NSIS Working Group Attila Bader
INTERNET-DRAFT Lars Westberg
Ericsson
Expires: November 2005 Georgios Karagiannis
University of Twente
Cornelia Kappler
Siemens
Tom Phelan
Sonus
May 15, 2005
RMD-QOSM - The Resource Management in Diffserv QOS Model
<draft-ietf-nsis-rmd-02.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. RMD complements the Diffserv architecture by pushing
complex classification, conditioning and admission control functions
to the edges of a Diffserv domain and simplifying the operation of
internal nodes. The RMD QoS Model allows devices external to the
RMD network to signal reservation requests to edge nodes in the RMD
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network. The RMD ingress edge nodes classify the incoming flows into
traffic classes and signals resource requests for the corresponding
traffic class along the data path to the egress edge nodes for each
flow. Egress nodes reconstitute the original requests and continue
forwarding them along the data path towards the final destination.
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 . . . . . . . . . . . . .8
4.1.2 PHR RMD-QOSM control information . . . . . . . . . 8
4.1.3 PDR RMD-QOSM control information . . . . . . . . 10
4.1.4 Mapping of QSpec parameters onto generic
QSpec Parameters . . . . . . . . . . . . . . . . .12
4.2 Message format . . . . . . . . . . . . . . . . . . . . .12
4.3 RMD node state management . . . . . . . . . . . . . . . 13
4.3.1 Aggregated versus per flow reservations at the
QNE edges . . . . . . . . . . . . . . . . . . . . 13
4.3.2 Measurement-based method . . . . . . . . . . . . .14
4.3.3 Reservation-based method . .. . . . . . . . . . . 14
4.4 Transport of RMD-QOSM messages . . . . . . . . . . . . .15
4.5 Edge discovery and addressing of messages . . . . . . . 15
4.6 Operation and sequence of events . . . . . . . . . . . .15
4.6.1 Basic unidirectional operation . . . . . . . . . .17
4.6.1.1 Successful reservation. . . . . . . . . . . .17
4.6.1.2 Unsuccessful reservation . . . . . . . . . . 20
4.6.1.3 RMD refresh reservation. . . . . . . . . . . 22
4.6.1.4 RMD modification of aggregated reservation . 26
4.6.1.5 RMD release procedure. . . . . . . . . . . . 26
4.6.1.6 Severe congestion handling . . . . . . . . .34
4.6.2 Bidirectional operation . . . . . . . . . . . . . 34
4.6.2.1 Successful and unsuccessful reservation . . .36
4.7 Handling of additional errors . . . . . . . . . . . . . 39
5. Security Consideration. . . . . . . . . . . . . . . . . . . 39
6. IANA Considerations. . . . . . . . . . . . . . . . . . . . .41
7. Open issues. . . . . . . . . . . . . . . . . . . . . . . . .41
7.1 Explicit congestion notification . . . . . . . . . . . .41
7.2 Bidirectional severe congestion handling . . . . . . . .41
7.2 QoS-NSLP objects required for security considerations. .41
8. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . .41
9. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . 42
10. Normative References . . . . . . . . . . . . . . . . . . . 42
11. Informative References . . . . . . . . . . . . . . . . . . 43
12. Intellectual Property Rights . . . . . . . . . . . . . . . 44
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1. Introduction
This document describes a Next Steps In Signaling (NSIS) QoS model
for networks that use the Resource Management in Diffserv (RMD)
framework ([RMD1], [RMD2], [RMD3]). RMD adds admission control to
Diffserv networks and allows nodes external to the networks to
dynamically reserve resources within the Diffserv domains. 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 is able to terminate the
appropriate number of flows in case a of congestion due to a
sudden failure (e.g., link, router) within the domain.
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-NSLP service in an RMD network.
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 internal nodes but per flow signaling is performed (see
[QoS-NSLP]).
In the RMD-QOSM, only routers at the edges of a Diffserv domain
support the QoS-NSLP stateful operation. Internal routers support
either the QoS-NSLP stateless operation, or a reduced-state
operation with coarser granularity than the edge nodes.
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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
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.
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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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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 1. 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).
|------| |-------| |------| |------|
| 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 1: Protocol model of stateless/reduced state 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 severe congestion
operation (see Section 4.6.1.6).
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3.2.2 RMD-QOSM signaling
The basic RMD-QOSM signaling is shown in Figure 2. 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.
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 2: Sender-initiated reservation with Reduced State Interior
Nodes
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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" and the Per Domain Reservation "PDR RMD-QOSM control
information". The "RMD-QOSM QoS Description" and the "PHR RMD-QOSM
control information" fields are used and processed by edge and
interior nodes. The "PDR RMD-QOSM control information" field is
only processed by edge nodes. The "PHR RMD-QOSM control
information" field contains the QoS specific control
information for intra-domain communication and reservation. The
"PDR RMD-QOSM control information" 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>
4.1.2. PHR RMD-QOSM control information
This section describes the parameters used by the "PHR RMD-QOSM
control information" field.
<PHR RMD-QOSM control information> = <PHR Type> <Control Type>
<S> <Overload %> <M> <QOSM Hops> <Hop_U> <B> <Time Lag>
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<PHR Type>:
4-bit field. This specifies the per hop reservation type.
For the reservation based RMD, the value MUST be 1. For the
measurement based PHR this value MUST be 2.
<Control Type>:
4 bit field, indicating the "PHR RMD-QOSM control information"
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" (Control Type = 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" (Control Type = 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" (Control Type = 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.
<QOSM Hops>:
8 bit field. The <QOSM Hops> counts the number of hops in the RMD
domain where the reservation was successful. The <QOSM Hops>is set
to zero when a RESERVE message enters a domain and increased by one
at each interior QNE. However when a QNE is reached that does not
have sufficient resources to admit the reservation, the M Bit is
set, and the <QOSM Hops> value is frozen.
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<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 will
not increase the <QOSM 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 <QOSM 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
This section describes the parameters of the "PDR RMD-QOSM
control information" field.
<PDR type>:
4-bit field identifying the per domain reservation type.
<PDR Control Type>:
4-bit field identifying the type of "PDR RMD-QOSM control
information" field.
"PDR_Reservation_Request" (Control Type = 1): 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" (Control Type = 2): 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" (Control Type = 3): generated and sent
by the QNE(ingress) node to the QNE(egress) node to release
the per domain reservation states explicitly
"PDR_Reservation_Report" (Control Type = 4): 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" (Control Type = 5) 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
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"PDR_Release_Report" (Control Type = 6) 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" (Control Type = 7): generated and sent
by theQNE(egress) node to the QNE(ingress) node and used for Severe
congestion notification
<PDR S> (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.
<PDR_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.
<PDR M> (Marked):
1-bit. Carries the <M> value of the "PHR_Resource_Request" or
"PHR_Refresh_Update" control information fields.
<PDR B>: 1 bit Indicates bi-directional reservation.
<Max QOSM Hops>:
8-bit. The < QOSM Hops> value that has been carried by the
"PHR RMD control information" field used to identify the RMD
reservation based node that admitted or process a
"PHR_Resource_Request"
<EP-Type>:
4-bit. Identifies the used external protocol (External
Protocol Type). If the external protocol is a QoS-NSLP then
this parameter carries the QoS-NSLP protocol ID. Only useful
when the intra-domain signaling procedures are used in
combination with non-QoS-NSLP end-to-end signaling
procedures. Every edge node MUST be configured to process the
EP-Type.
<PDR Reverse Requested Resources>
16 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.
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<PDR BOUND_SESSION_ID>
128 bits. This parameter has the same format as the
BOUND_SESSION_ID object specified in [QoS-NSLP]. It represents
the SESSION_ID as specified in GIMPS of the intra domain
session that is bounded to the inter domain (end-to-end) session.
<PDR NONCE> This parameter has the same format and value as the
RII object specified in [QoS-NSLP]. An identifier that must be
unique within the context of a SESSION_ID,
and SHOULD be different every time an end-to-end RESPONSE that
carries a QSpec is desired. Used for security considerations.
Note that this parameter might be redefined in the next version
of this draft.
4.1.4. Mapping of generic parameters onto RMD QSP parameters
To be provided in a future version of this draft.
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.
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The format of a local (intra-domain) RESPONSE message used by
the RMD-QOSM is as follows:
RESPONSE = COMMON_HEADER
[ RII / RSN ] ERROR_SPEC
[ RMD-QSPEC ]
The format of an end-to-end RESPONSE message that is used by the
RMD-QOSM to carry the PDR RMD control information of
the RMD-QSPEC 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 the 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 per aggregated QoS-
NSLP reservation states then these states will 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 [RFC3175]. 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
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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).
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 do 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. In either case, the node then forwards the RESERVE
along the path towards the destination. REFRESH and RELEASE
messages are not normally generated in the measurement-based mode,
but if received SHOULD not be processed and forwarded unchanged.
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.
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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.
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,
* do not create a message association state
* do not create a reverse path routing state.
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 mode (C). 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
GIMPS datagram (D) mode. RMD QoS signaling messages addressed to
the end node are intercepted and terminated by the egress node.
4.6. Operation and sequence of events
This section describes the operation and the sequence of events in
the RMD-QOSM.
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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 and Severe congestion.
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]. 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.
4.6.1.1.1. Operation in ingress node
When an end-to-end reservation request (RESERVE) arrives at the
ingress node (QNE), it is processed based on the procedures defined
by the end-to-end QoS model. Subsequently, the QoS Description of
the end-to-end QSpec is transformed into the RMD QoS Description:
<Bandwidth> and <PHB-CLASS>, which form the RMD QoS Description.
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.
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 and it MUST be addressed to the same IP
destination as the end-to-end RESERVE message and be sent using NTLP
datagram mode. In addition, the intra-domain RESERVE (RMD-QSPEC)
message MUST include a "PHR RMD control information"
(PHR_Resource_Request) and the "RMD QOS Description" fields.
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 between the QNE
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ingress and QNE egress can be used. The end-to-end RESERVE message
is forwarded using the GIMPS bypass forwarding procedure to bypass
the interior stateless or reduced-state QNE nodes, see Figure 3.
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.
* 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 value of the <REFRESH_PERIOD> object MUST be calculated
and set by the QNE ingress node.
* the PHR resource units MUST be included into the <Bandwidth>
parameter of the "RMD QoS Description" field.
* the value of the <Control Type> "parameter of the "PHR RMD
control information" field object MUST be set to 1, (i.e.,
PHR_Resource_Request)
* the value of the <QOSM Hops> parameter in the "PHR RMD control
information" MUST be set to "1".
* the value of the <Hop_U>parameter in the "PHR RMD control
information" MUST be set to "0".
* the flag "Acknowledge" (A) MUST be set "OFF"
* <To be redefined>
the value of the <PDR NONCE> MUST contain the Response
Identification Information value of the ingress QNE, that is
unique within a session and different for each message. This
field is used for security considerations and its use will be
specified in the next version of the draft.
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:
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* 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 "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;
* 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 <QOSM Hops> parameter in the
"PHR RMD control information" field 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 the binding 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 accomplished. 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.
The QNE egress MUST then include a "PDR RMD control information"
field (i.e., PDR_Reservation_Report) into this end-to-end RESPONSE
message. Note that for all upstream messages the RAO is not set.
Therefore, all interior nodes ignore the end-to-end Response
messages. The end-to-end RESPONSE (PDR) message is sent to its
upstream QoS-NSLP neighbor. Note that this message uses
NTLP/GIMPS connection mode.
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INTERNET-DRAFT RMD-QOSM
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 3: Basic operation of successful reservation procedure used by
the RMD-QOSM
The non-default values of the objects contained in the end-to-end
RESPONSE message MUST be used and/or set by the QNE egress as
follows:
* the values of the <RII/RSN>, <ERROR_SPEC> , [ *QSPEC ] objects
are set by the standard QoS-NSLP protocol functions;
* the value of the <PDR Control Type> parameter of the "PDR RMD
control information" field MUST be set to 4 (i.e.,
PDR_Reservation_Report);
* the value of the <EP-Type> parameter of the "PDR RMD control
information" field MUST be equal to the QoS-NSLP protocol ID;
* the value of the <PDR BOUND_SESSION_ID> of the "PDR RMD
control information" field MUST be equal to the SESSION_ID
of the bound intra-domain RMD session.
* <To be redefined >
the value of the <PDR NONCE> of the "PDR RMD
control information" field MUST be equal to the <PDR NONCE>
value carried by the intra-domain RESERVE(RMD-QSPEC) message
belonging to the bound intra-domain RMD session.
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This end-to-end RESPONSE(PDR) message is received by the QNE
ingress node. If the end-to-end RESPONSE message is forwarded to a
node outside the RMD-QOSM aware domain the non-default values of the
objects contained in this message MUST be used and set by the QNE
ingress node as follows:
* the values of the <RII/RSN>, <ERROR_SPEC>, [ *QSPEC ] objects
are set by the standard QoS-NSLP protocol functions;
* the "PDR RMD control information" field has to be processed
and removed by the RMD-QOSM functionality in
the QNE ingress node. The RMD QoS model functionality is
notified by reading the <PDR M> parameter of the "PDR RMD
control information" that the reservation has been successful.
The value of the received <PDR NONCE> is used for security
considerations and its operation will be specified in the next
version of the draft.
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.
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 RMD control
information" MUST be set to "1". The <QOSM 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 used at
the QNE node, then the <M> parameter of the "PHR RMD control
information" field MUST be set to "1".
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In general, if a QNE interior node receives a "PHR RMD control
information" field, of type "PHR_Resource_Request", with the <M>
parameter set to "1" then this "PHR RMD control information" and the
"RMD QoS Description" fields MUST NOT be processed, i.e., their
parameters will neither be read nor modified. 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 4) a binding 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
accomplished. 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.
This message MUST include a "PDR RMD control information" field (of
type PDR_Reservation_Report). 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 node as follows:
* the values of the <RII/RSN>, <ERROR_SPEC>, [ *QSPEC] objects
are set by the standard QoS-NSLP protocol functions;
* the value of the <PDR Control Type> field of the "PDR RMD control
information" field MUST be set to "4" (PDR_Reservation_Report);
* the value of the <QOSM Hops> parameter of the "PHR RMD control
information" field included in the received <M> marked intra-
domain RESERVE (RMD-QSPEC) message MUST be included in the
<Max_QOSM Hops> parameter of the "PDR RMD control information"
field;
* the value of the <PDR M> parameter of the "PDR RMD control
information" field MUST be set to "1";
* the value of the <EP-Type> parameter of the "PDR RMD control
information" field MUST be equal to the QoS-NSLP protocol ID;
* the value of the <PDR BOUND_SESSION_ID> of the "PDR RMD
control information" field MUST be equal to the SESSION_ID
of the bounded intra-domain RMD session.
* <To be redefined >
the value of the <PDR NONCE> of the "PDR RMD
control information" field MUST be equal to the <PDR NONCE>
value carried by the intra-domain RESERVE(RMD-QSPEC) message
belonging to the bound intra-domain RMD session.
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, which receives this message, as follows:
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INTERNET-DRAFT RMD-QOSM
* the values of the <RII/RSN>, <ERROR_SPEC> ], [*QSPEC] objects
are set by standard QoS-NSLP protocol functions;
* the PDR object has to be processed and removed by the RMD QoS
signaling model functionality in the QNE ingress node. The
RMD QoS model functionality is notified by reading the <PDR M>
parameter of the "PDR RMD control information" 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).
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, <QOSM Hops>=<Max_QOSM Hops>) |
|------------------->| | |
Figure 4: 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 transmissions 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]).
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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.
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. This intra-domain RESERVE
(RMD-QSPEC) message MUST include a "RMD QoS Description" field and a
"PHR control information" field (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
([RFC3175]), 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 approach used
in "RSVP Refresh Overhead Reduction Extensions" ([RFC2961]). If no
QOS-NSLP aggregation procedure at the QNE edges is possible then the
IP destination address of this message MUST be equal to the IP
destination address of its associated end-to-end RESERVE message.
An example of this RMD specific refresh operation can be seen in
Figure 5.
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 5: 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"
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* 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, then 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 <Control Type> parameter of the "PHR RMD control
information" field MUST be set to "2" (i.e., PHR_Refresh_Update);
* In a single-domain case the "PDR RMD control information" 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]).
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.
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 RMD
control information" has to be set to "1".
Any "PHR RMD control information" 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.
The intra-domain RESERVE (RMD-QSPEC) message is received and
processed by the QNE egress node. A new intra-domain RESPONSE (PDR)
message is generated by the QNE egress node. This message MUST
include a "PDR RMD control information" (type PDR_Refresh_Report).
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This intra-domain RESPONSE (PDR) 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 messaging
association state is associated with the end-to-end session and it
is identified by the SESSION ID that is bound to the session
associated with the intra-domain RESPONSE (PDR) message.
The following objects MUST be used and/or set differently:
* the value of the <RII> object is equal to the value of the RII
that is used by the QNE ingress to identify the RESPONSE when
it passes back through it. This value was carried by the
intra-domain RESERVE (RMD-QSPEC) message in the <RII> object;
* the value of the <PDR Control Type> parameter of the "PDR RMD
control information" MUST be set "5" (i.e., PDR_Refresh_Report);
* the value of the <PDR M> field of the "PDR RMD control
information" MUST be equal to the value of the <M> parameter
of the "PHR RMD control information" that was carried by its
associated intra-domain RESERVE (RMD-QSPEC) message.
* the value of the <PDR BOUND_SESSION_ID> of the "PDR RMD
control information" field MUST be equal to the SESSION_ID
of the bounded intra-domain RMD session.
When the intra-domain RESPONSE (PDR) message 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 RMD control information" has to be processed and
removed by the RMD-QOSM functionality in the
QNE ingress node. The RMD-QOSM functionality
is notified by reading the <PDR M> parameter of the "PDR RMD
control information" 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.
Bader, et al. [Page 25]
INTERNET-DRAFT RMD-QOSM
4.6.1.4. RMD modification of aggregated reservations
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) 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 field. 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 field that is associated
with the <Bandwidth> parameter MUST be marked. In this situation
the RMD specific operation for unsuccessful reservation will be
applied (see Section 4.6.1.2).
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 procedure at any time.
When the RMD-RMF of a QNE edge or QNE interior node processes a
"PHR_Release_Request" control information field 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 field by the QNE
Ingress node. The value of "T_Lag" is first normalized to the
length of the refresh period, say "T_period". In other words, 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 field. When a node (QNE edge or QNE interior) receives
the "PHR_Release_Request" control information, it MUST store its
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 time lag "T_Lag", from the <Time Lag> parameter.
Bader, et al. [Page 26]
INTERNET-DRAFT RMD-QOSM
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 field, but not below zero.
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 a RESPONSE or NOTIFY message that includes a
marked (i.e., <PDR M> and/or <PDR S> parameters are set ON)
"PDR_Reservation_Report" control information field or
"PDR_Congestion_Report" control information field.
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 QoS
signaling model functionality MUST be notified. It will generate an
intra-domain RESERVE (RMD-QSPEC) message. Before generating this
message, the RMD QoS model functionality 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 6: Explicit release triggered by RESERVE used by the RMD-QOSM
Bader, et al. [Page 27]
INTERNET-DRAFT RMD-QOSM
This intra-domain RESERVE (RMD-QSPEC) message MUST include a "RMD
QoS Description" field and a "PHR RMD control information" field,
(i.e., "PHR_Resource_Release") and it MAY include a "PDR RMD control
information" field, (i.e., PDR_Release_Request). An example of this
operation can be seen in Figure 6.
The 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 <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 <QOSM Hops> parameter has to be set to one;
* the value of the <Time Lag> parameter of the "PHR RMD control
information" is calculated by the RMD-QOSM
functionality (see introductory part of Section 4.6.1.5)
the value of the <Control Type> parameter of "PHR RMD control
information" 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. The 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 field, it MUST identify the traffic class state (PHB)
(specified in <PHB-CLASS>) 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"
control information field is used during the release procedure as
explained in the introductory part of Section 4.6.1.5
Bader, et al. [Page 28]
INTERNET-DRAFT RMD-QOSM
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 control field" (and if available the "PDR RMD control
information" field) 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 RMD QoS control information" field 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.
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 (PDR) message with a <PDR M> marked "PDR RMD
control information" field (see Section 4.6.1.2) or an intra-domain
NOTIFY (PDR) message (see Section 4.6.1.6) with a <M> or <S> marked
"PDR RMD control information" field. This RMD specific release
procedure can be terminated at any QNE edge or any QNE interior
node. This is determined using the <Max_QOSM 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, for example, used 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 RMD control information" field 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.
When the generation of the intra-domain RESERVE (RMD-QSPEC) message
is triggered by an intra-domain NOTIFY (PDR) message then the
intra-domain RESERVE (RMD-QSPEC) message MUST include a
<RMD QoS Description> field and a <PHR RMD control information>
field, (i.e., PHR_Resource_Release) and a "PDR RMD control
information field", (i.e., PDR_Release_Request). An example of this
message exchange can be seen in Figure 7.
Bader, et al. [Page 29]
INTERNET-DRAFT RMD-QOSM
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 7: 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 RMD control information"
field, (i.e., PHR_Resource_Release) and a "PDR RMD control
information field", (i.e., PDR_Release_Request). An example of
this operation can be seen in Figure 8.
The 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 value of the <M> parameter of the "PHR RMD control
information" 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 RMD control information" field MUST be set to "1". The
RESERVE message SHOULD include "PDR RMD control information".
* When the tear intra-domain RESERVE message is triggered by a
RESPONSE (PDR) message, then the value of the <Max QOSM Hops>
parameter of the "PDR RMD control information" field included in
the received <M> marked intra-domain RESPONSE (PDR) message MUST
be included in the <Max QOSM Hops> parameter of the "PDR RMD
control information" field of the RESERVE message. The value of
the EP-Type parameter of the PDR message SHOULD be equal to the
QoS-NSLP protocol ID.
* When the generation of the intra-domain RESERVE (RMD-QSPEC)
message is triggered by a NOTIFY (PDR) message then this
generated intra-domain RESERVE (RMD-QSPEC) message SHOULD not
include a "PDR RMD control information" field.
Bader, et al. [Page 30]
INTERNET-DRAFT RMD-QOSM
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, <QOSM Hops>=<Max_QOSM Hops>)|
|------------------->| | |
| | | |
Figure 8: Basic operation during RMD explicit release procedure
Triggered by RESPONSE used by the RMD-QOSM
Any QNE edge or QNE interior node that receives a combination of the
"RMD QoS Description" field and the "PHR_Resource_Release" control
information field it 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 RMD control information" field is
used during the release procedure as explained in the introductory
part of Section 4.6.1.5. Furthermore, the <QOSM Hops> value included
in the "PHR RMD control information" field is increased by one. If
the value of <M> parameter of the "PHR_Resource_Release" control
information field is "1" and if the value of the <S> parameter is
set to "0" then the <Max_QOSM Hops> value included in the "PDR RMD
control information" field MUST be compared with the calculated
<QOSM 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" and "PHR RMD
control information" fields 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, and therefore this QNE node marked the
<M> parameter of the "PHR_Resource_Request" control information
field. When 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 field. Afterwards, the QNE egress node MUST
terminate the intra-domain RESERVE (RMD-QSPEC) object.
Bader, et al. [Page 31]
INTERNET-DRAFT RMD-QOSM
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 failure 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 a severe congestion occurrence
in the communication path.
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 %> RMD parameter. 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.
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
When severe congestion occurs, the re-routed traffic follows a
new path. In this situation the available resources, may not be
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. In this
version of this draft the severe congestion handling that uses the
proportional data marking is explained.
The QNE Interior node detecting severe congestion marks data packets
passing the node in which the severe congestion was detected.
For the severe congestion marking, two 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.
Bader, et al. [Page 32]
INTERNET-DRAFT RMD-QOSM
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 RMD
control information" field ("PDR_Reservation_Report"). The value of
the <PDR BOUND_SESSION_ID> parameter of the "PDR_Reservation_Report"
control information field MUST be the same as the SESSION_ID of the
flow that has to be terminated. Note that this message SHOULD use a
NTLP/GIMPS connection mode.
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.
* the value of the <PDR Control Type> parameter of the "PDR RMD
control information" field object SHOULD be set to "7" (i.e.,
PDR_Congestion_Report).
* The value of the <PDR M> parameter of the "PDR RMD control
information" field MUST be set to "1".
* The value of the <PDR S> parameter of the "PDR RMD control
information" field MUST be set to "SET".
* the value of the <PDR BOUND_SESSION_ID> parameter of the
"PDR_Reservation_Report" control information field MUST be the
same as the SESSION_ID of the flow that has to be terminated.
* the value of the EP-Type field of the "PDR RMD control
information" field MUST be the QoS-NSLP protocol ID.
Upon receiving this 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). An example of such an operation is depicted in Fig. 9.
The severe congestion notification function of RMD can be used for
implementing a simple feedback-based admission control within a
Diffserv domain. In one or a few nodes along the data thresholds
are set in the resource management function for the data traffic
belonging to different PHBs. If the threshold is exceeded the data
packets are marked in the DSCP field to indicate the high load of
different PHBs. In this case the egress node sends a NOTIFY(PDR)
message to the ingress node, which MAY block the incoming traffic
belonging to the same PHB until the traffic volume decreases below
the threshold, or forwards it in a lower priority queue.
Bader, et al. [Page 33]
INTERNET-DRAFT RMD-QOSM
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: 9 RMD severe congestion handling
4.6.2 Bi-directional operation
RMD assumes asymmetric routing by default. Combined sender-receiver
initiated reservation cannot be 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 10),
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.
Bader, et al. [Page 34]
INTERNET-DRAFT RMD-QOSM
|------ 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 10: The bi-directional reservation scenario in the RMD domain
A bidirectional reservation, within the RMD domain, is indicated by
the <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.
In the situation that 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".
Note that 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.
Bader, et al. [Page 35]
INTERNET-DRAFT RMD-QOSM
The bi-directional successful reservation is similar to a
combination of two unidirectional successful reservations that are
accomplished in opposite directions, see Figure 11. 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 11 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 <B> bit of the "PHR RMD control information" field indicates
a bi-directional reservation and is set to "1".
* the "PDR RMD control information" field is included into the
RESERVE(RMD-QSPEC): "forward" message. The value of the PDR
<PDR Control Type> is "1", i.e., "PDR_Reservation_Request".
* the <PDR B> 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 response "PDR RMD control information" field sent by a QNE
egress to a QNE ingress node is not carried by a RESPONSE
message, but it is carried by a RESERVE message that is sent by
the QNE egress node towards the QNE ingress node (denoted in
Figure 11 as RESERVE (RMD-QSPEC): "reverse").
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 value of the <Bandwidth> field 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 <B> bit of the "PHR RMD control information" field
indicates a bi-directional reservation and is set to "1"
* the "PDR RMD control information" field is included into the
RESERVE(RMD-QSPEC): "reverse" message. The value of the PDR
<PDR Control Type> is "4", i.e., "PDR_Reservation_Report"
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* the <PDR B> bit indicates a bi-directional reservation and is
set to "1"
* the value of the <PDR BOUND_SESSION_ID> field 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.
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 11: Intra-domain signaling operation for successful
bi-directional reservation
Figure 12 and Figure 13 show the flow diagrams used in case of a
unsuccessful bi-directional reservation. In the former figure 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 the latter figure 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 12 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 4. 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 37]
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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" | 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 12: Intra-domain signaling operation for unsuccessful
bi-directional reservation (rejection on path QNE(ingress)
towards QNE(egress))
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 13: Intra-domain signaling normal operation for unsuccessful
bi-directional reservation (rejection on path QNE(egress)
towards QNE(ingress))
The main differences between the bi-directional unsuccessful
procedure shown in Figure 13 and the in bi-directional successful
procedure are as follows:
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INTERNET-DRAFT RMD-QOSM
* 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 RMD control information" and "PDR RMD control
information" fields 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 fields. 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 fields it generates a RESERVE(RMD-QSPEC):"reverse - T tear"
message that is sent towards the QNE ingress node.
More details on the operation of the bi-directional reservation
operation will be provided in future versions of this draft.
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 Consideration
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. A certain
degree of trust is, therefore, always assumed in most systems.
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
cannot benefit from security protection. As such, RMD signaling is
target towards intra-domain signaling only. Still it is possible
to provide some degree of security.
In the context of RMD QOSM signaling a classification between
in-path adversaries and off-path adversaries needs to be made.
Furthermore, it might be necessary to differentiate between always
off-path nodes and nodes which are only off-path with regard to a
specific signaling message.
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The following paragraph aims to raise a discussion about the
requirements placed on the security properties of the signaling
message exchange:
First, it is necessary to protect the message communication between
the QNE ingress and the QNE egress. This is possible since these
nodes are meant to be stateful nodes and do not suffer from the same
constraints as network QNE interior nodes. This mechanism already
ensures that intermediate or off-path nodes initiate some signaling
messages towards the edges. An adversary is therefore unable to
inject an NOTIFY message or a RESERVE message. Additionally, such a
security protection ensures that only selected fields can be
modified. To accomplish this type of protection two mechanisms need
to be considered that both require enhancements to the QoS NSLP.
Since the intra-domain RESERVE message travels along several
stateless nodes it is necessary to provide a protection at the
QoS-NSLP. Channel security at the GIMPS layer might in most cases
not be possible due to the nature of the NTLP datagram mode message.
One option is the usage of the Cryptographic Message Syntax (CMS) to
protect selected payloads at the QoS NSLP layer. A digital signature
is suitable if the QNE ingress and the QNE egress node do not need
to share a secret nor do they require an in-band exchange of
certificates due to the closed environment where a pre-distribution
of certificates can be assumed. Such a digital signature would
amount for about roughly 600 to 700 bytes of payloads within a
packet. Further implementation experience will be required to see
whether this message size is within the MTU limits for the entire
NSIS message. The usage of a digital signature for a one-shot packet
would, however, allow an adversary located within the intra-domain
network to flood the QNE ingress or QNE egress with digitally signed
messages. This would require heavy computation by the target nodes
and could lead to a denial of service. The usage of an out-of-band
authentication and key exchange protocol extending the Internet Key
Exchange Protocol using a Domain of Interpretation is a good
alternative. An example of this approach was exercised in [RSVP-DOI].
The QNE ingress node should know its QNE egress node based on either
an end-to-end signaling communication. In the reverse direction
routing state has been established as part of GIMPS signaling.
Furthermore, it is necessary to enforce consistence checks within
the protocol itself. Certain QOS-NSLP objects MUST be defined that
can be used to enforce these checks, see Section 7.3. For example,
it must be ensured that flows belonging to a particular path are
terminated when a congestion indication was received and not flows
that travel a different path through the RMD aware network domain.
This check is necessary to prevent malicious nodes to affect the
entire network. The QNE egress node needs to verify that only fields
that are allowed to be modified that are predefined for this
purpose. This allows abnormal behavior to be detected. For some
scenarios, an additional verification can be provided by matching
the end-to-end signaling communication with the intra-domain
signaling communication, see e.g., Section 3.2.2.
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The congestion handling mechanism is very difficult to detect since
the malicious behavior might be hard to distinguish from regular
behavior. Hence, intrusion detection techniques and statistical
measurements could help to detect a malicious node within the RMD
aware network doamin. This technique has been suggested also for
DiffServ Codepoint packet marking (add ref. later). A general
observation can be made here that a router implementing a QoS
signaling protocol (and the RMD QOSM) can, similar to a router
without support for QoS signaling, do a lot of harm to a system.
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. More details on open issues will be provided in a
future version of this draft.
7.1 Explicit congestion notification
Explicit congestion notification (ECN) described in RFC 3168 might
be used to complement RMD basic functions. Congestion notification
can be based on queue management, e.g. RED.
7.2 Bi-directional severe congestion handling
The future version of this draft will describe the
bi-directional severe congestion handling within the RMD
aware domain when a bi-directional resource reservation
and/or resource query procedure is applied.
7.3 QoS-NSLP objects required for security considerations
The current version of this draft uses the RII and <PDR_NONCE>
parameters for solving security consideration issues. Future
versions of the QoS-NSLP draft [QoS-NSLP] and of this draft
will consider these concerns.
8. Acknowledgments
The authors express their acknowledgement to people who have worked
on the RMD concept: Z. Turanyi, R. Szabo, A. Csaszar, A. Takacs, 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.
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9. Authors' Addresses
Attila Bader
Traffic Lab
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
10. Normative References
[QoS-NSLP] Bosch, S., Karagiannis, G. and A. McDonald, "NSLP for
Quality-of-Service signaling", draft-ietf-nsis-qos-nslp-05 (work
in progress), October 2004.
[QSP-T] Ash, J., Bader, A., Kappler C., "QoS-NSLP QSpec Template"
draft-ietf-nsis-QSpec-02 (work in progress), June 2004.
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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., "GIMPS: General Internet
Messaging Protocol for Signaling", draft-ietf-nsis-ntlp-04
(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.
[RMD3] Marquetant A., Pop O., Szabo R., Dinnyes G., Turanyi Z.,
"Novel Enhancements to Load Control - A Soft-State, Lightweight
Admission Control Protocol", Proceedings of the 2nd International
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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12. Intellectual Property Statement
IPR Statement about RMD
I hereby give the following IPR Disclosure in relation to the RMD
concept proposed by Ericsson and currently under discussion in IEFT
WG NSIS:
To the best of my knowledge there are no Ericsson patents or filed
patent applications on RMD protocol operation or basic principles.
To my knowledge there is only one Ericsson patent application family
that could possibly be relevant merely to particular implementation
of RMD. This patent family comprises US patent 6687655 and
counterparts in other countries.
To the best of my knowledge there is only one Ericsson owned
invention without any patent applications filed yet that could
possibly be relevant to particular implementation of RMD, but this
invention is not relevant to RMD protocol operation or basic
principles.
I have been authorized by Ericsson to give the following Licensing
Declaration in relation to the RMD concept proposed by Ericsson and
discussed in IEFT WG NSIS:
In case a license to a patent in the patent family above or a patent
issued/granted on an application for patent on the invention above
should be necessary for implementing any Internet Standard, Ericsson
is willing to grant to anybody a license to such patent on fair,
reasonable and non-discriminatory conditions for the implementation
of the standard, subject to reciprocity.
Attila Bader
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology
described in this document or the extent to which any license
under such rights might or might not be available; nor does it
represent that it has made any independent effort to identify any
such rights. Information on the procedures with respect to rights
in RFC documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr.
Bader, et al. [Page 44]
INTERNET-DRAFT RMD-QOSM
The IETF invites any interested party to bring to its attention
any copyrights, patents or patent applications, or other
proprietary rights that may cover technology that may be required
to implement this standard. Please address the information to the
IETF at ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
