NSIS Working Group Attila Bader
INTERNET-DRAFT Lars Westberg
Ericsson
Expires: 24 May 2006 Georgios Karagiannis
University of Twente
Cornelia Kappler
Siemens
Tom Phelan
Sonus
October 24, 2005
RMD-QOSM - The Resource Management in Diffserv QOS Model
<draft-ietf-nsis-rmd-04.txt>
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes an NSIS QoS Model for networks that use the
Resource Management in Diffserv (RMD) concept. RMD is a technique
for adding admission control 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
Bader, et al. [Page 1]
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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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . .3
3. Overview of RMD and RMD-QOSM . . . . . . . . . . . . . .. . .4
3.1 RMD . . . . . . . . . . . . . . . . . . . . . . . . . . .4
3.2 Basic features of RMD-QOSM . . . . . . . . . . . . . . . 6
3.2.1 Role of the QNEs . . . . . . . .. . . . . . . . . .6
3.2.2 RMD-QOSM signaling . . . . . . . . . . . . . . . . 7
4. RMD-QOSM, Detailed Description . . . . . . . . . . . .. . . .8
4.1 RMD-QSpec Definition . . . . . . . . . . . . . . . . . . 8
4.1.1 RMD-QOSM QoS Description . . . . . . . . . . . . .9
4.1.2 PHR RMD-QOSM control information . . . . . . . . . 9
4.1.3 PDR RMD-QOSM control information . . . . . . . . 11
4.1.4 Mapping of QSpec parameters onto generic
QSpec Parameters . . . . . . . . . . . . . . . . .12
4.2 Message format . . . . . . . . . . . . . . . . . . . . .13
4.3 RMD node state management . . . . . . . . . . . . . . . 14
4.3.1 Aggregated versus per flow reservations at the
QNE edges . . . . . . . . . . . . . . . . . . . . 14
4.3.2 Measurement-based method . . . . . . . . . . . . .15
4.3.3 Reservation-based method . .. . . . . . . . . . . 15
4.4 Transport of RMD-QOSM messages . . . . . . . . . . . . .16
4.5 Edge discovery and addressing of messages . . . . . . . 16
4.6 Operation and sequence of events . . . . . . . . . . . .16
4.6.1 Basic unidirectional operation . . . . . . . . . .17
4.6.1.1 Successful reservation. . . . . . . . . . . .17
4.6.1.2 Unsuccessful reservation . . . . . . . . . . 22
4.6.1.3 RMD refresh reservation. . . . . . . . . . . 24
4.6.1.4 RMD modification of aggregated reservation . 27
4.6.1.5 RMD release procedure. . . . . . . . . . . . 28
4.6.1.6 Severe congestion handling . . . . . . . . .34
4.6.2 Bidirectional operation . . . . . . . . . . . . . 38
4.6.2.1 Successful and unsuccessful reservation . . .39
4.6.2.2 Refresh reservation . . . . . . . . . . . . .43
4.6.2.3 Modification of aggregated reservation . . . 44
4.6.2.4 Release procedure . . . . . . . . . . . . . .45
4.6.2.5 Severe congestion handling . . . . . . . . . 45
4.7 Handling of additional errors . . . . . . . . . . . . . 49
5. Security Consideration. . . . . . . . . . . . . . . . . . . 49
6. IANA Considerations. . . . . . . . . . . . . . . . . . . . .53
7. Open issues. . . . . . . . . . . . . . . . . . . . . . . . .53
8. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . .53
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9. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . 54
10. Normative References . . . . . . . . . . . . . . . . . . . 55
11. Informative References . . . . . . . . . . . . . . . . . . 55
12. Intellectual Property Rights . . . . . . . . . . . . . . . 57
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]). 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)
[QoS-NSLP] specifies a generic model for carrying Quality of Service
(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) 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
Internally to the RMD network, RMD-QOSM defines a scalable QoS
signaling model in which per-flow QoS-NSLP and NTLP states are not
stored in Interior nodes but per-flow signaling is performed (see
[QoS-NSLP]).
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In the RMD-QOSM, only routers at the edges of a Diffserv domain
(Ingress and Egress nodes) support the QoS-NSLP stateful operation.
Interior nodes support either the QoS-NSLP stateless operation, or a
reduced-state operation with coarser granularity than the edge nodes.
The remainder of this draft is structured following the suggestions
in Appendix B of [QSP-T] for the description of QoS Signaling
Policies.
After the terminology in Section 2, we give an overview of RMD and
the RMD-QOSM in Section 3. In Section 4 we give a detailed
description of the RMD-QOSM, including the role of 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 RFC 2119.
The terminology defined by GIMPS [GIMPS] and QoS-NSLP [QoS-NSLP]
applies to this draft.
In addition, the following terms are used:
Edge node: an (NSIS-capable) node on the boundary of some
administrative domain.
Ingress node: An edge node that handles the traffic as it enters the
domain.
Egress node: An edge node that handles the traffic as it leaves the
domain.
Interior nodes: the set of (NSIS-capable) nodes which form an
administrative domain, excluding the edge nodes.
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
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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 way for devices
outside the domain to dynamically reserve resources or receive
indications of network resource availability. In practice, service
providers rely on subscription-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. In particular, 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.
In RMD two basic admission control modes are described: measurement-
based and reservation-based admission control. 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. Once
an admission decision is made, no record of the decision need be
kept. The advantage of measurement-based resource management
protocols is that they do not require pre-reservation state or
explicit release of the reservations. 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.
With the reservation-based method, each Interior node maintains
only one reservation state per traffic class. The Ingress edge
nodes aggregate individual flow requests into classes, and signal
changes in the class reservations as necessary. The reservation is
quantified in terms of resource units. 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.
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RMD describes the following procedures:
* classification of individual resource reservation or resource
query into Per Hop Behavior groups (PHB) at the Ingress node of
the domain,
* hop-by-hop admission control based on per 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 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 QNI and 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 QoS-NSLP aware nodes. Edge nodes
store and maintain QoS-NSLP and NTLP states and therefore are
stateful nodes. The Interior nodes are NTLP stateless. Furthermore
they are either QoS-NSLP stateless (for measurement-based
operation), or are reduced state nodes storing per PHB aggregated
QoS-NSLP states (for reservation-based operation).
Note that the RMD-QOSM 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
operation (see Section 4.6.1.6).
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INTERNET-DRAFT RMD-QOSM
|------| |-------| |------| |------|
| 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 signaling
The basic RMD-QOSM signaling is shown in Figure 3. A RESERVE
message is created by a QNI with an Initiator QSpec describing the
reservation and forwarded along the path towards the QNR. When the
original RESERVE message arrives at the Ingress node, an RMD-QSpec
is constructed based on the top-most QSPEC in the message (usually
the Initiator QSPEC). The RMD-QSpec is sent in a local, independent
RESERVE message through the Interior nodes towards the QNR. This
local RESERVE message uses the NTLP hop-by-hop datagram signaling
mechanism. 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 local RESERVE
message and checks the availability of resources with either the
reservation-based or the measurement-based method. When the message
reaches the Egress node, and the reservation is successful in each
Interior nodes, the original 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.
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 a RESPONSE message is sent directly the Ingress node.
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INTERNET-DRAFT RMD-QOSM
QNE QNE QNE QNE
Ingress Interior Interior Egress
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
RESERVE | | | |
-------->| RESERVE | | |
+--------------------------------------------->|
| RESERVE' | | |
+-------------->| | |
| | RESERVE' | |
| +-------------->| |
| | | RESERVE' |
| | +------------->|
| | | | RESERVE
| | | +------->
| | | |RESPONSE
| | | |<-------
| | | RESPONSE |
|<---------------------------------------------+
RESPONSE| | | |
<--------| | | |
Figure 3: Sender-initiated reservation with Reduced State Interior
Nodes
As a consequence in the stateless/reduced state domain only sender-
initiated reservation can be performed and functions requiring per
flow NTLP or QoS-NSLP states, like summary refreshes, cannot be
used. One of the basic features of RMD is that, if per flow
identification, is needed, i.e. associating the flows IDs for the
reserved resources, Edge nodes act on behalf of Interior nodes.
4. RMD-QOSM, Detailed Description
This section describes 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 RMD-QOSM QoS-NSLP messages
and how QSpecs are processed and used in different protocol
operations.
4.1. RMD-QSpec Definition
The RMD-QOSM QSpec object contains three fields, the "RMD-QOSM QoS
Description", the Per Hop Reservation "PHR RMD-QOSM control
information" container (PHR container) and the Per Domain Reservation
"PDR RMD-QOSM control information" container (PDR container). The
"RMD-QOSM QoS Description" field and the PHR container are used and
processed by edge and Interior nodes. The PDR container field is
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INTERNET-DRAFT RMD-QOSM
only processed by edge nodes. The PHR container contains the QoS
specific control information for intra-domain communication and
reservation. The PDR container contains additional information that
is needed for edge-to-edge communication.
4.1.1. RMD-QOSM QoS Description
This section describes the parameters used by the "RMD-QOSM QoS
Description" field. The RMD-QOSM QoS Description only contains the
QoS Desired object [QSP-T]. It does not contain the QoS Available,
QoS Reserved or Minimum QoS objects.
<RMD-QOSM QoS Description> = <QoS Desired>
<QoS Desired> = <Bandwidth> <PHB Class Class>
The bit format of the <Bandwidth> and <PHB Class> conform to the
bit format specified in [QSP-T] and can be seen in Figure 4 and
Figure 5, respectively.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|N|T| 3 |r|r|r|r| 1 ||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bandwidth (32-bit IEEE floating point number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Bandwidth parameter
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|E|N|T| 7 |r|r|r|r| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSCP |0 0 0 0 0 0 0 0 0 0| Reserved |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 5: PHB_Class parameter
4.1.2. PHR RMD-QOSM control information container (PHR container)
This section describes the parameters used by the PHR container.
<PHR RMD-QOSM control information> = <Overload %>, <S>,<M>,
<Admitted Hops>, <B>, <Hop_U> <Time Lag>
The bit format of the PHR container can be seen in Figure 6. Note
that in Figure 6 <Hop U> is represented as <U>.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|E|N|T| Container ID |r|r|r|r| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|M| Admitted Hops|B|U| Time Lag | Overload % | Empty|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: PHR container
Parameter/Container ID:
8 bit field, indicating the PHR type: PHR_Resource_Request,
PHR_Release_Request, PHR_Refresh_Update. It is used to further
specify QoS-NSLP RESERVE and RESPONSE messages.
"PHR_Resource_Request" (Parameter/Container ID = 1): 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_Refresh_Update" (Parameter/Container ID = 2): 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.
"PHR_Release_Request" (Parameter/Container ID = 3): explicitly
release, by subtraction, the reserved resources for a particular flow
from a traffic class reservation state.
<S> (Severe Congestion):
1 bit. In 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 sever congestion occurs. Congested Interior nodes SHOULD
notify edge QNEs about the congestion, which is done by setting the
S bit.
<Overload %>:
8 bits In case of severe congestion the level of overload is
indicated by the Overload %. Overload % SHOULD be higher than 0 if
S bit is set. If overload in a node is greater than the overload
in a previous node then Overload % SHOULD be updated.
<M>:
1 bit. In 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.
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<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 is
increased by one at each Interior QNE. 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.
<Hop_U> (NSLP_Hops unset):
1-bit. The QNE(Ingress) node MUST set the <Hop_U> parameter to
0. This parameter MAY 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 "1" the <Admitted Hops> SHOULD NOT be
changed.
<B>: 1 bit. Indicates bi-directional reservation.
<Time Lag>: 8 bit field. The time lag used in a sliding window
over the refresh period.
4.1.3. PDR RMD-QOSM control information container (PDR container)
This section describes the parameters of the PDR container.
The bit format of the PDR container can be seen in Figure 7.
<PDR RMD-QOSM control information> = <Overload %> <S> <M> <Max
Admitted Hops> <B> [<PDR Reverse Requested Resources>]
The bit format of the PDR container can be seen in Figure 7. Note
that in Figure 7 <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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|E|N|T| Container ID |r|r|r|r| 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|M| Max Adm Hops |B| Overload % | Empty |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PDR Reverse Requested Resources(32-bit IEEE floating p.number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: PDR container
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Parameter/Container ID:
8-bit field identifying the type of PDR container field.
"PDR_Reservation_Request" (Parameter/Container ID = 4): generated by
the QNE(Ingress) node in order to initiate or update the QoS-NSLP
per domain reservation state in the QNE(Egress) node
"PDR_Refresh_Request" (Parameter/Container ID = 5): 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/Container ID = 6): 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/Container ID = 7): 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" control information fields have been
received and that the request has been admitted or rejected
"PDR_Refresh_Report" (Parameter/Container ID = 8) generated and sent
by the QNE(Egress) node in case needed, to the QNE(Ingress) node
to report that a "PHR_Refresh_Update" control information
field has been received and has been processed
"PDR_Release_Report" (Parameter/Container ID = 9) 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" control information fields have been
received and have been processed.
"PDR_Congestion_Report" (Parameter/Container ID = 10): 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.
<Overload %>:
8-bit. It includes the Overload % of the
"PHR_Resource_Request" or "PHR_Refresh_Update" control
information fields, indicating the level of overload to the Ingress
node.
<M> (PDR Marked):
1-bit. Carries the <M> value of the "PHR_Resource_Request" or
"PHR_Refresh_Update" control information fields.
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<B>: 1 bit Indicates bi-directional reservation.
<Max Admitted Hops>:
8-bit. The <Admitted Hops> value that has been carried by the
PHR container field used to identify the RMD reservation based node
that admitted or process a "PHR_Resource_Request"
<PDR Reverse Requested Resources>
32 bits. This field only applies when the "B" flag is set to
"1". It specifies the requested number of units of resources
that have to be reserved by a node in the reverse direction
when the intra-domain signaling procedures require a bi-
directional reservation procedure.
4.2. Message format
The format of the messages used by the RMD-QOSM complies with the
QoS-NSLP specification. As specified in [QoS-NSLP], for each
QoS-NSLP message type, there is a set of rules for the permissible
choice of object types. These rules are specified using Backus-Naur
Form (BNF) augmented with square brackets surrounding optional
sub-sequences. The BNF implies an order for the objects in a
message. However, in many (but not all) cases, object order makes no
logical difference. An implementation SHOULD create messages with
the objects in the order shown here, but accept the objects in any
permissible order.
The format of a local (intra-domain) RESERVE message used by the
RMD-QOSM is:
RESERVE = COMMON_HEADER
RSN [ RII ] [ REFRESH_PERIOD ] [ BOUND_SESSION_ID ]
[ POLICY_DATA ] [ RMD-QSPEC]
The format of a Query message used by the RMD-QOSM is as follows:
QUERY = COMMON_HEADER
[ RII ][ BOUND_SESSION_ID ]
[ POLICY_DATA ] [ RMD-QSPEC ]
A QUERY message MUST contain an RII object to indicate a RESPONSE is
desired, unless the QUERY is being used to initiate reverse-path
state for a receiver-initiated reservation.
The format of a local (intra-domain) RESPONSE message used by
the RMD-QOSM is as follows:
intra-domain RESPONSE = COMMON_HEADER
[ RII / RSN ] ERROR_SPEC
[ RMD-QSPEC ]
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The format of an end-to-end RESPONSE message that is used by the
RMD-QOSM to carry an intra-domain RESPONSE message is as follows:
RESPONSE = COMMON_HEADER
[ RII / RSN ] ERROR_SPEC [ RMD-QSPEC ] [ *QSPEC ]
The format of a NOTIFY message used by the
RMD-QOSM is as follows:
NOTIFY = COMMON_HEADER ERROR_SPEC [ RMD-QSPEC ]
All objects, except RMD-QSPEC objects, are specified in [QoS-NSLP].
4.3. RMD node state management
The QoS-NSLP state creation and management is specified in
[QoS-NSLP]. This section describes the state creation and
management functions of the Resource Management Function (RMF) in
the RMD nodes.
4.3.1 Aggregated versus per flow reservations at the QNE edges
The QNE edges maintain for the RMD QoS model either per flow, or
aggregated QoS-NSLP reservation states. Each per flow or aggregated
QoS-NSLP reservation state, associated with the RMD-QOS model, is
identified by a NTLP SESSION_ID (see [GIMPS]). In RMD, these states
are denoted as PDR states.
In the situation where the QNE edges maintain aggregated QoS-
NSLP reservation states then these states have to maintain the
SESSION_ID of the aggregated state, the IP addresses of the Ingress
and Egress nodes, the PHB value and the size of the aggregated
reservation, e.g., reserved bandwidth.
The size of the aggregation is defined as it is specified in Section
1.4.4 of [RFC 3175]. 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 it aggregates. Some 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).
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4.3.2 Measurement-based method
QNE Interior nodes operating in measurement-based mode are QoS-NSLP
stateless nodes, i.e., they do not support any QoS-NSLP or
NTLP/GIMPS states. These measurement-based nodes store two
RMD-QOSM states per PHR group. These states reflect traffic
conditions at the node and are not affected by any QoS-NSLP
signaling. One state stores the measured user traffic load
associated with the PHR group and another state stores the
maximum traffic load that can be admitted per PHR group.
When a measurement-based node receives a local 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
QNE Interior nodes operating in reservation-based mode are QoS-NSLP
reduced state nodes, i.e., they do not store NTLP/GIMPS 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 from the QNE Ingress node up to the QNE Egress
node. This state represents the number of currently reserved
resource units. 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.
The per-PHB group reservation states are soft states, which are
refreshed by sending periodic refresh local RESERVE messages. If a
refresh message corresponding to a number of reserved resource units
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 PHR
release message. The usage 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.
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4.4. Transport of RMD-QOSM messages
The intra-domain (local) messages used by the RMD-QOSM MUST operate
in the NTLP/GIMPS Datagram mode (see [GIMPS]). Therefore, the NSLP
functionality available in all QoS NSLP nodes that are able to
support the RMD-QOSM MUST require the intra-domain GIMPS
functionality available in these nodes to operate in the datagram
mode, i.e., require GIMPS to:
* operate in unreliable mode. This can be satisfied by passing this
requirement from the QoS-NSLP layer to the GIMPS layer via the API
transfer-attributes.
* do not create a message association state. This requirement can be
satisfied by a local policy, e.g., the QNE is configured to do not
create a message association state
* do not create any NTLP routing state. This can be satisfied by
passing this requirement from the QoS-NSLP layer to the GIMPS layer
via the API.
All the intra-domain local messages are transported using the GIMPS
data messages (see [GIMPS]). At the 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 the router
alert option. In that case, interior routers are configured to handle
only certain levels of router alert (RAO) values. This is
accomplished by marking the end-to-end RESERVE message, i.e.,
modifying the QoS-NSLP default NSLP-ID value to another NSLP-ID
predefined value.
The marking MUST be accomplished by the ingress by modifying the
QoS_NSLP default NSLP-ID value to a NSLP-ID predefined value. In this
way the egress MUST stop this marking process by reassigning the
QoS-NSLP default NSLP-ID value to the original (end-to-end) RESERVE
message. Note that the assignment of these NSLP-ID values is a QOS-
NSLP issue, which should be accomplished via IANA.
4.5 Edge discovery and addressing of messages
Mainly, the Egress node discovery can be performed either by using
the GIMPS discovery mechanism [GIMPS], manual configuration or any
other discovery technique. The addressing of signaling messages
depends on the used GIMPS transport mode. The RMD QoS signaling
messages that are processed only by the edge nodes use the peer-peer
addressing of the GIMPS connection (C) mode. RMD QoS signaling
messages that are processed by all nodes of the Diffserv domain,
i.e., edges and Interior nodes, use the end-end addressing of the
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GIMPS datagram (D) mode. RMD QoS signaling messages that are
addressed to the data path end nodes are intercepted by the Egress
nodes.
4.6. Operation and sequence of events
This section describes the operation and the sequence of events in
the RMD-QOSM.
4.6.1. Basic unidirectional operation
This section describes the basic unidirectional operation and
sequence of events of the RMD-QOSM. The following basic operation
cases are distinguished: Successful reservation, Unsuccessful
reservation, Refresh, Modification, Release, Severe congestion and
Congestion Notification. 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 edge can also operate as a QNI or as a QNR.
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 [GIMPS].
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
procedures defined by the end-to-end QoS model. Subsequently, the
RMD QoS Description: <Bandwidth> and <PHB Class> are derived from
the QoS Description of the end-to-end QSpec.
As described in Section 4.3.1, the QNE edges maintain for the RMD
QoS model either per flow, or aggregated QoS-NSLP reservation
states, which are identified by (local NTLP) SESSION_IDs (see
[GIMPS]). Note that this NTLP SESSION ID is a different one than
the SESSION_ID associated with the end-to-end RESERVE message.
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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 messages. These are bounded together
including BOUND_SESSION_ID in the intra-domain RESERVE message.
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 if and how the
different inter domain (end-to-end) flows can be aggregated by the
QNE Ingress node (see Section 4.3.1). If no QOS-NSLP aggregation
procedure at the QNE edges is possible 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 must be sent using the NTLP datagram mode, see
Section 4.4. In addition, the intra-domain RESERVE (RMD-QSPEC)
message MUST include a PHR container (PHR_Resource_Request) and the
"RMD QOS Description" field.
The end-to-end RESERVE message includes the end-to-end QSpec and it
is sent to the Egress QNE. If the end-to-end QSpec does not carry
an RII object, then the A (Acknowledgment) flag MUST be set ON.
Otherwise the A flag MUST be set OFF.
Note that after completing the initial discovery phase, the GIMPS
connection mode can be used between the QNE Ingress and QNE Egress.
The end-to-end RESERVE message is forwarded using the GIMPS
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 NSLP-ID value
to another NSLP-ID predefined value, which corresponds to a RAO 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 [GIMPS], are configured to handle only certain
levels of router alert (RAO) values.
Furthermore, note that the initial discovery phase and the process of
sending the end-to-end RESERVE message towards the QNE Egress MAY be
accomplished simultaneously.
The (initiating) intra-domain RESERVE message MUST be used and/or
set by the QNE Ingress as follows:
* the value of the <RSN> object SHOULD be the same as the value
of the RSN object of the end-to-end RESERVE message;
* the value of the <BOUND_SESSION_ID> object MUST be the session
ID associated to the end-to-end RESERVE message;
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* the SCOPING flag SHOULD not be set, meaning that a default
scoping of the message is used. Therefore, the QNE edges MUST
be configured as boundary nodes and the QNE Interior nodes
MUST be configured as Interior (intermediary) nodes;
* The <RII> object is not included in this message;
* The flag REPLACE MUST be UNSET (set to FALSE = 0);
* the value of the <REFRESH_PERIOD> object MUST be calculated
and set by the QNE Ingress node, see also Section 4.6.1.3;
* the PHR resource units MUST be included into the <Bandwidth>
parameter of the "RMD QoS Description" field;
* the value of the Parameter/Container ID field of the PHR container
MUST be set to 1, (i.e., PHR_Resource_Request;)
* the value of the <Admitted Hops> parameter in the PHR container
MUST be set to "1";
* the value of the <Hop_U> parameter in the PHR container MUST be
set to "0";
* the flag "Acknowledge" (A) MUST be set "OFF";
* In a single-domain case the PDR container MAY not be included into
the message.
When an end-to-end RESPONSE(PDR) message is received by the QNE
Ingress node, the RMD-QSPEC, see Section 4.6.1.1.3, has to be
identified, processed and removed from the end-to-end RESPONSE
message. The QoS-NSLP state in the QNE Ingress stores and maintains
the binding between each end-to-end session and each intra-domain
session. In this way the QNE Ingress can match the PHR container that
has been carried by the intra-domain RESERVE with the received PDR
container that has been carried by the end-to-end RESPONSE message.
The RMD QoS model functionality is notified by r eading the <M>
parameter of the "PDR RMD control information" container that the
reservation has been successful.
If the end-to-end RESPONSE message has to be forwarded to a
node outside the RMD-QOSM aware domain then the non-default values of
the objects contained in this message (i.e., <RII/RSN>, <ERROR_SPEC>,
[ *QSPEC ]) MUST be used and set by the QOS-NSLP protocol functions
of the QNE.
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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:
* the values of the <RSN>, <RII>, <REFRESH_PERIOD>,
<BOUND_SESSION_ID>, <POLICY_DATA> objects are not changed,
i.e., equal to the values set by the QNE Ingress. These values
are not used by the QNE Interior;
* The flag REPLACE MUST be UNSET (set to FALSE = 0);
* the flag "Acknowledge" (A) SHOULD be set "OFF";
* the value of <Bandwidth> parameter of the "RMD QoS
Description" field is used by the QNE Interior node for
admission control, see Section 4.3.2 and Section 4.3.3;
* in case of the RMD reservation-based procedure, and if these
resources are admitted are going to be added to the currently
reserved resources per PHB and therefore they will become a
part of the per RMD traffic class (PHB) reservation state.
Furthermore, the value of the <Admitted Hops> parameter in the
PHR container has to be increased by one;
* in case of the RMD measurement based method, and if these
resources are admitted, using a MBAC algorithm, the number of
this resources will be used to update the MBAC algorithm.
4.6.1.1.3 Operation in the Egress node
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 bounded. The session included
in the <BOUND_SESSION_ID> object is the session associated with the
end-to-end RESERVE message.
The end-to-end RESERVE message 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. Otherwise the
inter domain (end-to-end) reservation is considered as being failed.
If the (A) flag carried by the end-to-end RESERVE message was set to
ON, then a one hop (end-to-end) RESPONSE message MUST be generated
by the QNE Egress. Otherwise, the QNE Egress MUST wait for the
end-to-end RESPONSE message that has the same SESSION ID as the
end-to-end RESERVE message forwarded towards QNR.
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Furthermore, the QNE Egress MUST stop the marking process that was
used to bypass the QNE Interior nodes by reassigning the QoS-NSLP
default NSLP-ID value to the end-to-end RESERVE message, see
Section 4.4.
The non-default values of the objects contained in the end-to-end
RESPONSE(PDR) message MUST be used and/or set by the QNE Egress as
follows:
* the values of the <RII/RSN>, <ERROR_SPEC> , [ *QSPEC ] objects
are set by the standard QoS-NSLP protocol functions.
In addition to the above, the QNE Egress MUST also generate a RMD-
QSPEC object that is carried by the end-to-end RESPONSE (PDR)
message, see Section 4.2.
The following parameters of the RMD-QSPEC object MUST be used and/or
set in the following way:
* the value of the Parameter/Container ID field of the PDR container
MUST be set "7" (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.
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) |
| | |------------------->|
| | | RESERVE
| | | |-->
| | | RESPONSE
| | | |<--
| |RESPONSE(PDR) | |
|<------------------------------------------------------------|
RESPONSE | | |
<---| | | |
Figure 8: Basic operation of successful reservation procedure used by
the RMD-QOSM
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The end-to-end RESPONSE(PDR) message is addressed and sent to its
upstream QoS-NSLP neighbor, i.e., QNE Ingress node. Note that for all
upstream messages the RAO is not set. Therefore, all Interior nodes
ignore the end-to-end RESPONSE messages.
4.6.1.2. Unsuccessful reservation
This section 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 the same 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
request 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.
4.6.1.2.1 Operation in the Ingress nodes
When an end-to-end RESERVE message arrives to the QNE Ingress and
if there are no resources available locally, the QNE Ingress MUST
reject this end-to-end RESERVE message and sends a RESPONSE message
back to the sender, using a standard QoS-NSLP procedure.
In 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.
In case of the RMD measurement based scenario, and if the
intra-domain reservation query (i.e., intra-domain
RESERVE(RMD-QSPEC) is not admitted by the MBAC algorithm then the
<M> parameter of the PHR container MUST be set to "1".
When an end-to-end RESPONSE(PDR) message is received by an Ingress
node, see Section 4.6.1.2.3, the following actions take place. The
non-default values of the objects contained in the end-to-end
RESPONSE (PDR) message MUST be used and/or set by the QNE Ingress
node as follows:
* the values of the <RII/RSN>, <ERROR_SPEC> ], [*QSPEC] objects
are set by standard QoS-NSLP protocol functions
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* the RMD-QSPEC object, see Section 4.2, has to be processed
and removed. The RMD Resource Management Function (RMF) is
notified by reading the <M> parameter of the PDR container that
the reservation has been unsuccessful. In case of a RMD
reservation based scenario, the RMD-QOSM functionality, has to
start an RMD release procedure (see Section 4.6.1.5).
4.6.1.2.2 Operation in the Interior nodes
In general, if a QNE Interior node receives a PHR container, of type
"PHR_Resource_Request", with the <M> parameter set to "1" then this
PHR container and the "RMD QoS Description" field MUST NOT be
Processed.
4.6.1.2.3 Operation in the Egress nodes
In the RMD reservation based and RMD measurement based scenario, 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 session included
in its BOUND_SESSION_ID object MUST be bounded. The session included
in the <BOUND_SESSION_ID> object is the session associated with the
end-to-end RESERVE.
The QNE Egress node MUST generate an end-to-end RESPONSE message
that will have to be sent to its previous stateful QoS-NSLP hop.
* the values of the <RII/RSN>, <ERROR_SPEC>, [ *QSPEC] objects
are set by the standard QoS-NSLP protocol functions;
In addition to the above, and similar to the successful operation,
see Section 4.6.1.1.3, the QNE Egress MUST also generate an RMD-QSPEC
object that is carried by the end-to-end RESPONSE message.
The following fields of the RMD-QSPEC object MUST be used and/or set
in the following way:
* the value of the <PDR Control Type> of the PDR container MUST be
set to "7" (PDR_Reservation_Report);
* the value of the <Admitted Hops> parameter of the PHR container
included in the received <M> marked PDR container MUST be included
in the <Max_Admitted Hops> parameter of the PDR container;
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* the value of the <M> parameter of the PDR container MUST be set to
"1".
QNE (Ingress) QNE (Interior) QNE (Interior) QNE (Egress)
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
RESERVE | | |
--->| | | RESERVE |
|------------------------------------------------------------>|
|RESERVE(RMD-QSPEC) | | |
|------------------->| | |
| |RESERVE(RMD-QSPEC:M =1) |
| |------------------>| |
| | | RESERVE(RMD-QSPEC:M=1)
| | |------------------->|
| |RESPONSE(PDR) | |
|<------------------------------------------------------------|
RESPONSE | | |
<---| | | |
RESERVE(RMD-QSPEC: Tear=1, M=1, <Admitted Hops>=<Max_Admitted Hops>
|------------------->| | |
Figure 9: Basic operation during unsuccessful reservation
initiation used by the RMD-QOSM
4.6.1.3 RMD refresh reservation
In case of RMD measurement-based method, QoS-NSLP states in the RMD
domain are not maintained, therefore, the end-to-end RESERVE
(refresh) message is sent directly to the QNE Egress.
The refresh procedure in case of RMD reservation-based method
follows a similar scheme as the reservation process, shown in Figure
3. If the RESERVE messages arrive within the soft state time-out
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
[QoS-NSLP]).
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. 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.
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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) 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 a "RMD QoS Description" field and a
PHR container (i.e. PHR_Refresh_Update).
The selection of the IP source and destination address of this
message depends on if and how the different inter domain
(end-to-end) flows can be aggregated by the QNE Ingress node (see
Section 4.3.1). Note that this QOS-NSLP aggregation procedure is
different than the RMD traffic class aggregation procedure. One
example is the approach used by the RSVP aggregation scenario
([RFC 3175]), where the IP source address of this message is the IP
address of the aggregator (i.e., QNE Ingress) and the IP destination
address of this message is the IP address of the De-aggregator
(i.e., QNE Egress). Another example approach is the one used
in "RSVP Refresh Overhead Reduction Extensions" ([RFC2961]). If no
QOS-NSLP aggregation procedure at the QNE edges is possible 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.
An example of this RMD specific refresh operation can be seen in
Figure 10.
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/or 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 flag "Acknowledge" (A) SHOULD be set "OFF"
* The flag REPLACE MUST be UNSET (set to FALSE = 0);
Bader, et al. [Page 25]
INTERNET-DRAFT RMD-QOSM
* the PHR resource units MUST be included into the <Bandwidth>
parameter. The value of the <Bandwidth> 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). If no QOS-NSLP aggregation is
accomplished by the QNE Ingress node, the value of the
<Bandwidth> parameter SHOULD be equal to the <Bandwidth>
parameter of its associated new (initial) intra-domain RESERVE
(RMD-QSPEC) message;
* the value of the Parameter/Container field of the "PHR RMD-QOSM
control information" container MUST be set to "2",
i.e., "PHR_Refresh_Update";
* In a single-domain case the PDR container field
MAY not be included into the message.
* the value of the <RII> object MUST contain the Response
Identification Information value of the Ingress QNE, that is
unique within a session and different for each message (see
[QoS-NSLP]).
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>, <ERROR_SPEC>, [ *QSPEC] objects
are processed by the standard QoS-NSLP protocol functions;
* the PDR has to be processed and removed 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 session(s) (in case of the flow aggregation procedure there
will be more than one sessions) associated with this RMD specific
refresh session MUST be informed about the success or failure of
the refresh procedure. In 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 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" control information 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.
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INTERNET-DRAFT RMD-QOSM
The following objects are used and/or set differently:
* the value of <Bandwidth> parameter of the "RMD QoS Description"
field is used by the QNE Interior node for refreshing the RMD
traffic class state. These resources (included in <Bandwidth>),
if reserved, are added to the currently reserved resources
per PHB and therefore they will become a part of the per traffic
class (per-PHB) reservation state. If the refresh procedure
cannot be fulfilled then the <M> parameter of the PHR container
has to be set to "1".
Any PHR container of type "PHR_Refresh_Update", and its associated
"RMD QoS Description" field (i.e., <Bandwidth>), whether it is
marked or not, 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. This
message MUST include a PDR (type PDR_Refresh_Report).
The intra-domain RESPONSE (RMD-QSPEC) message MUST be sent to the
QNE Ingress node, i.e., previous stateful hop. The address of the QNE
Ingress node can be found using the existing messaging association
between the QNE Egress and QNE Ingress nodes. This state is
associated with the end-to-end session and identified by the SESSION
ID that is bound to the session of the intra-domain
RESPONSE(RMD-QSPEC) message.
The following objects MUST be used and/or set differently:
* the value of the <PDR Control Type> parameter of the PDR container
MUST be set "8" (i.e. PDR_Refresh_Report).
4.6.1.4. RMD modification of aggregated reservations
In the case when the QNE edges maintain QoS-NSLP aggregated
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 <Bandwidth> parameter of the "RMD QoS Description"
field, 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" control information that is associated with
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INTERNET-DRAFT RMD-QOSM
the <Bandwidth> parameter MUST be marked. 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 <Bandwidth> parameter of the "RMD QoS Description" field.
Subsequently an RMD release procedure SHOULD be accomplished (see
Section 4.6.1.5).
4.6.1.5 RMD release procedure
If a refresh RESERVE message does not arrive at a QNE Interior node
within the refresh time-out period then the resources associated
with this message are removed. This soft state behavior provides
certain robustness for the system ensuring that unused resources are
not reserved for long time. Resources can be removed by explicit
release at any time.
When the RMD-RMF of a QNE edge or QNE Interior node processes a
"PHR_Release_Request" control information it MUST identify
the <PHB Class> parameter and estimate the time period that elapsed
after the previous refresh. 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. 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>
parameter of the "PHR_Release_Request" control information. When a
node (QNE edge or QNE Interior) receives the "PHR_Release_Request"
control information, it MUST store the arrival time. Then it MUST
calculate the time difference, say "Tdiff", 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.
This 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
<Bandwidth> parameter of the "RMD QoS Description" field that has
been sent together with the "PHR_Release_Request" control
information container, but not below zero.
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An RMD specific release procedure can be triggered by an end-to-end
RESERVE with a TEAR flag set 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 ON) "PDR_Reservation_Report" or
"PDR_Congestion_Report".
4.6.1.5.1. Triggered by a RESERVE message
This RMD explicit release procedure can be triggered by a tear (TEAR
flag set ON) end-to-end RESERVE message. When a tear (TEAR flag
set ON) end-to-end RESERVE message arrives to the QNE Ingress
then the QNE Ingress node SHOULD process the message in a standard
QoS-NSLP way (see [QoS-NSLP]). In addition to this, the RMD RMF
MUST be notified.
Similar to 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 NSLP-ID value to another NSLP-ID predefined value, which
corresponds to a RAO value that will be used by the GIST message that
carries the end-to-end RESPONSE message to bypass the QNE Interior
nodes. It will generate an intra-domain RESERVE(RMD-QSPEC) message.
Before generating this message, the RMD RMF is using the RMD traffic
class (PHR) resources (specified in <Bandwidth>) and the PHB type
(specified in <PHB Class>) for a RMD release procedure. This can be
achieved by subtracting the amount of the requested resources from
the total reserved amount of resources stored in the RMD traffic
class state.
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
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The intra-domain RESERVE (RMD-QSPEC) message MUST include a "RMD
QoS Description" field and a PHR container, (i.e.,
"PHR_Resource_Release") and it MAY include a PDR container, (i.e.,
PDR_Release_Request). An example of this operation can be seen in
Figure 11.
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:
* the flag "Acknowledge" (A) SHOULD be set "OFF";
* The flag REPLACE MUST be UNSET (set to FALSE = 0);
* The <RII> object is not included in this message. This is
because the QNE Ingress node does not need to receive a
response from the QNE Egress node;
* the TEAR flag is set to ON;
* the PHR resource units MUST be included into the <Bandwidth>
parameter of the "RMD QoS Description" field;
* the value of the <Admitted Hops> parameter has to be set to "1";
* the value of the <Time Lag> parameter of the PHR container is
calculated by the RMD-QOSM functionality (see 4.6.1.5)the value of
the <Control Type> parameter of PHR container is set to "3" (i.e.,
PHR_Resource_Release).
The intra-domain tear RESERVE (RMD-QSPEC) message is received and
processed by the QNE Interior nodes. Most of the non-default
values of the objects contained in this refresh intra-domain RESERVE
(RMD-QSPEC) message are set by a QNE Interior node in the same way
as described in Section 4.6.1.1. The following objects are set and
processed differently:
* Any QNE Interior node that receives the combination of the "RMD
QoS Description" field and the "PHR_Resource_Release" control
information container, it MUST identify the traffic class (PHB)
and release the requested resources included in the <Bandwidth>
parameter. This can be achieved by subtracting the amount of RMD
traffic class requested resources, included in the <Bandwidth>
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_Resource_Release" container is used during the release
procedure as explained in Section 4.6.1.5.
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The intra-domain tear RESERVE (RMD-QSPEC) message is received and
processed by the QNE Egress node. The "RMD QoS Description" and the
"PHR RMD-QOSM control " container (and if available the "PDR RMD-QOSM
control information" container) are read and processed by the RMD QoS
signaling model functionality. The value of the <Bandwidth>
parameter of the "RMD QoS Description" field and the value of the
<Time Lag> field of the PHR container MUST be used by the RMD release
procedure. This can be achieved by subtracting the amount of RMD
traffic class requested resources, included in the <Bandwidth>
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.,
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 NSLP-ID value to
the end-to-end RESERVE message, see Section 4.4.
4.6.1.5.2 Triggered by a marked RESPONSE or NOTIFY message
This RMD explicit release procedure can be triggered by either an
end-to-end RESPONSE message with a <M> marked PDR container (see
Section 4.6.1.2) an intra-domain RESPONSE message with a <S> marked
PDR container (see Section 4.6.1.6.1) or an end to end NOTIFY (PDR)
message (see Section 4.6.1.6) with a <S> marked PDR container.
This RMD specific release procedure can be terminated at any QNE edge
or any QNE Interior node using the <Max_Admitted Hops> field.
The RMD specific explicit release procedure that is terminated at a
QNE Interior (or QNE edge) node is denoted as RMD specific partial
release procedure. This explicit release procedure
can be used, for example, during a RMD specific operation for
unsuccessful reservation (see Section 4.6.1.2) or severe congestion
(see Section 4.6.1.6). When the RMD QoS signaling model
functionality of a QNE Ingress node receives a <M> or <S> marked
PDR container of type "PDR_Reservation_Report" or
"PDR_Congestion_Report", it MUST start an RMD partial release
procedure. The QNE Ingress node generates an intra-domain RESERVE
(RMD-QSPEC) message. Before generating this message, the RMD-QOSM
functionality is using the RMD traffic class (PHR) resource units for
a RMD release procedure. This can be achieved by subtracting the
amount of RMD traffic class requested resources from the total
reserved amount of resources stored in the RMD traffic class state.
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INTERNET-DRAFT RMD-QOSM
When the generation of the intra-domain RESERVE (RMD-QSPEC) message
is triggered by an end-to-end NOTIFY(PDR) message then the intra-
domain RESERVE(RMD-QSPEC) message MUST include a
<RMD QoS Description> field and a PHR container, (i.e.,
PHR_Resource_Release) and it MAY include a PDR container, (i.e.,
PDR_Release_Request). An example of this message exchange can be seen
in Figure 12.
QNE (Ingress) QNE (Interior) QNE (Interior) QNE (Egress)
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
| | | |
| NOTIFY (PDR) | | |
|<-------------------------------------------------------|
|RESERVE(RMD-QSPEC:Tear=1,M=1,S=SET) | |
| ---------------->|RESERVE(RMD-QSPEC:Tear=1, M=1,S=SET) |
| | | |
| |----------------->| |
| | RESERVE(RMD-QSPEC:Tear=1, M=1,S=SET)
| | |----------------->|
Figure 12: Basic operation during RMD explicit release procedure
triggered by NOTIFY used by the RMD-QOSM
When the generation of the intra-domain RESERVE(RMD-QSPEC) message
is triggered by an end-to-end RESPONSE(PDR) message then this
generated intra-domain RESERVE(RMD-QSPEC) message MUST include a
<RMD QoS Description> field and a PDR container, (i.e.,
PHR_Resource_Release) and it MAY include a PDR container, (i.e.,
PDR_Release_Request). 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.
The following objects MUST be used and/or set differently:
* the flag "Acknowledge" (A) SHOULD be set "OFF";
* The flag REPLACE MUST be UNSET (set to FALSE = 0);
* The value of the <M> parameter of the PHR container MUST be set
to "1".
* When the tear intra-domain RESERVE message is triggered by a
NOTIFY message, then the value of the <S> parameter of the
PHR container MUST be set to "1".
* The RESERVE message MAY include PDR container.
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INTERNET-DRAFT RMD-QOSM
* When the tear intra-domain RESERVE message is triggered by an
intra-domain RESPONSE(RMD-QSPEC) message, then the value of the
<Max Admitted Hops> parameter of the PDR container included in the
received <M> marked intra-domain RESPONSE(PDR) message MUST be
included in the <Max Admitted Hops> parameter of the PDR container
of the RESERVE message.
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, <Admitted Hops>=<Max_Admitted Hops>)
|------------------->| | |
| | | |
Figure 13: Basic operation during RMD explicit release procedure
Triggered by RESPONSE used by the RMD-QOSM
Any QNE edge or QNE Interior node that receives the
"RMD QoS Description" field and the PHR container MUST identify the
traffic class state (PHB), using the <PHB Class> parameter, and
release the requested resources included in the <Bandwidth> field.
This can be achieved by subtracting the amount of RMD traffic class
requested resources, included in the <Bandwidth> field, 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 Section 4.6.1.5.
The <Admitted Hops> value included in the PHR container is increased
by one. If the value of <M> parameter of the "PHR_Resource_Release"
control information container is "1" and if the value of the <S>
parameter is set to "0" then the <Max_Admitted Hops> value included
in the PDR container MUST be compared with the calculated <Admitted
Hops> value. When these two values are equal then the intra-domain
RESERVE(RMD-QSPEC) has to be terminated and it will not be forwarded
downstream. The reason of this is that the QNE node that is
currently processing this message was the last QNE node that
successfully processed the "RMD QoS Description" field 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>
parameter of the "PHR_Resource_Request" control information. When
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INTERNET-DRAFT RMD-QOSM
the values of the <M> and <S> parameters are set to "0", then this
message will not be terminated by a QNE Interior node, but it will be
forwarded in the downstream direction. The QNE Egress node will
receive and process the PHR_Resource_Release control information.
Afterwards, the QNE Egress node MUST terminate the intra-domain
RESERVE(RMD-QSPEC) message.
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. router or 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 re-routed traffic will follow a new
path, which may result in overloaded nodes as they need to support
more traffic than their capacity allows. 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 (proportional
marking) or marking the refresh messages using the <S> and
<Overload %> parameters.
4.6.1.6.1 Severe congestion handling by the RMD-QOSM 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
"S" marking the refresh messages and by including the percentage of
overload into the <Overload %> field in the "PHR_Refresh_Update"
container, carried by the intra-domain RESERVE message.
The intra-domain RESPONSE message that is sent by the QNE Egress
towards QNE Ingress will contain a PDR container with a
Parameter/Container ID = 10, i.e., "PDR_Congestion_Report". The
values of the <S> and <Overload %> fields of this container should
be set equal to the values of the <S> and <Overload %> fields,
respectively, carried by the PHR_Refresh_Update" container. The
flows that cannot be supported, i.e., based on the value included in
the < Overload %> parameter, are terminated, or forwarded in a lower
priority queue. The flows can be terminated by using the RMD release
procedure described in Section 4.6.1.5.
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In general, relying 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
additional functionalities.
4.6.1.6.2.1 Operation in the Interior nodes
The QNE Interior node detecting severe congestion marks data packets
passing the node.
For the severe congestion marking, two additional DSCPs SHOULD be
allocated for each traffic class. One MAY be used to indicate that
the packet passed a congested node. The other DSCP MUST be used to
indicate the degree of congestion by marking the bytes proportionally
to the degree of congestion. Note, however, that it is RECOMMENDED
that the total number of additional DSCPs within a RMD domain, needed
for severe congestion handling MUST not exceed the limit of 16. One
possible solution for reducing the number of DSCP, for example, if
one DSCP is allocated for severe congestion indication for each AF
classes, independently from dropping precedence. Assuming 4 AF
classes and 1 EF class, the number of DSCPs used for severe
congestion is 5.
4.6.1.6.2.2 Operation in the Egress nodes
The QNE Egress node applies a predefined policy to solve the severe
congestion, by selecting a number of inter-domain (end-to-end)
flows that SHOULD be terminated, or forwarded in a lower priority
queue. For these flows (sessions), the QNE Egress node generates
and sends a NOTIFY(PDR) message to the QNE Ingress node (its
upstream stateful QoS-NSLP peer) to indicate the severe congestion
in the communication path. This message MUST include a PDR container
("PDR_Reservation_Report").
The non-default values of the objects contained in the NOTIFY(PDR)
message MUST be set by the QNE Egress node as follows:
* the values of the <ERROR_SPEC> object is set by the standard
QoS-NSLP protocol functions.
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INTERNET-DRAFT RMD-QOSM
* the value of the Parameter/Container ID of the PDR container
SHOULD be set to "10" (i.e., PDR_Congestion_Report).
* The value of the <M> parameter of the PDR container MUST be set to
"1".
* The value of the <S> parameter of the PDR container MUST be set to
"1".
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., refusing
new incoming flows (sessions), terminating the affected and notified
flows (sessions), or shifting them to an alternative RMD traffic
class (PHB). Note that due to the fact that the QoS-NSLP state in the
QNE Ingress node maintains the binding between the end-to-end and
intra-domain sessions, the QNE Ingress node can associate the PDR
container to the right 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(PDR) |flow?
|<----------------|------------------|------------------|YES
|RESERVE(RMD-QSPEC:Tear=1,M=1,S=SET) | |
| --------------->|RESERVE(RMD-QSPEC:T=1, M=1,S=SET) |
| | | |
| |----------------->| |
| | RESERVE(RMD-QSPEC:Tear=1, M=1,S=SET)
| | |----------------->|
Figure: 14 RMD severe congestion handling
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4.6.1.7 Congestion notification for admission control
The congestion notification function based on data marking
can be used to implement a simple measurement-based admission control
within a Diffserv domain. In one or a few nodes along the data path
thresholds are set in the resource management function for the
traffic belonging to different PHBs. These nodes are not necessarily
NSIS aware nodes and they do not need to process NSIS messages. If
the threshold is exceeded, the data packets are marked using a DSCP
field to indicate the high load of different PHBs. The Egress node,
when receiving the S marked packets MAY block the incoming
new requests until the traffic volume decreases below the threshold.
If a new reservation is initiated during this time, it is refused by
the Edge node, which is responsible for the admission control to the
domain.
This signaling operation is shown in Figure 15. The marking procedure
of the interior nodes is the same as for the severe congestion
operation. To distinguish between congestion notification and severe
congestion, either different DSCPs are used or a policy is configured
in the Egress edge that blocking of new resource request or
termination of some flows are done.
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----------------->|
| | | |
RESERVE | | | |
------->| | | RESERVE |
|------------------------------------------------------>|
| |RESPONSE(unsuccessful) |
|<------------------------------------------------------|
RESPONSE(unsuccessful) | | |
<------| | | |
Figure: 15 Using RMD congestion notification function for admission
control
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INTERNET-DRAFT RMD-QOSM
4.6.2 Bi-directional operation
RMD assumes asymmetric routing by default. 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 bi-directional 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.
This bi-directional sender&sender procedure can then be applied
between the QNE edges (QNE Ingress and QNE Egress) nodes of the RMD
QoS signaling model. In the situation that a security association
exists between the QNE Ingress and QNE Egress nodes (see Figure 15),
and the QNE Ingress node has the required <Bandwidth> parameters
for both directions, i.e., QNE Ingress towards QNE Egress and QNE
Egress towards QNE Ingress, then the QNE Ingress MAY include both
<Bandwidth> 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
the <BOUND_SESSION_ID> object at the QNE Ingress and QNE Egress.
|------ RESERVE (QoS-1, QoS-2)----|
| V
| Interior/stateless QNEs
+---+ +---+
|------->|QNE|-----|QNE|------
| +---+ +---+ |
| V
+---+ +---+
|QNE| |QNE|
+---+ +---+
^ |
| | +---+ +---+ V
| |-------|QNE|-----|QNE|-----|
| +---+ +---+
Ingress/ Egress/
statefull QNE statefull QNE
|
<--------- RESERVE (QoS-2) -------|
Figure 16: The bi-directional reservation scenario in the RMD domain
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A bidirectional reservation, within the RMD domain, is indicated by
the PHR <B> and PDR <B> flags, which are set in all messages.
Upstream end-to-end messages include the session ID of downstream
messages using BOUND_SESSION_ID and vice versa.
If no security association exists between the QNE Ingress and QNE
Egress nodes the bi-directional reservation for the sender&sender
scenario in the RMD domain SHOULD use the scenario specified in
[QoS-NSLP] as "Bi-directional reservation for sender&sender
scenario".
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 bounded 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 <Bandwidth> parameters
for both directions, i.e., QNE Ingress towards QNE Egress and
QNE Egress towards QNE Ingress.
4.6.2.1 Successful and unsuccessful reservations
This section describes the operation of the RMD-QOSM where a RMD
bi-directional reservation operation is either successfully or
unsuccessfully accomplished.
The bi-directional successful reservation is similar to a
combination of two unidirectional successful reservations that are
accomplished in opposite directions, see Figure 16. The main
differences of the bi-directional successful reservation procedure
with the combination of two unidirectional successful reservations
accomplished in opposite directions are as follows. The intra-
domain RESERVE message sent by the QNE Ingress node towards the QNE
Egress node, is denoted in Figure 16 as RESERVE (RMD-QSPEC):
"forward". The main differences between the RESERVE (RMD-QSPEC):
"forward" message used for the bi-directional successful reservation
procedure and a RESERVE (RMD-QSPEC) message used for the
unidirectional successful reservation are as follows:
* the RII object is not included in the message. This is because no
RESPONSE message is expected to arrive.
* the <B> bit of the PHR container
indicates a bi-directional reservation and is set to "1".
Bader, et al. [Page 39]
INTERNET-DRAFT RMD-QOSM
* the PDR container is also included into the RESERVE(RMD-QSPEC):
"forward" message. The value of the Parameter/Container ID is
"4"., 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 bi-directional reservation and is set
to "1".
* the <PDR Reverse Requested Resources> 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 bi-directional successful reservation procedure
and a RESERVE(RMD-QSPEC) message used for the unidirectional
successful reservation are as follows:
* the RII object is not included in the message. This is because no
RESPONSE message is expected to arrive;
* the value of the <Bandwidth> parameter is set equal to the value
of the <PDR Reverse Requested Resources> field included in the
RESERVE(RMD-QSPEC):"forward" message that triggered the
generation of this RESERVE(RMD-QSPEC): "reverse" message;
* the value of the [BOUND_SESSION_ID] object is set equal to
the SESSION_ID of the intra domain session associated with 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 bi-directional
reservation and is set to "1";
* the PDR container is included into the
RESERVE(RMD-QSPEC):"reverse" message. The value of the
Parameter/Container ID is "7", i.e., "PDR_Reservation_Report";
* the <B> PDR bit indicates a bi-directional reservation and is
set to "1".
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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) |
| RESERVE(RMD-QSPEC) | "reverse" |<-------------|
| "reverse" | |<--------------| |
|<-------------------------------| | |
Figure 17: Intra-domain signaling operation for successful
bi-directional reservation
Figure 18 and Figure 19 show the flow diagrams used in case of a
unsuccessful bi-directional reservation. In Figure 17 it
is considered that the QNE that is not able to support the
requested <Bandwidth> is located in the direction QNE Ingress
towards QNE Egress. In Figure 19 it is considered that the
QNE that is not able to support the requested <Bandwidth> is
located in the direction QNE Egress towards QNE Ingress.
The main differences between the bi-directional unsuccessful
procedure shown in Figure 17 and the bi-directional 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., path
from QNE Ingress towards the QNE Egress.
* the QNE node that is not able to support the requested
<Bandwidth> it MUST mark the <M> bit, i.e., set to value "1", of
the RESERVE(RMD-QSPEC): "forward".
The operation for this type of unsuccessful bi-directional
reservation is similar to the operation for unsuccessful uni-
directional reservation shown in Figure 9. The main difference
is that the QNE Egress generates an intra-domain (local)
RESPONSE(PDR) message that is sent towards QNE Ingress node.
Bader, et al. [Page 41]
INTERNET-DRAFT RMD-QOSM
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) | M |
|"forward - T tear" | M |
|----------------> | M |
Figure 18: Intra-domain signaling operation for unsuccessful
bi-directional reservation (rejection on path QNE(Ingress)
towards QNE(Egress))
The main differences between the bi-directional unsuccessful
procedure shown in Figure 18 and the in bi-directional 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., path
from QNE Egress towards the QNE Ingress.
* the QNE node that is not able to support the requested
<Bandwidth> it MUST mark the <M> bit, i.e., set to value "1",
the RESERVE(RMD-QSPEC):"reverse".
* 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 (local) RESERVE(RMD-QSPEC):
"forward - T tear" message. This message carriers a
"PHR_Release_Request" and a "PDR_Release_Request" control
information. This message is sent to QNE Egress node.
The QNE Egress node by using the information contained in the
"PHR_Release_Request" and the "PDR_Release_Request" control
info containers it generates a RESERVE(RMD-QSPEC):"reverse - T
tear" message that is sent towards the QNE Ingress node.
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INTERNET-DRAFT RMD-QOSM
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): M | |
|"forward - T tear" M | |
|--------------->| RESERVE(RMD-QSPEC): | |
| | "forward - T tear" | |
| |-------------------------------->| |
| | M |------------->|
| | M RESERVE(RMD-QSPEC):
| | M reverse - T tear" |
| | M |<-------------|
Figure 19: Intra-domain signaling normal operation for unsuccessful
bi-directional reservation (rejection on path QNE(Egress)
towards QNE(Ingress)
4.6.2.2 Refresh reservations
This section describes the operation of the RMD-QOSM where a RMD
bi-directional refresh reservation operation is accomplished.
The refresh procedure in case of RMD reservation-based method
follows a similar scheme as the successful reservation procedure,
described in Section 4.6.2.1, and depicted in Figure 16 and the
way of how the refresh process of the reserved resources is
maintained, is similar to the refresh process used for the intra-
domain uni-directional reservations (see Section 4.6.1.3).
Note that the RMD traffic class refresh periods used by the bound bi-
directional 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 bi-directional refresh procedure
and a RESERVE(RMD-QSPEC):"forward" message used for the bi-
directional successful reservation procedure are as follows:
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INTERNET-DRAFT RMD-QOSM
* the value of the Parameter/Container ID of the PHR container is
"2", i.e., "PHR_Refresh_Update".
* the value of the Parameter/Container ID of the PDR container is
"5"., i.e., "PDR_Refresh_Request".
The main differences between the RESERVE(RMD-QSPEC):"reverse"
message used for the bi-directional refresh procedure and the RESERVE
(RMD-QSPEC): "reverse" message used for the bi-directional successful
reservation procedure are as follows:
* the value of the Parameter/Container ID of the PHR container is
"2", i.e., "PHR_Refresh_Update".
* the value of the Parameter/Container ID of the PDR container is
"8"., i.e., "PDR_Refresh_Report".
4.6.2.3 Modification of aggregated reservations
This section describes the operation of the RMD-QOSM where a RMD
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 <Bandwidth> parameter of the "RMD QoS Description" field,
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, then the
"PHR_Resource_Request" control information associated with the
<Bandwidth> parameter MUST be marked. In this situation the RMD
specific operation for unsuccessful reservation will be applied (see
Section 4.6.2.1).
* When the modification request requires a decrease of the
reserved resources, the QNE Ingress node MUST include this value
into the <Bandwidth> parameter of the "RMD QoS Description" field.
Subsequently an RMD release procedure SHOULD be accomplished (see
Section 4.6.2.4).
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4.6.2.4 Release procedure
This section describes the operation of the RMD-QOSM where a RMD
bi-directional 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 16. However, the way of how
the release of the reservation is accomplished, is similar to the RMD
release procedure used for the intra-domain uni-directional
reservations (see Section 4.6.1.5 and Figure 17 and Figure 18).
The main differences between the RESERVE (RMD-QSPEC):
"forward" message used for the bi-directional release procedure
and a RESERVE (RMD-QSPEC): "forward" message used for the bi-
directional successful reservation procedure are as follows:
* the value of the Parameter/Container ID of the PHR container is
"3", i.e."PHR_Release_Request";
* the value of the Parameter/Container ID of the PDR container is
"6"., i.e., "PDR_Release_Request";
The main differences between the RESERVE (RMD-QSPEC): "reverse"
message used for the bi-directional release procedure and the RESERVE
(RMD-QSPEC): "reverse" message used for the bi-directional successful
reservation procedure are as follows:
* the value of the Parameter/Container ID of the PHR container is
"3", 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 bi-directional reservation procedures.
This severe congestion handling operation is similar to the one
described in Section 4.6.1.6.
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4.6.2.5.1 Severe congestion handling by the RMD-QOSM bi-directional
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 to 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 a bi-directional
reservation procedure.
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" path (i.e.,
path between QNE Ingress towards QNE Egress) or "reverse" path (i.e.,
path between QNE Egress towards QNE Ingress).
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
bi-directional reservation (congestion on path QNE(Ingress)
towards QNE(Egress))
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Figure 20 shows the scenario where the severe congested node is
located in the "forward" path. 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.
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
| | | | |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
bi-directional reservation (congestion on path QNE(Egress)
towards QNE(Ingress))
Figure 21 shows the scenario where the severe congested node is
located in the "reverse" path. The main difference between this
scenario and the scenario shown in Figure 20 is that no intra-domain
NOTIFY(PDR) message has to be generated by the QNE Egress node. This
is because the (#marked and #unmarked) user data is arriving at the
QNE Ingress. 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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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.
4.6.2.5.3 Congestion notification for admission control
This section describes the congestion notification function used for
admission control when bi-directional reservations are supported.
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 where the severe congested node is
located in the "forward" path. The Egress node, when receiving the S
marked packets, MAY block the incoming new requests until the traffic
volume decreases below the threshold. If a new reservation is
initiated during this time, it is refused by the Edge node, which is
responsible for the admission control to the domain. Note that the
last part of the diagram (when sending the RESERVE in forward
direction) is similar to the scenario described in Section 4.6.2.1,
Figure 18.
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 |
|-------------------------------------------->S (#marked bytes)
| | | S-------------->|
| | | S(#unmarked bytes)
| | | S-------------->|
| | | S |
| | RESERVE(RMD-QSPEC): |
| | | "forward" S |
|------------------------------------------------------------>|
| | | S |
| | RESPONSE(PDR) S |
| | "forward - M marked"S |
|<------------------------------------------------------------|
Figure 22: Intra-domain RMD congestion notification for
bi-directional admission control (congestion on path
QNE(Ingress) towards QNE(Egress))
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Figure 23 shows the scenario where the congested node is
located in the "reverse" path. The main difference between this
scenario and the scenario shown in Figure 22 is that no NSIS
signaling is used, by the QNE ingress. The QNE ingress is notified
already, by the user data packets that a congestion occurred in the
network and therefore it is able to refuse new initiation of
reservations that had to be initiated during this time.
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 | | |
Figure 23: Intra-domain RMD congestion notification for
bi-directional 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
of how these additional errors are handled and notified is specified
in [QSP-T].
5. Security Considerations
A router implementing a QoS signaling protocol can, similar to a
router without QoS signaling, do a lot of harm to a system. A router
can delay, drop, inject, duplicate or modify packets. Additional
threats are, however, introduced with new protocols and they are
subject for a discussion below.
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The RMD QOSM aims to be very lightweight signaling with regard to
the number of signaling message roundtrips and the amount of state
established at involved signaling nodes with and without reduced
state on QNEs. This implies the usage of the Datagram Mode which
does not allow channel security to be used. As such, RMD signaling is
targeted towards intra-domain signaling only.
In the context of RMD QOSM signaling a classification between
on-path adversaries and off-path adversaries needs to be made.
Furthermore, it might be necessary to differentiate between off-path
nodes that never participate in the RMD signaling exchange and nodes
that are only off-path with regard to a specific signaling session
whereby routing asymmetry might even mean that the downstream and the
upstream signaling direction matters for this classification.
Note 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 E2E signaling exchange then the RESERVE message
is created by a node outside the RMD domain and will subsequently
travel further on (e.g., to the data receiver). Such an exchange is
shown in Figure 3. As such, an evaluation of RMD's security must
always been seen as a combination of the two signaling sessions, (1)
and (2) of Figure 24.
QNE QNE QNE QNE
Ingress Interior Interior Egress
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
| | | |
| RESERVE (1) | | |
+--------------------------------------------->|
| RESERVE' (2) | | |
+-------------->| | |
| | RESERVE' | |
| +-------------->| |
| | | RESERVE' |
| | +------------->|
| | | |
| | | |
| | | |
| | | |
| | | RESPONSE (1) |
|<---------------------------------------------+
| | | |
| | | |
Figure 24: RMD message exchange
The following security requirements are set as goals for the
intra-domain communication, namely:
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INTERNET-DRAFT RMD-QOSM
* Nodes, which are never supposed to participate in the NSIS signaling
exchange, SHOULD NOT interfere with QNE Interior nodes. Off-path
nodes (off-path with regard to the path taken by a particular
signaling message exchange) SHOULD 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.
If we assume that the RESERVE/RESPONSE is sent in C-Mode and
protected between the QNE Ingress and the QNE Egress node then we can
be sure that the payloads of these messages MUST be authenticated,
integrity, replay protected and encrypted. Encryption is necessary to
prevent an adversary that is located along the path of the RESERVE
message to learn information about the session that can later be used
to inject a valid RESERVE'. The following messages need to relate to
each other to make sure that the occurrence of one message is not
without the other one:
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' (carried in the RESPONSE) relate to
each other
The RESERVE and the RESERVE' message are tied together using the
BOUND_SESSION_ID. 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 re-routing
or due to mobility) then an adversary could inject RESERVE' messages
(with a previously seen SESSION_ID) and could potentially cause harm.
[Editor's Note: We will deal with this issue in the later version
of the document.]
Bader, et al. [Page 51]
INTERNET-DRAFT RMD-QOSM
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.
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
<Overload %> 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 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'.
QNE QNE QNE QNE
Ingress Interior Interior Egress
NTLP stateful NTLP stateless NTLP stateless NTLP stateful
| | | |
| REFRESH | | |
| RESERVE' | | |
+-------------->| REFRESH | |
| (+RII) | RESERVE' | |
| +-------------->| REFRESH |
| | (+RII) | RESERVE' |
| | +------------->|
| | | (+RII) |
| | | |
| | | |
| | | REFRESH |
| | | RESPONSE'|
|<---------------------------------------------+
| | | (+RII) |
| | | |
Figure 25: RMD REFRESH message exchange
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'
(as a refresh) was created by the QNE Ingress node since the
BOUND_SESSION_ID is included in the RESERVE' message.
Bader, et al. [Page 52]
INTERNET-DRAFT RMD-QOSM
With the initial RESERVE'/RESERVE exchange there is a one-to-one
mapping between the RESERVE and the RESERVE' message based on the
SESSION_ID that is used in the two messages and the BOUND_SESSION_ID.
With the REFRESH' message this is not the case since they relate to
one RESERVE message exchange.
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. 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/re-routing case
where the path through the network changes and the set of nodes that
are along a path changes over time.
6. IANA Considerations
RMD-QOSM requires a new IANA registry.
7. Open issues
This section describes the open issues related to the RMD QoS
signaling model.
8. 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, D. Partain, M.
Jacobsson, S. Oosthoek, P. Wallentin, P. Goering, A. Stienstra, M.
de Kogel,M. Zoumaro-djayoon, M. Swanink.
Bader, et al. [Page 53]
INTERNET-DRAFT RMD-QOSM
9. 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
Siemens AG
Siemensdamm 62
Berlin 13627, Germany
Email: cornelia.kappler@siemens.com
Hannes Tschofenig
Siemens AG
Otto-Hahn-Ring 6
Munich 81739, Germany
EMail: Hannes.Tschofenig@siemens.com
Tom Phelan
Sonus Networks
250 Apollo Dr.
Chelmsford, MA USA 01824
EMail: tphelan@sonusnet.com
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
Bader, et al. [Page 54]
INTERNET-DRAFT RMD-QOSM
10. Normative References
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[QoS-NSLP] Bosch, S., Karagiannis, G. and A. McDonald, "NSLP for
Quality-of-Service signaling", draft-ietf-nsis-qos-nslp-06 (work
in progress), July 2005.
[QSP-T] Ash, J., Bader, A., Kappler C., "QoS-NSLP QSpec Template"
draft-ietf-nsis-QSpec-05 (work in progress), July 2005.
11. Informative References
[RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, A., Jamin, S.,
"Resource ReSerVation Protocol (RSVP)-- Version 1 Functional
Specification", IETF RFC 2205, 1997.
[RFC2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.
and S. Molendini, "RSVP Refresh Overhead Reduction Extensions",
RFC 2961, April 2001.
[RFC3175] Baker, F., Iturralde, C. Le Faucher, F., Davie, B.,
"Aggregation of RSVP for IPv4 and IPv6 Reservations",
IETF RFC 3175, 2001.
[GIMPS] Schulzrinne, H., Hancock, R., "GIST: General Internet
Messaging Protocol for Signaling", draft-ietf-nsis-ntlp-05
(work in progress), Oct 2004.
[RFC1633] Braden R., Clark D., Shenker S., "Integrated Services in
the Internet Architecture: an Overview", RFC 1633
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.
and W. Weiss, "An Architecture for Differentiated Services", RFC
2475, December 1998
[RFC2638] Nichols K., Jacobson V., Zhang L. "A Two-bit
Differentiated Services Architecture for the Internet", RFC 2638,
July 1999
[RMD1] Westberg, L., et al., "Resource Management in Diffserv
(RMD): A Functionality and Performance Behavior Overview", IFIP
PFHSN'02
[RMD2] G. Karagiannis, et al., "RMD - a lightweight application
of NSIS" Networks 2004, Vienna, Austria.
Bader, et al. [Page 55]
INTERNET-DRAFT RMD-QOSM
[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
[RSVP-DOI] Tschofenig H., Schulzrinne H., "RSVP Domain of
Interpretation for ISAKMP ", draft-tschofenig-rsvp-doi-00.txt,
(work in progress), May 2003
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Bader, et al. [Page 56]
