Infocom, 2004.
Bader, et al. Experimental [Page 100]
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Appendix A. Examples
A.1. Example of a Re-Marking Operation during Severe Congestion in the
Interior Nodes
This appendix describes an example of a re-marking operation during
severe congestion in the Interior nodes.
Per supported PHB, the Interior node can support the operation states
depicted in Figure 26, when the per-flow congestion notification
based on probing signaling scheme is used in combination with this
severe congestion type. Figure 27 depicts the same functionality
when the per-flow congestion notification based on probing scheme is
not used in combination with the severe congestion scheme. The
description given in this and the following appendices, focuses on
the situation where: (1) the "notified DSCP" marking is used in
congestion notification state, and (2) the "encoded DSCP" and
"affected DSCP" markings are used in severe congestion state. In
this case, the "notified DSCP" marking is used during the congestion
notification state to mark all packets passing through an Interior
node that operates in the congestion notification state. In this
way, and in combination with probing, a flow-based ECMP solution can
be provided for the congestion notification state. The "encoded
DSCP" marking is used to encode and signal the excess rate, measured
at Interior nodes, to the Egress nodes. The "affected DSCP" marking
is used to mark all packets that are passing through a severe
congested node and are not "encoded DSCP" marked.
Another possible situation could be derived in which both congestion
notification and severe congestion state use the "encoded DSCP"
marking, without using the "notified DSCP" marking. The "affected
DSCP" marking is used to mark all packets that pass through an
Interior node that is in severe congestion state and are not "encoded
DSCP" marked. In addition, the probe packet that is carried by an
intra-domain RESERVE message and pass through Interior nodes SHOULD
be "encoded DSCP" marked if the Interior node is in congestion
notification or severe congestion states. Otherwise, the probe
packet will remain unmarked. In this way, an ECMP solution can be
provided for both congestion notification and severe congestion
states. The"encoded DSCP" packets signal an excess rate that is not
only associated with Interior nodes that are in severe congestion
state, but also with Interior nodes that are in congestion
notification state. The algorithm at the Interior node is similar to
the algorithm described in the following appendix sections. However,
this method is not described in detail in this example.
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---------------------------------------------
| event B |
| V
---------- ------------- ----------
| Normal | event A | Congestion | event B | Severe |
| state |---------->| notification|-------->|congestion|
| | | state | | state |
---------- ------------- ----------
^ ^ | |
| | event C | |
| ----------------------- |
| event D |
------------------------------------------------
Figure 26: States of operation, severe congestion combined with
congestion notification based on probing
---------- -------------
| Normal | event B | Severe |
| state |-------------->| congestion |
| | | state |
---------- -------------
^ |
| event E |
---------------------------
Figure 27: States of operation, severe congestion without
congestion notification based on probing
The terms used in Figures 26 and 27 are:
Normal state: represents the normal operation conditions of the node,
i.e., no congestion.
Severe congestion state: represents the state in which the Interior
node is severely congested related to a certain PHB. It is important
to emphasize that one of the targets of the severe congestion state
solution to change the severe congestion state behavior directly to
the normal state.
Congestion notification: state in which the load is relatively high,
close to the level when congestion can occur.
event A: this event occurs when the incoming PHB rate is higher than
the "congestion notification detection" threshold and lower than the
"severe congestion detection". This threshold is used by the
congestion notification based on probing scheme, see Sections 4.6.1.7
and 4.6.2.6.
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event B: this event occurs when the incoming PHB rate is higher than
the "severe congestion detection" threshold.
event C: this event occurs when the incoming PHB rate is lower than
or equal to the "congestion notification detection" threshold.
event D: this event occurs when the incoming PHB rate is lower than
or equal to the "severe_congestion_restoration" threshold. It is
important to emphasize that this even supports one of the targets of
the severe congestion state solution to change the severe congestion
state behavior directly to the normal state.
event E: this event occurs when the incoming PHB rate is lower than
or equal to the "severe congestion restoration" threshold.
Note that the "severe congestion detection", "severe congestion
restoration" and admission thresholds SHOULD be higher than the
"congestion notification detection" threshold, i.e., "severe
congestion detection" > "congestion notification detection" and
"severe congestion restoration" > "congestion notification
detection".
Furthermore, the "severe congestion detection" threshold SHOULD be
higher than or equal to the admission threshold that is used by the
reservation-based and NSIS measurement-based signaling schemes.
"severe congestion detection" >= admission threshold.
Moreover, the "severe congestion restoration" threshold SHOULD be
lower than or equal to the "severe congestion detection" threshold
that is used by the reservation-based and NSIS measurement-based
signaling schemes, that is:
"severe congestion restoration" <= "severe congestion detection"
During severe congestion, the Interior node calculates, per traffic
class (PHB), the incoming rate that is above the "severe congestion
restoration" threshold, denoted as signaled_overload_rate, in the
following way:
* A severe congested Interior node SHOULD take into account that
packets might be dropped. Therefore, before queuing and
eventually dropping packets, the Interior node SHOULD count the
total number of unmarked and re-marked bytes received by the
severe congested node, denote this number as total_received_bytes.
Note that there are situations in which more than one Interior
node in the same path become severely congested. Therefore, any
Interior node located behind a severely congested node MAY receive
marked bytes.
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When the "severe congestion detection" threshold per PHB is set equal
to the maximum capacity allocated to one PHB used by the RMD-QOSM, it
means that if the maximum capacity associated to a PHB is fully
utilized and a packet belonging to this PHB arrives, then it is
assumed that the Interior node will not forward this packet
downstream.
In other words, this packet will either be dropped or set to another
PHB. Furthermore, this also means that after the severe congestion
situation is solved, then the ongoing flows will be able to send
their associated packets up to a total rate equal to the maximum
capacity associated with the PHB. Therefore, when more than one
Interior node located on the same path will be severely congested and
when the Interior node receives "encoded DSCP" marked packets, it
means that an Interior node located upstream is also severely
congested.
When the "severe congestion detection" threshold per PHB is set equal
to the maximum capacity allocated to one PHB, then this Interior node
MUST forward the "encoded DSCP" marked packets and it SHOULD NOT
consider these packets during its local re-marking process. In other
words, the Egress should see the excess rates encoded by the
different severely congested Interior nodes as independent, and
therefore, these independent excess rates will be added.
When the "severe congestion detection" threshold per PHB is not set
equal to the maximum capacity allocated to one PHB, this means that
after the severe congestion situation is solved, the ongoing flows
will not be able to send their associated packets up to a total rate
equal to the maximum capacity associated with the PHB, but only up to
the "severe_congestion_threshold". When more than one Interior node
located on the same communication path is severely congested and when
one of these Interior node receives "encoded_DSCP" marked packets,
this Interior node SHOULD NOT mark unmarked, i.e., either "original
DSCP" or "affected DSCP" or "notified DSCP" encoded packets, up to a
rate equal to the difference between the maximum PHB capacity and the
"severe congestion threshold", when the incoming "encoded DSCP"
marked packets are already able to signal this difference. In this
case, the "severe congestion threshold" SHOULD be configured in all
Interior nodes, which are located in the RMD domain, and equal to:
"severe_congestion_threshold" =
Maximum PHB capacity - threshold_offset_rate
The threshold_offset_rate represents rate and SHOULD have the same
value in all Interior nodes.
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* before queuing and eventually dropping the packets, at the end of
each measurement interval of T seconds, calculate the current
estimated overloaded rate, say measured_overload_rate, by using
the following equation:
measured_overload_rate =
=((total_received_bytes)/T)-severe_congestion_restoration)
To provide a reliable estimation of the encoded information, several
techniques can be used; see [AtLi01], [AdCa03], [ThCo04], and
[AnHa06]. Note that since marking is done in Interior nodes, the
decisions are made at Egress nodes, and the termination of flows is
performed by Ingress nodes, there is a significant delay until the
overload information is learned by the Ingress nodes (see Section 6
of [CsTa05]). The delay consists of the trip time of data packets
from the severely congested Interior node to the Egress, the
measurement interval, i.e., T, and the trip time of the notification
signaling messages from Egress to Ingress. Moreover, until the
overload decreases at the severely congested Interior node, an
additional trip time from the Ingress node to the severely congested
Interior node MUST expire. This is because immediately before
receiving the congestion notification, the Ingress MAY have sent out
packets in the flows that were selected for termination. That is, a
terminated flow MAY contribute to congestion for a time longer that
is taken from the Ingress to the Interior node. Without considering
the above, Interior nodes would continue marking the packets until
the measured utilization falls below the severe congestion
restoration threshold. In this way, in the end, more flows will be
terminated than necessary, i.e., an overreaction takes place.
[CsTa05] provides a solution to this problem, where the Interior
nodes use a sliding window memory to keep track of the signaling
overload in a couple of previous measurement intervals. At the end
of a measurement interval, T, before encoding and signaling the
overloaded rate as "encoded DSCP" packets, the actual overload is
decreased with the sum of already signaled overload stored in the
sliding window memory, since that overload is already being handled
in the severe congestion handling control loop. The sliding window
memory consists of an integer number of cells, i.e., n = maximum
number of cells. Guidelines for configuring the sliding window
parameters are given in [CsTa05].
At the end of each measurement interval, the newest calculated
overload is pushed into the memory, and the oldest cell is dropped.
If Mi is the overload_rate stored in ith memory cell (i = [1..n]),
then at the end of every measurement interval, the overload rate that
is signaled to the Egress node, i.e., signaled_overload_rate is
calculated as follows:
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Sum_Mi =0
For i =1 to n
{
Sum_Mi = Sum_Mi + Mi
}
signaled_overload_rate = measured_overload_rate - Sum_Mi,
where Sum_Mi is calculated as above.
Next, the sliding memory is updated as follows:
for i = 1..(n-1): Mi <- Mi+1
Mn <- signaled_overload_rate
The bytes that have to be re-marked to satisfy the signaled overload
rate: signaled_remarked_bytes, are calculated using the following
pseudocode:
IF severe_congestion_threshold <> Maximum PHB capacity
THEN
{
IF (incoming_encoded-DSCP_rate <> 0) AND
(incoming_encoded-DSCP_rate =< termination_offset_rate)
THEN
{ signaled_remarked_bytes =
= ((signaled_overload_rate - incoming_encoded-DSCP_rate)*T)/N
}
ELSE IF (incoming_encoded-DSCP_rate > termination_offset_rate)
THEN signaled_remarked_bytes =
= ((signaled_overload_rate - termination_offset_rate)*T)/N
ELSE IF (incoming_encoded-DSCP_rate =0)
THEN signaled_remarked_bytes =
= signaled_overload_rate*T/N
}
ELSE signaled_remarked_bytes = signaled_overload_rate *T/N
Where the incoming "encoded DSCP" rate is calculated as follows:
incoming_encoded-DSCP_rate =
= (received number of "encoded_DSCP" during T) * N)/T;
The signal_remarked_bytes also represents the number of the outgoing
packets (after the dropping stage) that MUST be re-marked, during
each measurement interval T, by a node when operates in severe
congestion mode.
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Note that, in order to process an overload situation higher than 100%
of the maintained severe congestion threshold, all the nodes within
the domain MUST be configured and maintain a scaling parameter, e.g.,
N used in the above equation, which in combination with the marked
bytes, e.g., signaled_remarked_bytes, such a high overload situation
can be calculated and represented. N can be equal to or higher than
1.
Note that when incoming re-marked bytes are dropped, the operation of
the severe congestion algorithm MAY be affected, e.g., the algorithm
MAY become, in certain situations, slower. An implementation of the
algorithm MAY assure as much as possible that the incoming marked
bytes are not dropped. This could for example be accomplished by
using different dropping rate thresholds for marked and unmarked
bytes.
Note that when the "affected DSCP" marking is used by a node that is
congested due to a severe congestion situation, then all the outgoing
packets that are not marked (i.e., by using the "encoded DSCP") have
to be re-marked using the "affected DSCP" marking.
The "encoded DSCP" and the "affected DSCP" marked packets (when
applied in the whole RMD domain) are propagated to the QNE Edge
nodes.
Furthermore, note that when the congestion notification based on
probing is used in combination with severe congestion, then in
addition to the possible "encoded DSCP" and "affected DSCP", another
DSCP for the re-marking of the same PHB is used (see Section
4.6.1.7). This additional DSCP is denoted in this document as
"notified DSCP". When an Interior node operates in the severe
congested state (see Figure 27), and receives "notified DSCP"
packets, these packets are considered to be unmarked packets (but not
"affected DSCP" packets). This means that during severe congestion,
also the "notified DSCP" packets can be re-marked and encoded as
either "encoded DSCP" or "affected DSCP" packets.
A.2. Example of a Detailed Severe Congestion Operation in the Egress
Nodes
This appendix describes an example of a detailed severe congestion
operation in the Egress nodes.
The states of operation in Egress nodes are similar to the ones
described in Appendix A.1. The definition of the events, see below,
is however different than the definition of the events given in
Figures 26 and 27:
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* event A: when the Egress receives a predefined rate of "notified
DSCP" marked bytes/packets, event A is activated (see Sections
4.6.1.7 and A.4). The predefined rate of "notified DSCP" marked
bytes is denoted as the congestion notification detection
threshold. Note this congestion notification detection threshold
can also be zero, meaning that the event A is activated when the
Egress node, during an interval T, receives at least one "notified
DSCP" packet.
* event B: this event occurs when the Egress receives packets marked
as either "encoded DSCP" or "affected DSCP" (when "affected DSCP"
is applied in the whole RMD domain).
* event C: this event occurs when the rate of incoming "notified
DSCP" packets decreases below the congestion notification
detection threshold. In the situation that the congestion
notification detection threshold is zero, this will mean that
event C is activated when the Egress node, during an interval T,
does not receive any "notified DSCP" marked packets.
* event D: this event occurs when the Egress, during an interval T,
does not receive packets marked as either "encoded DSCP" or
"affected DSCP" (when "affected DSCP" is applied in the whole RMD
domain). Note that when "notified DSCP" is applied in the whole
RMD domain for the support of congestion notification, this event
could cause the following change in operation state.
When the Egress, during an interval T, does not receive (1)
packets marked as either "encoded DSCP" or "affected DSCP" (when
"affected DSCP" is applied in the whole RMD domain) and (2) it
does NOT receive "notified DSCP" marked packets, the change in the
operation state occurs from the severe congestion state to normal
state.
When the Egress, during an interval T, does not receive (1)
packets marked as either "encoded DSCP" or "affected DSCP" (when
"affected DSCP" is applied in the whole RMD domain) and (2) it
does receive "notified DSCP" marked packets, the change in the
operation state occurs from the severe congestion state to the
congestion notification state.
* event E: this event occurs when the Egress, during an interval T,
does not receive packets marked as either "encoded DSCP" or
"affected DSCP" (when "affected DSCP" is applied in the whole RMD
domain).
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An example of the algorithm for calculation of the number of flows
associated with each priority class that have to be terminated is
explained by the pseudocode below.
The Edge nodes are able to support severe congestion handling by: (1)
identifying which flows were affected by the severe congestion and
(2) selecting and terminating some of these flows such that the
quality of service of the remaining flows is recovered.
The "encoded DSCP" and the "affected DSCP" marked packets (when
applied in the whole RMD domain) are received by the QNE Edge node.
The QNE Edge nodes keep per-flow state and therefore they can
translate the calculated bandwidth to be terminated, to number of
flows. The QNE Egress node records the excess rate and the identity
of all the flows, arriving at the QNE Egress node, with "encoded
DSCP" and with "affected DSCP" (when applied in the whole RMD
domain); only these flows, which are the ones passing through the
severely congested Interior node(s), are candidates for termination.
The excess rate is calculated by measuring the rate of all the
"encoded DSCP" data packets that arrive at the QNE Egress node. The
measured excess rate is converted by the Egress node, by multiplying
it by the factor N, which was used by the QNE Interior node(s) to
encode the overload level.
When different priority flows are supported, all the low priority
flows that arrived at the Egress node are terminated first. Next,
all the medium priority flows are stopped and finally, if necessary,
even high priority flows are chosen. Within a priority class both
"encoded DSCP" and "affected DSCP" are considered before the
mechanism moves to higher priority class. Finally, for each flow
that has to be terminated the Egress node, sends a NOTIFY message to
the Ingress node, which stops the flow.
Below, this algorithm is described in detail.
First, when the Egress operates in the severe congestion state, the
total amount of re-marked bandwidth associated with the PHB traffic
class, say total_congested_bandwidth, is calculated. Note that when
the node maintains information about each Ingress/Egress pair
aggregate, then the total_congested_bandwidth MUST be calculated per
Ingress/Egress pair reservation aggregate. This bandwidth represents
the severely congested bandwidth that SHOULD be terminated. The
total_congested_bandwidth can be calculated as follows:
total_congested_bandwidth = N*input_remarked_bytes/T
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Where, input_remarked_bytes represents the number of "encoded DSCP"
marked bytes that arrive at the Egress, during one measurement
interval T, N is defined as in Sections 4.6.1.6.2.1 and A.1. The
term denoted as terminated_bandwidth is a temporal variable
representing the total bandwidth that has to be terminated, belonging
to the same PHB traffic class. The terminate_flow_bandwidth
(priority_class) is the total bandwidth associated with flows of
priority class equal to priority_class. The parameter priority_class
is an integer fulfilling:
0 =< priority_class =< Maximum_priority.
The QNE Egress node records the identity of the QNE Ingress node that
forwarded each flow, the total_congested_bandwidth and the identity
of all the flows, arriving at the QNE Egress node, with "encoded
DSCP" and "affected DSCP" (when applied in whole RMD domain). This
ensures that only these flows, which are the ones passing through the
severely overloaded QNE Interior node(s), are candidates for
termination. The selection of the flows to be terminated is
described in the pseudocode that is given below, which is realized by
the function denoted below as calculate_terminate_flows().
The calculate_terminate_flows() function uses the
<terminate_bandwidth_class> value and translates this bandwidth value
to number of flows that have to be terminated. Only the "encoded
DSCP" flows and "affected DSCP" (when applied in whole RMD domain)
flows, which are the ones passing through the severely overloaded
Interior node(s), are candidates for termination.
After the flows to be terminated are selected, the
<sum_bandwidth_terminate(priority_class)> value is calculated that is
the sum of the bandwidth associated with the flows, belonging to a
certain priority class, which will certainly be terminated.
The constraint of finding the total number of flows that have to be
terminated is that sum_bandwidth_terminate(priority_class), SHOULD be
smaller or approximately equal to the variable
terminate_bandwidth(priority_class).
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terminated_bandwidth = 0;
priority_class = 0;
while terminated_bandwidth < total_congested_bandwidth
{
terminate_bandwidth(priority_class) =
= total_congested_bandwidth - terminated_bandwidth
calculate_terminate_flows(priority_class);
terminated_bandwidth =
= sum_bandwidth_terminate(priority_class) + terminated_bandwidth;
priority_class = priority_class + 1;
}
If the Egress node maintains Ingress/Egress pair reservation
aggregates, then the above algorithm is performed for each
Ingress/Egress pair reservation aggregate.
Finally, for each flow that has to be terminated, the QNE Egress node
sends a NOTIFY message to the QNE Ingress node to terminate the flow.
A.3. Example of a Detailed Re-Marking Admission Control (Congestion
Notification) Operation in Interior Nodes
This appendix describes an example of a detailed re-marking admission
control (congestion notification) operation in Interior nodes. The
predefined congestion notification threshold, see Appendix A.1, is
set according to, and usually less than, an engineered bandwidth
limitation, i.e., admission threshold, e.g., based on a Service Level
Agreement or a capacity limitation of specific links.
The difference between the congestion notification threshold and the
engineered bandwidth limitation, i.e., admission threshold, provides
an interval where the signaling information on resource limitation is
already sent by a node but the actual resource limitation is not
reached. This is due to the fact that data packets associated with
an admitted session have not yet arrived, which allows the admission
control process available at the Egress to interpret the signaling
information and reject new calls before reaching congestion.
Note that in the situation when the data rate is higher than the
preconfigured congestion notification rate, data packets are also re-
marked (see Section 4.6.1.6.2.1). To distinguish between congestion
notification and severe congestion, two methods MAY be used (see
Appendix A.1):
* using different <DSCP> values (re-marked <DSCP> values). The re-
marked DSCP that is used for this purpose is denoted as "notified
DSCP" in this document. When this method is used and when the
Interior node is in "congestion notification" state, see Appendix
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A.1, then the node SHOULD re-mark all the unmarked bytes passing
through the node using the "notified DSCP". Note that this method
can only be applied if all nodes in the RMD domain use the
"notified" DSCP marking. In this way, probe packets that will
pass through the Interior node that operates in congestion
notification state are also encoded using the "notified DSCP"
marking.
* Using the "encoded DSCP" marking for congestion notification and
severe congestion. This method is not described in detail in this
example appendix.
A.4. Example of a Detailed Admission Control (Congestion Notification)
Operation in Egress Nodes
This appendix describes an example of a detailed admission control
(congestion notification) operation in Egress nodes.
The admission control congestion notification procedure can be
applied only if the Egress maintains the Ingress/Egress pair
aggregate. When the operation state of the Ingress/Egress pair
aggregate is the "congestion notification", see Appendix A.2, then
the implementation of the algorithm depends on how the congestion
notification situation is notified to the Egress. As mentioned in
Appendix A.3, two methods are used:
* using the "notified DSCP". During a measurement interval T, the
Egress counts the number of "notified DSCP" marked bytes that
belong to the same PHB and are associated with the same
Ingress/Egress pair aggregate, say input_notified_bytes. We
denote the rate as incoming_notified_rate.
* using the "encoded DSCP". In this case, during a measurement
interval T, the Egress measures the input_notified_bytes by
counting the "encoded DSCP" bytes.
Below only the detail description of the first method is given.
The incoming congestion_rate can be then calculated as follows:
incoming_congestion_rate = input_notified_bytes/T
If the incoming_congestion_rate is higher than a preconfigured
congestion notification threshold, then the communication path
between Ingress and Egress is considered to be congested. Note that
the pre-congestion notification threshold can be set to "0". In this
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case, the Egress node will operate in congestion notification state
at the moment that it receives at least one "notified DSCP" encoded
packet.
When the Egress node operates in "congestion notification" state and
if the end-to-end RESERVE (probe) arrives at the Egress, then this
request SHOULD be rejected. Note that this happens only when the
probe packet is either "notified DSCP" or "encoded DSCP" marked. In
this way, it is ensured that the end-to-end RESERVE (probe) packet
passed through the node that is congested. This feature is very
useful when ECMP-based routing is used to detect only flows that are
passing through the congested router.
If such an Ingress/Egress pair aggregated state is not available when
the (probe) RESERVE message arrives at the Egress, then this request
is accepted if the DSCP of the packet carrying the RESERVE message is
unmarked. Otherwise (if the packet is either "notified DSCP" or
"encoded DSCP" marked), it is rejected.
A.5. Example of Selecting Bidirectional Flows for Termination during
Severe Congestion
This appendix describes an example of selecting bidirectional flows
for termination during severe congestion.
When a severe congestion occurs, e.g., in the forward path, and when
the algorithm terminates flows to solve the severe congestion in the
forward path, then the reserved bandwidth associated with the
terminated bidirectional flows is also released. Therefore, a
careful selection of the flows that have to be terminated SHOULD take
place. A possible method of selecting the flows belonging to the
same priority type passing through the severe congestion point on a
unidirectional path can be the following:
* the Egress node SHOULD select, if possible, first unidirectional
flows instead of bidirectional flows.
* the Egress node SHOULD select, if possible, bidirectional flows
that reserved a relatively small amount of resources on the path
reversed to the path of congestion.
A.6. Example of a Severe Congestion Solution for Bidirectional Flows
Congested Simultaneously on Forward and Reverse Paths
This appendix describes an example of a severe congestion solution
for bidirectional flows congested simultaneously on forward and
reverse paths.
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This scenario describes a solution using the combination of the
severe congestion solutions described in Section 4.6.2.5.2. It is
considered that the severe congestion occurs simultaneously in
forward and reverse directions, which MAY affect the same
bidirectional flows.
When the QNE Edges maintain per-flow intra-domain QoS-NSLP
operational states, the steps can be the following, see Figure A.3.
Consider that the Egress node selects a number of bidirectional flows
to be terminated. In this case, the Egress will send, for each
bidirectional flow, a NOTIFY message to Ingress. If the Ingress
receives these NOTIFY messages and its operational state (associated
with reverse path) is in the severe congestion state (see Figures 26
and 27), then the Ingress operates in the following way:
* For each NOTIFY message, the Ingress SHOULD identify the
bidirectional flows that have to be terminated.
* The Ingress then calculates the total bandwidth that SHOULD be
released in the reverse direction (thus not in forward direction)
if the bidirectional flows will be terminated (preempted), say
"notify_reverse_bandwidth". This bandwidth can be calculated by
the sum of the bandwidth values associated with all the end-to-end
sessions that received a (severe congestion) NOTIFY message.
* Furthermore, using the received marked packets (from the reverse
path) the Ingress will calculate, using the algorithm used by an
Egress and described in Appendix A.2, the total bandwidth that has
to be terminated in order to solve the congestion in the reverse
path direction, say "marked_reverse_bandwidth".
* The Ingress then calculates the bandwidth of the additional flows
that have to be terminated, say "additional_reverse_bandwidth", in
order to solve the severe congestion in reverse direction, by
taking into account:
** the bandwidth in the reverse direction of the bidirectional flows
that were appointed by the Egress (the ones that received a NOTIFY
message) to be preempted, i.e., "notify_reverse_bandwidth".
** the total amount of bandwidth in the reverse direction that has
been calculated by using the received marked packets, i.e.,
"marked_reverse_bandwidth".
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QNE(Ingress) NE (int.) NE (int.) NE (int.) QNE(Egress)
NTLP stateful NTLP stateful
data| user | | | |
--->| data | #unmarked bytes| | |
|--------------->S #marked bytes | | |
| S--------------------------->| |
| | | |-------------->|data
| | | | |--->
| | | | Term.?
| NOTIFY | | |Yes
|<------------------------------------------------------------|
| | | | |data
| | | user | |<---
| user data | | data |<--------------|
| (#marked bytes)| S<----------| |
|<--------------------------------S | |
| (#unmarked bytes) S | |
Term|<--------------------------------S | |
Flow? | S | |
YES |RESERVE(RMD-QSPEC): S | |
|"forward - T tear" s | |
|--------------->| RESERVE(RMD-QSPEC): | |
| | "forward - T tear" | |
| |--------------------------->| |
| | S |-------------->|
| | S RESERVE(RMD-QSPEC):
| | S "reverse - T tear" |
| RESERVE(RMD-QSPEC) S |<--------------|
| "reverse - T tear" S<----------| |
|<--------------------------------S | |
Figure 28: Intra-domain RMD severe congestion handling for
bidirectional reservation (congestion in both forward
and reverse direction)
This additional bandwidth can be calculated using the following
algorithm:
IF ("marked_reverse_bandwidth" > "notify_reverse_bandwidth") THEN
"additional_reverse_bandwidth" =
= "marked_reverse_bandwidth"- "notify_reverse_bandwidth";
ELSE
"additional_reverse_bandwidth" = 0
* Ingress terminates the flows that experienced a severe congestion
in the forward path and received a (severe congestion) NOTIFY
message.
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* If possible, the Ingress SHOULD terminate unidirectional flows
that use the same Egress-Ingress reverse direction
communication path to satisfy the release of a total bandwidth
up equal to the "additional_reverse_bandwidth", see Appendix
A.5.
* If the number of REQUIRED unidirectional flows (to satisfy the
above issue) is not available, then a number of bidirectional
flows that are using the same Egress-Ingress reverse direction
communication path MAY be selected for preemption in order to
satisfy the release of a total bandwidth equal up to the
"additional_reverse_bandwidth". Note that using the guidelines
given in Appendix A.5, first the bidirectional flows that
reserved a relatively small amount of resources on the path
reversed to the path of congestion SHOULD be selected for
termination.
When the QNE Edges maintain aggregated intra-domain QoS-NSLP
operational states, the steps can be the following.
* The Egress calculates the bandwidth to be terminated using the
same method as described in Section 4.6.1.6.2.2. The Egress
includes this bandwidth value in a <PDR Bandwidth> within a
"PDR_Congestion_Report" container that is carried by the end-
to-end NOTIFY message.
* The Ingress receives the NOTIFY message and reads the <PDR
Bandwidth> value included in the "PDR_Congestion_Report"
container. Note that this value is denoted as
"notify_reverse_bandwidth" in the situation that the QNE Edges
maintain per-flow intra-domain QoS-NSLP operational states, but
is calculated differently. The variables
"marked_reverse_bandwidth" and "additional_reverse_bandwidth"
are calculated using the same steps as explained for the
situation that the QNE Edges maintain per-flow intra-domain
QoS-NSLP states.
* Regarding the termination of flows that use the same Egress-
Ingress reverse direction communication path, the Ingress can
follow the same procedures as the situation that the QNE Edges
maintain per-flow intra-domain QoS-NSLP operational states.
The RMD-aggregated (reduced-state) reservations maintained by
the Interior nodes, can be reduced in the "forward" and
"reverse" directions by using the procedure described in
Section 4.6.2.3 and including in the <Peak Data Rate-1 (p)>
value of the local RMD-QSPEC <TMOD-1> parameter of the RMD-QOSM
<QoS Desired> field carried by the forward intra-domain RESERVE
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the value equal to <notify_reverse_bandwidth> and by including
the <additional_reverse_bandwidth> value in the <PDR Bandwidth>
parameter within the "PDR_Release_Request" container that is
carried by the same intra-domain RESERVE message.
A.7. Example of Preemption Handling during Admission Control
This appendix describes an example of how preemption handling is
supported during admission control.
This section describes the mechanism that can be supported by the QNE
Ingress, QNE Interior, and QNE Egress nodes to satisfy preemption
during the admission control process.
This mechanism uses the preemption building blocks specified in
[RFC5974].
A.7.1. Preemption Handling in QNE Ingress Nodes
If a QNE Ingress receives a RESERVE for a session that causes other
session(s) to be preempted, for each of these to-be-preempted
sessions, then the QNE Ingress follows the following steps:
Step_1:
The QNE Ingress MUST send a tearing RESERVE downstream and add a
BOUND-SESSION-ID, with <Binding_Code> value equal to "Indicated
session caused preemption" that indicates the SESSION-ID of the
session that caused the preemption. Furthermore, an <INFO-SPEC>
object with error code value equal to "Reservation preempted" has to
be included in each of these tearing RESERVE messages.
The selection of which flows have to be preempted can be based on
predefined policies. For example, this selection process can be
based on the MRI associated with the high and low priority sessions.
In particular, the QNE Ingress can select low(er) priority session(s)
where their MRI is "close" (especially the target IP) to the one
associated with the higher priority session. This means that
typically the high priority session and the to-be-preempted lower
priority sessions are following the same communication path and are
passing through the same QNE Egress node.
Furthermore, the amount of lower priority sessions that have to be
preempted per each high priority session, has to be such that the
requested resources by the higher priority session SHOULD be lower or
equal than the sum of the reserved resources associated with the
lower priority sessions that have to be preempted.
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Step_2:
For each of the sent tearing RESERVE(s) the QNE Ingress will send a
NOTIFY message with an <INFO-SPEC> object with error code value equal
to "Reservation preempted" towards the QNI.
Step_3:
After sending the preempted (tearing) RESERVE(s), the Ingress QNE
will send the (reserving) RESERVE, which caused the preemption,
downstream towards the QNE Egress.
A.7.2. Preemption Handling in QNE Interior Nodes
The QNE Interior upon receiving the first (tearing) RESERVE that
carries the <BOUND-SESSION-ID> object with <Binding_Code> value equal
to "Indicated session caused preemption" and an <INFO-SPEC> object
with error code value equal to "Reservation preempted" it considers
that this session has to be preempted.
In this case, the QNE Interior creates a so-called "preemption
state", which is identified by the SESSION-ID carried in the
preemption-related <BOUND-SESSION-ID> object. Furthermore, this
"preemption state" will include the SESSION-ID of the session
associated with the (tearing) RESERVE. Subsequently, if additional
tearing RESERVE(s) are arriving including the same values of BOUND-
SESSION-ID and <INFO-SPEC> objects, then the associated SESSION-IDs
of these (tearing) RESERVE message will be included in the already
created "preemption state". The QNE will then set a timer, with a
value that is high enough to ensure that it will not expire before
the (reserving) RESERVE arrives.
Note that when the "preemption state" timer expires, the bandwidth
associated with the preempted session(s) will have to be released,
following a normal RMD-QOSM bandwidth release procedure. If the QNE
Interior node will not receive all the to-be-preempted (tearing)
RESERVE messages sent by the QNE Ingress before their associated
(reserving) RESERVE message arrives, then the (reserving) RESERVE
message will not reserve any resources and this message will be "M"
marked (see Section 4.6.1.2). Note that this situation is not a
typical situation. Typically, this situation can only occur when at
least one of (tearing) the RESERVE messages is dropped due to an
error condition.
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Otherwise, if the QNE Interior receives all the to-be-preempted
(tearing) RESERVE messages sent by the QNE Ingress, then the QNE
Interior will remove the pending resources, and make the new
reservation using normal RMD-QOSM bandwidth release and reservation
procedures.
A.7.3. Preemption Handling in QNE Egress Nodes
Similar to the QNE Interior operation, the QNE Egress, upon receiving
the first (tearing) RESERVE that carries the <BOUND-SESSION-ID>
object with the <Binding_Code> value equal to "Indicated session
caused preemption" and an <INFO-SPEC> object with error code value
equal to "Reservation preempted", it considers that this session has
to be preempted. Similar to the QNE Interior operation the QNE
Egress creates a so called "preemption state", which is identified by
the SESSION-ID carried in the preemption-related <BOUND-SESSION-ID>
object. This "preemption state" will store the same type of
information and use the same timer value as specified in Appendix
A.7.2.
Subsequently, if additional tearing RESERVE(s) are arriving including
the same values of BOUND-SESSION-ID and <INFO-SPEC> objects, then the
associated SESSION-IDs of these (tearing) RESERVE message will be
included in the already created "preemption state".
If the (reserving) RESERVE message sent by the QNE Ingress node
arrived and is not "M" marked, and if all the to-be-preempted
(tearing) RESERVE messages arrived, then the QNE Egress will remove
the pending resources and make the new reservation using normal RMD-
QOSM procedures.
If the QNE Egress receives an "M" marked RESERVE message, then the
QNE Egress will use the normal partial RMD-QOSM procedure to release
the partial reserved resources associated with the "M" marked RESERVE
(see Section 4.6.1.2).
If the QNE Egress will not receive all the to-be-preempted (tearing)
RESERVE messages sent by the QNE Ingress before their associated and
not "M" marked (reserving) RESERVE message arrives, then the
following steps can be followed:
* If the QNE Egress uses an end-to-end QOSM that supports the
preemption handling, then the QNE Egress has to calculate and
select new lower priority sessions that have to be terminated.
How the preempted sessions are selected and signaled to the
downstream QNEs is similar to the operation specified in Appendix
A.7.1.
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* If the QNE Egress does not use an end-to-end QOSM that supports
the preemption handling, then the QNE Egress has to reject the
requesting (reserving) RESERVE message associated with the high
priority session (see Section 4.6.1.2).
Note that typically, the situation in which the QNE Egress does not
receive all the to-be-preempted (tearing) RESERVE messages sent by
the QNE Ingress can only occur when at least one of the (tearing)
RESERVE messages are dropped due to an error condition.
A.8. Example of a Retransmission Procedure within the RMD Domain
This appendix describes an example of a retransmission procedure that
can be used in the RMD domain.
If the retransmission of intra-domain RESERVE messages within the RMD
domain is not disallowed, then all the QNE Interior nodes SHOULD use
the functionality described in this section.
In this situation, we enable QNE Interior nodes to maintain a replay
cache in which each entry contains the <RSN>, <SESSION-ID> (available
via GIST), <REFRESH-PERIOD> (available via the QoS NSLP [RFC5974]),
and the last received "PHR Container" <Parameter ID> carried by the
RMD-QSPEC for each session [RFC5975]. Thus, this solution uses
information carried by <QoS-NSLP> objects [RFC5974] and parameters
carried by the RMD-QSPEC "PHR Container". The following phases can
be distinguished:
Phase 1: Create Replay Cache Entry
When an Interior node receives an intra-domain RESERVE message and
its cache is empty or there is no matching entry, it reads the
<Parameter ID> field of the "PHR Container" of the received message.
If the <Parameter ID> is a PHR_RESOURCE_REQUEST, which indicates that
the intra-domain RESERVE message is a reservation request, then the
QNE Interior node creates a new entry in the cache and copies the
<RSN>, <SESSION-ID> and <Parameter ID> to the entry and sets the
<REFRESH-PERIOD>.
By using the information stored in the list, the Interior node
verifies whether or not the received intra-domain RESERVE message is
sent by an adversary. For example, if the <SESSION-ID> and <RSN> of
a received intra-domain RESERVE message match the values stored in
the list then the Interior node checks the <Parameter ID> part.
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If the <Parameter ID> is different, then:
Situation D1: <Parameter ID> in its own list is
PHR_RESOURCE_REQUEST, and <Parameter ID> in the message is
PHR_REFRESH_UPDATE;
Situation D2: <Parameter ID> in its own list is
PHR_RESOURCE_REQUEST or PHR_REFRESH_UPDATE, and <Parameter ID>
in the message is PHR_RELEASE_REQUEST;
Situation D3: <Parameter ID> in its own list is PHR_REFRESH_UPDATE,
and <Parameter ID> in the message is PHR_RESOURCE_REQUEST;
For Situation D1, the QNE Interior node processes this message by
RMD-QOSM default operation, reserves bandwidth, updates the entry,
and passes the message to downstream nodes. For Situation D2, the
QNE Interior node processes this message by RMD-QOSM default
operation, releases bandwidth, deletes all entries associated with
the session and passes the message to downstream nodes. For
situation D3, the QNE Interior node does not use/process the local
RMD-QSPEC <TMOD-1> parameter carried by the received intra-domain
RESERVE message. Furthermore, the <K> flag in the "PHR Container"
has to be set such that the local RMD-QSPEC <TMOD-1> parameter
carried by the intra-domain RESERVE message is not processed/used by
a QNE Interior node.
If the <Parameter ID> is the same, then:
Situation S1: <Parameter ID> is equal to PHR_RESOURCE_REQUEST;
Situation S2: <Parameter ID> is equal to PHR_REFRESH_UPDATE;
For situation S1, the QNE Interior node does not process the
intra-domain RESERVE message, but it just passes it to downstream
nodes, because it might have been retransmitted by the QNE Ingress
node. For situation S2, the QNE Interior node processes the first
incoming intra-domain (refresh) RESERVE message within a refresh
period and updates the entry and forwards it to the downstream
nodes.
If only <Session-ID> is matched to the list, then the QNE Interior
node checks the <RSN>. Here also two situations can be
distinguished:
If a rerouting takes place (see Section 5.2.5.2 in [RFC5974]), the
<RSN> in the message will be equal to either <RSN + 2> in the stored
list if it is not a tearing RESERVE or <RSN -1> in the stored list if
it is a tearing RESERVE:
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The QNE Interior node will check the <Parameter ID> part;
If the <RSN> in the message is equal to <RSN + 2> in the stored list
and the <Parameter ID> is a PHR_RESOURCE_REQUEST or
PHR_REFRESH_UPDATE, then the received intra-domain RESERVE message
has to be interpreted and processed as a typical (non-tearing)
RESERVE message, which is caused by rerouting, see Section 5.2.5.2 in
[RFC5974].
If the <RSN> in the message is equal to <RSN-1> in the stored list
and the <Parameter ID> is a PHR_RELEASE_REQUEST, then the received
intra-domain RESERVE message has to be interpreted and processed as a
typical (tearing) RESERVE message, which is caused by rerouting (see
Section 5.2.5.2 in [RFC5974]).
If other situations occur than the ones described above, then the QNE
Interior node does not use/process the local RMD-QSPEC <TMOD-1>
parameter carried by the received intra-domain RESERVE message.
Furthermore, the <K> parameter has to be set, see above.
Phase 2: Update Replay Cache Entry
When a QNE Interior node receives an intra-domain RESERVE message, it
retrieves the corresponding entry from the cache and compares the
values. If the message is valid, the Interior node will update
<Parameter ID> and <REFRESH-PERIOD> in the list entry.
Phase 3: Delete Replay Cache Entry
When a QNE Interior node receives an intra-domain (tear) RESERVE
message and an entry in the replay cache can be found, then the QNE
Interior node will delete this entry after processing the message.
Furthermore, the Interior node will delete cache entries, if it did
not receive an intra-domain (refresh) RESERVE message during the
<REFRESH-PERIOD> period with a <Parameter ID> value equal to
PHR_REFRESH_UPDATE.
A.9. Example on Matching the Initiator QSPEC to the Local RMD-QSPEC
Section 3.4 of [RFC5975] describes an example of how the QSPEC can be
Used within QoS-NSLP. Figure 29 illustrates a situation where a QNI
and a QNR are using an end-to-end QOSM, denoted in this context as
Z-e2e. It is considered that the QNI access network side is a
wireless access network built on a generation "X" technology with QoS
support as defined by generation "X", while QNR access network is a
wired/fixed access network with its own defined QoS support.
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Furthermore, it is considered that the shown QNE Edges are located at
the boundary of an RMD domain and that the shown QNE Interior nodes
are located inside the RMD domain.
The QNE Edges are able to run both the Z-e2e QOSM and the RMD-QOSM,
while the QNE Interior nodes can only run the RMD-QOSM. The QNI is
considered to be a wireless laptop, for example, while the QNR is
considered to be a PC.
|------| |------| |------| |------|
|Z-e2e |<->|Z-e2e |<------------------------->|Z-e2e |<->|Z-e2e |
| QOSM | | QOSM | | QOSM | | QOSM |
| | |------| |-------| |-------| |------| | |
| NSLP | | NSLP |<->| NSLP |<->| NSLP |<->| NSLP | | NSLP |
|Z-e2e | | RMD | | RMD | | RMD | | RMD | | Z-e2e|
| QOSM | | QOSM | | QOSM | | QOSM | | QOSM | | QOSM |
|------| |------| |-------| |-------| |------| |------|
-----------------------------------------------------------------
|------| |------| |-------| |-------| |------| |------|
| NTLP |<->| NTLP |<->| NTLP |<->| NTLP |<->| NTLP |<->| NTLP |
|------| |------| |-------| |-------| |------| |------|
QNI QNE QNE QNE QNE QNR
(End) (Ingress Edge) (Interior) (Interior) (Egress Edge) (End)
Figure 29. Example of initiator and local domain QOSM operation
The QNI sets <QoS Desired> and <QoS Available> QSPEC objects in the
initiator QSPEC, and initializes <QoS Available> to <QoS Desired>.
In this example, the <Minimum QoS> object is not populated. The QNI
populates QSPEC parameters to ensure correct treatment of its traffic
in domains down the path. Additionally, to ensure correct treatment
further down the path, the QNI includes <PHB Class> in <QoS Desired>.
The QNI therefore includes in the QSPEC.
<QoS Desired> = <TMOD-1> <PHB Class>
<QoS Available> = <TMOD-1> <Path Latency>
In this example, it is assumed that the <TMOD-1> parameter is used to
encode the traffic parameters of a VoIP application that uses RTP and
the G.711 Codec, see Appendix B in [RFC5975]. The below text is
copied from [RFC5975].
In the simplest case the Minimum Policed Unit m is the sum of the
IP-, UDP- and RTP- headers + payload. The IP header in the IPv4
case has a size of 20 octets (40 octets if IPv6 is used). The UDP
header has a size of 8 octets and RTP uses a 12 octet header. The
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G.711 Codec specifies a bandwidth of 64 kbit/s (8000 octets/s).
Assuming RTP transmits voice datagrams every 20 ms, the payload
for one datagram is 8000 octets/s * 0.02 s = 160 octets.
IPv4+UDP+RTP+payload: m=20+8+12+160 octets = 200 octets
IPv6+UDP+RTP+payload: m=40+8+12+160 octets = 220 octets
The Rate r specifies the amount of octets per second. 50
datagrams are sent per second.
IPv4: r = 50 1/s * m = 10,000 octets/s
IPv6: r = 50 1/s * m = 11,000 octets/s
The bucket size b specifies the maximum burst. In this example, a
burst of 10 packets is used.
IPv4: b = 10 * m = 2000 octets
IPv6: b = 10 * m = 2200 octets
In our example, we will assume that IPV4 is used and therefore, the
<TMOD-1> values will be set as follows:
m = 200 octets
r = 10000 octets/s
b = 2000 octets
The <Peak Data Rate-1 (p)> and MPS are not specified above, but in
our example we will assume:
p = r = 10000 octets/s
MPS = 220 octets
The <PHB Class> is set in such a way that the Expedited Forwarding
(EF) PHB is used.
Since <Path Latency> and <QoS Class> are not vital parameters from
the QNI's perspective, it does not raise their <M> flags.
Each QNE, which supports the Z-e2e QOSM on the path, reads and
interprets those parameters in the initiator QSPEC.
When an end-to-end RESERVE message is received at a QNE Ingress node
at the RMD domain border, the QNE Ingress can "hide" the initiator
end-to-end RESERVE message so that only the QNE Edges process the
initiator (end-to-end) RESERVE message, which then bypasses
intermediate nodes between the Edges of the domain, and issues its
own local RESERVE message (see Section 6). For this new local
RESERVE message, the QNE Ingress node generates the local RMD-QSPEC.
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The RMD-QSPEC corresponding to the RMD-QOSM is generated based on the
original initiator QSPEC according to the procedures described in
Section 4.5 of [RFC5974] and in Section 6 of this document. The RMD
QNE Ingress maps the <TMOD-1> parameters contained in the original
Initiator QSPEC into the equivalent <TMOD-1> parameter representing
only the peak bandwidth in the local RMD-QSPEC.
In this example, the initial <TMOD-1> parameters are mapped into the
RMD-QSPEC <TMOD-1> parameters as follows.
As specified, the RMD-QOSM bandwidth equivalent <TMOD-1> parameter of
RMD-QSPEC should have:
r = p of initial e2e <TMOD-1> parameter
m = large;
b = large;
For the RMD-QSPEC <TMOD-1> parameter, the following values are
calculated:
r = p of initial e2e <TMOD-1> parameter = 10000 octets/s
m is set in this example to large as follows:
m = MPS of initial e2e <TMOD-1> parameter = 220 octets
The maximum value of b = 250 gigabytes, but in our example this value
is quite large. The b parameter specifies the extent to which the
data rate can exceed the sustainable level for short periods of time.
In order to get a large b, in this example we consider that for a
period of certain period of time the data rate can exceed the
sustainable level, which in our example is the peak rate (p).
Thus, in our example, we calculate b as:
b = p * "period of time"
For this VoIP example, we can assume that this period of time is 1.5
seconds, see below:
b = 10000 octets/s * 1.5 seconds = 15000 octets
Thus, the local RMD-QSPEC <TMOD-1> values are:
r = 10000 octets/s
p = 10000 octets/s
m = 220 octets
b = 15000 octets
MPS = 220 octets
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The bit level format of the RMD-QSPEC is given in Section 4.1. In
particular, the Initiator/Local QSPEC bit, i.e., <I> is set to
"Local" (i.e., "1") and the <Qspec Proc> is set as follows:
* Message Sequence = 0: Sender initiated
* Object combination = 0: <QoS Desired> for RESERVE and
<QoS Reserved> for RESPONSE
The <QSPEC Version> used by RMD-QOSM is the default version, i.e.,
"0", see [RFC5975]. The <QSPEC Type> value used by the RMD-QOSM is
specified in [RFC5975] and is equal to: "2".
The <Traffic Handling Directives> contains the following fields:
<Traffic Handling Directives> = <PHR container> <PDR container>
The Per-Hop Reservation container (PHR container) and the Per-Domain
Reservation container (PDR container) are specified in Sections 4.1.2
and 4.1.3, respectively. The <PHR container> contains the traffic
handling directives for intra-domain communication and reservation.
The <PDR container> contains additional traffic handling directives
that are needed for edge-to-edge communication. The RMD-QOSM <QoS
Desired> and <QoS Reserved>, are specified in Section 4.1.1.
In RMD-QOSM the <QoS Desired> and <QoS Reserved> objects contain the
following parameters:
<QoS Desired> = <TMOD-1> <PHB Class> <Admission Priority>
<QoS Reserved> = <TMOD-1> <PHB Class> <Admission Priority>
The bit format of the <PHB Class> (see [RFC5975] and Figures 4 and 5)
and <Admission Priority> complies to the bit format specified in
[RFC5975].
In this example, the RMD-QSPEC <TMOD-1> values are the ones that were
calculated and given above. Furthermore, the <PHB Class>, represents
the EF PHB class. Moreover, in this example the RMD reservation is
established without an <Admission Priority> parameter, which is
equivalent to a reservation established with an <Admission Priority>
whose value is 1.
The RMD QNE Egress node updates <QoS Available> on behalf of the
entire RMD domain if it can. If it cannot (since the <M> flag is not
set for <Path Latency>) it raises the parameter-specific, "not-
supported" flag, warning the QNR that the final latency value in <QoS
Available> is imprecise.
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In the "Y" access domain, the initiator QSPEC is processed by the QNR
in the similar was as it was processed in the "X" wireless access
domain, by the QNI.
If the reservation was successful, eventually the RESERVE request
arrives at the QNR (otherwise, the QNE at which the reservation
failed would have aborted the RESERVE and sent an error RESPONSE back
to the QNI). If the <RII> was included in the QoS-NSLP message, the
QNR generates a positive RESPONSE with QSPEC objects <QoS Reserved>
and <QoS Available>. The parameters appearing in <QoS Reserved> are
the same as in <QoS Desired>, with values copied from <QoS
Available>. Hence, the QNR includes the following QSPEC objects in
the RESPONSE message:
<QoS Reserved> = <TMOD-1> <PHB Class>
<QoS Available> = <TMOD-1> <Path Latency>
Contributors
Attila Takacs
Ericsson Research
Ericsson Hungary Ltd.
Laborc 1, Budapest, Hungary, H-1037
EMail: Attila.Takacs@ericsson.com
Andras Csaszar
Ericsson Research
Ericsson Hungary Ltd.
Laborc 1, Budapest, Hungary, H-1037
EMail: Andras.Csaszar@ericsson.com
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Authors' Addresses
Attila Bader
Ericsson Research
Ericsson Hungary Ltd.
Laborc 1, Budapest, Hungary, H-1037
EMail: Attila.Bader@ericsson.com
Lars Westberg
Ericsson Research
Torshamnsgatan 23
SE-164 80 Stockholm, Sweden
EMail: Lars.Westberg@ericsson.com
Georgios Karagiannis
University of Twente
P.O. Box 217
7500 AE Enschede, The Netherlands
EMail: g.karagiannis@ewi.utwente.nl
Cornelia Kappler
ck technology concepts
Berlin, Germany
EMail: cornelia.kappler@cktecc.de
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
EMail: Hannes.Tschofenig@nsn.com
URI: http://www.tschofenig.priv.at
Tom Phelan
Sonus Networks
250 Apollo Dr.
Chelmsford, MA 01824 USA
EMail: tphelan@sonusnet.com
Bader, et al. Experimental [Page 128]