NSIS Working Group Attila Bader
INTERNET-DRAFT Lars Westberg
Ericsson
Expires: July 2005 Georgios Karagiannis
University of Twente
Cornelia Kappler
Siemens
Tom Phelan
Sonus
February 15, 2005
RMD-QOSM - The Resource Management in Diffserv QoS model
<draft-ietf-nsis-rmd-01.txt>
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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 network. RMD
ingress edge nodes aggregate the requests and signal the aggregated
requests through internal nodes along the data path to the egress
edge nodes. Egress nodes reconstitute the original, disaggregated,
requests and continue forwarding them along the data path towards
the final destination.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . .3
3. Overview of RMD and RMD-QOSM . . . . . . . . . . . . . .. . .4
3.1 RMD . . . . . . . . . . . . . . . . . . . . . . . . . . .4
3.2 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 . . . . . . . . . . . . . . . . . . 9
4.1.1 RMD-QOSM QoS descriptor . . . . . . . . . . . . . .9
4.1.2 PHR RMD-QOSM control information . . . . . . . . . 9
4.1.3 PDR RMD-QOSM control information . . . . . . . . 11
4.1.4 Mapping of QSpec parameters onto generic
QSpec Parameters . . . . . . . . . . . . . . . . .13
4.2 Message format . . . . . . . . . . . . . . . . . . . . .13
4.3 RMD node state management . . . . . . . . . . . . . . . 14
4.4 Operation and sequence of events . . . . . . . . . . . .16
4.4.1 Edge discovery and addressing of messages . . . . 16
4.4.2 Basic unidirectional operation . . . . . . . . . .17
4.4.2.1 Successful reservation. . . . . . . . . . . .17
4.4.2.2 Unsuccessful reservation . . . . . . . . . . 22
4.4.2.3 RMD refresh reservation. . . . . . . . . . . 23
4.4.2.4 RMD modification of reservation. . . . . . . 28
4.4.2.5 RMD release procedure. . . . . . . . . . . . 28
4.4.2.6 Severe congestion handling . . . . . . . . .34
4.4.3 Bidirectional operation . . . . . . . . . . . . . 37
4.4.3.1 Successful and unsuccessful reservation . . .38
4.5 Handling of additional errors . . . . . . . . . . . . . 42
5. Security Consideration. . . . . . . . . . . . . . . . . . . 42
6. IANA Considerations. . . . . . . . . . . . . . . . . . . . .43
7. Open issues. . . . . . . . . . . . . . . . . . . . . . . . .44
7.1 Explicit congestion notification . . . . . . . . . . . .44
7.2 Bidirectional severe congestion handling . . . . . . . .44
8. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . .44
9. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . 44
10. Normative References . . . . . . . . . . . . . . . . . . . 45
11. Informative References . . . . . . . . . . . . . . . . . . 45
12. Intellectual Property Rights . . . . . . . . . . . . . . . 46
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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:
* aggregation of individual resource reservation or resource query
requests at the ingress node of the domain,
* hop-by-hop admission control (of aggregated requests) within the
domain. There are two possible modes of operation for internal
nodes to admit aggregated 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 a 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 uses the stateless/reduced
state operation mode of QoS-NSLP and 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 complex 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 operation modes are described: measurement-based
admission control 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
RMD-QOSM is a QoS-NSLP QoS model for networks that uses RMD. 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 QNF nodes that are the ingress and egress nodes in the
RMD domain (QNF Ingress and QNF Egress), and QNF nodes that are
interior nodes (QNF Interior).
All nodes of the RMD domain are QoS-NSLP aware nodes. Edge nodes
store and maintain QoS-NSLP and NTLP states and therefore are
stateful nodes. The interior nodes are NTLP stateless. Furthermore
they are either QoS-NSLP stateless (for measurement-based
operation), or are reduced state nodes storing per PHB aggregated
QoS-NSLP states (for reservation-based operation). Note that for
both cases, the interior nodes do not store any NTLP states.
|------| |-------| |------| |------|
| 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 QNF QNF QNF QNF 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
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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 4.4.2.6).
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 a generic QSpec describing the
reservation and forwarded along the path towards the QNR. When the
RESERVE message arrives at the ingress node, an RMD-QSpec is
constructed. The RMD-QSpec is sent in a local, independent RESERVE
message through the interior nodes towards the QNR. This 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 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. 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. When the message reaches the egress node,
if no intermediate node has denied the reservation, 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 interior node has denied the reservation, then the reservation
fails and a RESPONSE message is sent directly from the egress node
to the ingress node.
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.
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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.
QNF QNF QNF QNF
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
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.
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4.1. RMD-QSpec Definition
The RMD-QOSMQSpec object contains three fields, the "RMD-QOSM QoS
descriptor", the Per Hop Reservation "PHR RMD-QOSM control
information" and the Per Domain Reservation "PDR RMD-QOSM control
information". The "RMD-QOSM QoS descriptor" 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 by the edge nodes and is not available (carried) by
the "PHR RMD-QOSM control information". Note that it is required
that the consistency between the RMD-QOSM QSpec parameters and the
QSpec Template draft [QSP-T] should be ensured.
4.1.1. RMD-QOSM QoS descriptor
This section describes the parameters used by the "RMD-QOSM QoS
descriptor" field. The RMD-QOSM QoS descriptor only contains the
QoS Desired object [QSP-T]. It does not contain the QoS
Available, QoS Reserved or Minimum QoS objects.
<RMD-QOSM QoS descriptor> = <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. The <NSLP hops> and<Max NSLP Hops>
parameters are defined in <QSM-T>. All other parameters are
specific to RMD-QOSM.
<PHR RMD-QOSM control information> = <PHR Type> <Control Type>
<S> <Overload %> <M> <NSLP Hops> <Hop_U> <B> <Time Lag>
<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.
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"PHR_Resource_Request" (Control Type = 1): initiate or update
the traffic class reservation state on all nodes located on
the communication path between the QNF(ingress) and
QNF(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 QNF(ingress) and QNF(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 QNFs 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 QNF, this QNF sets the M bit in order to
notify the egress QNF.
<NSLP Hops>:
8 bit field. The <NSLP Hops> in RMD domain counts the number of
hops where the reservation was successful. The <NSLP Hops>is set
to zero when a RESERVE message enters a domain and increased by one
at each interior QNF. However when a QNF is reached that does not
have sufficient resources to admit the reservation, the M Bit is
set, and the <NSLP Hops> value is frozen.
<Hop_U> (NSLP_Hops unset):
1-bit. The QNF(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 <NSLP Hops> value. This is the case when an
RMD-QOSM reservation-based node is not admitting the "RMD-QOSM
QoS descriptors" and "PHR_Resource_Request" control information
fields. When <Hop_U> is set ô1ö the <NSLP Hops> SHOULD NOT be
changed.
<B>: 1 bit. Indicates bi-directional reservation.
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<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 used by 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
QNF(ingress) node in order to initiate or update the QoS-NSLP
per domain reservation state in the QNF(egress) node
"PDR_Refresh_Request" (Control Type = 2): generated by the
QNF(ingress) node and sent to the QNF(egress) node to refresh,
in case needed, the QoS-NSLP per domain reservation states
located in the QNF(egress) node
"PDR_Release_Request" (Control Type = 3): generated and sent
by the QNF(ingress) node to the QNF(egress) node to release
the per domain reservation states explicitly
"PDR_Reservation_Report" (Control Type = 4): generated and
sent by the QNF(egress) node to the QNF(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 QNF(egress) node in case needed, to the QNF(ingress) node
to report that a "PHR_Refresh_Update" control information
field has been received and has been processed
"PDR_Release_Report" (Control Type = 6) generated and sent by
the QNF(egress) node in case needed, to the QNF(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_Request_Info" (Control Type =7): an object that can be
used as a common "PDR_Reservation_Request",
"PDR_Refresh_Request", "PDR_Release_Request" and
"PDR_Modification_Request"
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"PDR_Congestion_Report" (Control Type = 8): generated and sent
by the
QNF(egress) node to the QNF(ingress) node and used for Severe
congestion notification
"PDR_Modification_Request" (Control Type = 9): generated and
sent by the QNF(ingress) node to the QNF(egress) node to
modify the per domain reservation states located in the
QNF(egress) node
"PDR_Modification_Report" (Control Type =10): generated and
sent by the QNF(egress) node to QNF(ingress) node to report
that the combination of either the "PHR_Resource_Request" and
the "PDR_Modification_Request" control information fields or
the "PHR_Release_Request" and the "PDR_Modification_Request"
control information fields have been received and processed
<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" control
information fields. This parameter applies only to
"PDR_Reservation_Report", "PDR_Refresh_Report",
"PDR_Congestion_Report" and "PDR_Modification_Report" control
information fields.
<PDR_Overload %>:
8-bit. Indicates the level of overload to the ingress
node. It includes the Overload % of the
"PHR_Resource_Request" or "PHR_Refresh_Update" control
information fields. This parameter applies only to
"PDR_Reservation_Report", "PDR_Refresh_Report",
"PDR_Congestion_Report" and "PDR_Modification_Report" control
information fields.
<PDR M> (Marked):
1-bit. Carries the <M> value of the "PHR_Resource_Request" or
"PHR_Refresh_Update" control information fields. This
parameter applies only to "PDR_Reservation_Report",
"PDR_Refresh_Report", "PDR_Congestion_Report" and
"PDR_Modification_Report" control information fields.
<PDR B>: 1 bit Indicates bi-directional reservation.
<Max NSLP Hops>:
8-bit. The <Max NSLP 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" control information field
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<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.
<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.
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]
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The format of a Query message used by the
RMD-QOSM is as follows:
QUERY = COMMON_HEADER
[ RII ][ BOUND_SESSION_ID ]
[ POLICY_DATA ] [ RMD-QSPEC ]
A QUERY message MUST contain an RII object to indicate a RESPONSE is
desired, unless the QUERY is being used to initiate reverse-path
state for a receiver-initiated reservation.
The format of a local (intra-domain) RESPONSE message used by
the RMD-QOSM is as follows:
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.
QNF 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.
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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 be forwarded unchanged.
QNF 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. For reservation-
based nodes, per PHB group aggregated reservations states are
installed and are maintained by sending intra-domain RESERVE
messages.
The reservation-based PHR installs and maintains one reservation
state per PHB, in all the nodes located in the
communication path from the QNF ingress node up to the QNF egress
node. This state represents the number of currently reserved
resource units that are carried by the PHR object for the admitted
incoming flows. Thus, the QNF ingress node signals only the
resource units requested by each flow. These resource units if
admitted are added to the currently reserved resources per PHB.
For each PHB a threshold is maintained that specifies the maximum
number of resource units that can be reserved. This threshold
could, for example, be statically configured.
The per-PHB group reservation states are soft states but explicit
release can also be used. When the reservation soft state principle
is used, a finite lifetime is set for the length of the reservation.
These reservation states are refreshed by sending periodic refresh
messages. 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. The refresh period
can be refined using a sliding window algorithm described in [RMD1].
The QNF edges maintain either per flow, or aggregated QoS-NSLP
reservation states. Each per flow or aggregated QoS-NSLP
reservation state is identified by a NTLP SESSION_ID (see [GIMPS]).
In RMD, these states are denoted as PDR states.
In the situation where the QNF 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.
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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 the
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 4.4.2.4).
4.4. Operation and sequence of events
This section describes the operation and the sequence of events in
the RMD-QOSM.
The transport characteristics for the intra-domain (local)
reservation model can be different from that of the inter domain
(end-to-end) reservation model. GIMPS can be used in a different
way for the edge-to-edge and hop-by-hop sessions, (i.e. sending of
messages in datagram mode, and not retaining optional path state,
i.e., NTLP stateless mode). The reduced state reservation can be
updated independently of the per-flow inter domain (end-to-end)
reservations.
4.4.1. 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 messages addressed to the end node are
intercepted and terminated by the egress node.
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4.4.2. 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.
4.4.2.1. 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 QNFs at the edges of the RMD domain support the
local and end-to-end QoS models, which process the RESERVE message
differently.
4.4.2.1.1. Operation in ingress node
When an end-to-end reservation request (RESERVE) arrives at the
ingress node (QNF), after classifying it into the appropriate PHB,
the ingress node calculates the requested resource unit and creates
a QoS reservation at the QNF ingress node itself. This state is
associated with the SESSION ID. If the request was satisfied
locally, the ingress node generates two RESERVE messages:
end-to-end and intra-domain RESERVE messages. These are bounded
together including a BOUND_SESSION_ID in the intra-domain RESERVE
message. The end-to-end RESERVE message is sent to the egress QNF
and includes the end-to-end QSpec. This message is forwarded using
facilities provided by the NTLP to bypass the stateless or reduced-
state nodes, see Figure 3. After completing the initial discovery
phase, the GIMPS connection mode between the QNF ingress and QNF
egress can be used. The QNF ingress node instructs the NTLP to
bypass all intermediate nodes towards the egress node for the
end-to-end RESERVE message. In this way all the QNF interior nodes
ignore the processing of the end-to-end RESERVE message. At the
egress node the end-to-end RESERVE message is then forwarded as
defined in [QoS-NSLP].
For the intra-domain RESERVE message the QoS descriptor used by the
QSpec of the end-to-end QoS model needs to be transformed into the
<Bandwidth> and <PHB-CLASS> RMD QoS descriptor. In order to
make a RMD query or a RMD reservation an intra-domain
RESERVE(RMD-QSPEC) message is generated by the QNF ingress.
Before generating this message, the RMD-QOSM functionality uses the
<Bandwidth> RMD QoS descriptor for admission control:
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* When the RMD reservation-based method is used, the resources
specified in <Bandwidth>, are added to the currently
reserved resources per traffic class (PHB) and
they become a part of the per RMD traffic class (PHB)
reservation state. Furthermore, the value of the <NSLP Hops>
field has to be set
to one.
* When the RMD measurement-based method is used, and admission
decision is positive, the MBAC algorithm is updated with these
resources.
The session ID used by the intra-domain RESERVE (RMD-QSPEC) message
MUST be associated to a PHB value (<PHB-CLASS>). The IP destination
address of this message MUST be the same as the IP destination
address of the end-to-end RESERVE message. The QNF ingress node
generates a reservation request "PHR RMD control information" field
denoted as "PHR_Resource_Request" and it MAY generate a reservation
request "PDR RMD control information" field denoted as
"PDR_Reservation_Request". These two fields together with the "RMD
QoS descriptors" field form the RMD-QSPEC object. This intra-domain
RESERVE (RMD-QSPEC) message MUST include a "PHR RMD control
information" (PHR_Resource_Request) field, and it MAY include the
"PDR RMD control information", (PDR_Reservation_Request) field.
The intra-domain RESERVE message MUST be used and/or set by the QNF
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 QNF edges MUST
be configured as boundary nodes and the QNF 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 QNF ingress node.
* the PHR resource units MUST be included into the <Bandwidth>
parameter of the "RMD QoS descriptor" 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 <NSLP Hops> parameter in the "PHR RMD control
information" MUST be set to "1".
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* 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"
* the "PDR RMD control information" field MUST be included into the
RESERVE(RMD-QSPEC): "forward" message. The value of the PDR
<PDR Control Type> is "1", i.e., "PDR_Reservation_Request".
* the value of the <PDR NONCE> MUST contain the Response
Identification Information value of the ingress QNF, 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.
4.4.2.1.2 Operation in the Interior nodes
The RMD query procedure is used in the case of the RMD measurement
based method, while the RMD reservation procedure
is used in case of reservation-based method, see e.g., [RMD1].
Each QNF interior node MUST use and/or set the QoS-NSLP and
RMD-QOSM parameters of the intra-domain RESERVE (RMD-QSPEC)
message as follows:
* the values of the <RSN>, <RII>, <REFRESH_PERIOD>,
<BOUND_SESSION_ID>, <POLICY_DATA> objects are not changed,
i.e., equal to the values set by the QNF ingress. These values
are not used by the QNF interior;
* the flag "Acknowledge" (A) SHOULD be set "OFF"
* the value of <Bandwidth> parameter of the "RMD QoS
descriptors" field is used by the QNF 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 <NSLP 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.
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4.4.2.1.3 Operation in the egress node
When the intra-domain RESERVE (RMD-QSPEC) is received by the QNF
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 "PHR RMD control information" field (and if available the "PDR
RMD control information") are read and processed by the RMD QoS
signaling model functionality. The value of <Bandwidth> (and
<PHB-CLASS>) of the "RMD QoS descriptors" field is used by the
QNF egress node for traffic class admission control.
* In case of the RMD reservation-based procedure, these
resources, if are admitted, are added to the currently
reserved resources per PHB and therefore they will become a
part of the per PHB reservation state. Furthermore, the value
of the <NSLP Hops> parameter in the "PHR RMD control
information" field has to be increased by one.
* In case of the RMD measurement-based method, the MBAC
algorithm is updated by the number of these resources, if the
admission control decision is positive.
QNF (ingress) QNF (interior) QNF (interior) QNF (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
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The end-to-end RESERVE message is only forwarded further 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.
In return, after a positive response (i.e., successfully processed
end-to-end RESPONSE message) the end-to-end RESPONSE message that
has been initiated by the QNR arrives at the QNF egress. The QNF
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.
The non-default values of the objects contained in the end-to-end
RESPONSE message MUST be used and/or set by the QNF 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.
* 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.
This end-to-end RESPONSE (PDR) message is received by the QNF
ingress node. The non-default values of the objects contained in
the end-to-end RESPONSE message that is forwarded out the RMD
domain, MUST be used and/or set by the QNF ingress node as follows:
* the values of the <RII/RSN>, <ERROR_SPEC>, [ *QSPEC ] objects
are set by the standard QoS-NSLP protocol functions;
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* the "PDR RMD control information" field has to be processed
and removed by the RMD-QOSM functionality in
the QNF 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 QNF ingress nodes SHOULD also de-activate the
"NTLP QoS-NSLP-E2E-IGNORE" feature. 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.
4.4.2.2. Unsuccessful reservation
This section describes the operation where a request for reservation
cannot be satisfied by the RMD-QOSM.
The QNF ingress, the QNF interior and QNF 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
4.4.2.1. The main difference between the unsuccessful operation and
successful operation is that one of the QNF nodes does not admit the
request due to lack of resources. This also means that the QNF edge
node MUST NOT forward the end-to-end RESERVE message towards the
QNR node and it MUST be discarded.
When an end-to-end RESERVE message arrives to the QNF ingress and
if there are no resources available locally, the QNF 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 (i.e., intra-domain
RESERVE(RMD-QSPEC)is not admitted by the QNF interior node then
the <Hop_U> and <M> parameters of the "PHR RMD control information"
MUST be set to "1". The <NSLP 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 QNF node, then the <M> parameter of the "PHR RMD control
information" field MUST be set to "1".
In general, if a QNF 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 descriptors" fields MUST NOT be processed, i.e., their
parameters will neither be read nor modified.
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In the RMD reservation based and RMD measurement
based scenario, when the <M> marked intra-domain RESERVE (RMD-QSPEC)
is received by the QNF 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 QNF 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). Note that this message will use a
NTLP/GIMPS connection mode. The QNF egress requests from NTLP/GIMPS
to activate the QoS-NSLP-E2E-IGNORE feature. The non-default values
of the objects contained in the end-to-end RESPONSE (PDR) message
MUST be used and/or set by the QNF 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 <NSLP 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_NSLP 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.
* 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 QNF ingress
node, which receives this message, as follows:
* the values of the <RII/RSN>, <ERROR_SPEC> ], [*QSPEC] objects
are set by standard QoS-NSLP protocol functions;
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* the PDR object has to be processed and removed by the RMD QoS
signaling model functionality in the QNF 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
4.4.2.5). The QNF ingress nodes SHOULD also de-activate the
"NTLP QoS-NSLP-E2E-IGNORE" feature.
QNF (ingress) QNF (interior) QNF (interior) QNF (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, <NSLP Hops>=<Max_NSLP Hops>) |
|------------------->| | |
Figure 4: Basic operation during unsuccessful reservation
initiation used by the RMD-QOSM
4.4.2.3 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 QNF 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 QNF edges, depends on the locally maintained
refreshed interval (see [QoS-NSLP]). The QoS-NSLP-E2E-IGNORE
feature of NTLP/GIMPS MUST be activated by QNF ingress and
deactivated by the QNF egress node.
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The ingress node MUST be able to generate a 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 QNF edge and QNF interior nodes and SHOULD be smaller (default:
more than two times) than the refresh period at the QNF ingress node
used by the end-to-end RESERVE message. This intra-domain RESERVE
(RMD-QSPEC) message MUST include a "RMD QoS descriptors" field and a
"PHR control information" field (i.e., PHR_Refresh_Update), and it
MAY include a "PDR RMD control information" field, (i.e.,
PDR_Refresh_Request).
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 QNF ingress node. Note
that this aggregation procedure is different than the RMD traffic
class aggregation procedure. One example approach 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., QNF ingress) and the IP destination address of this
message is the IP address of the De-aggregator (i.e., QNF egress).
Another example approach is the approach used in "RSVP Refresh
Overhead Reduction Extensions" ([RFC2961]). If no aggregation
procedure is possible then the IP destination address of this
message should 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.
QNF (ingress) QNF (interior) QNF (interior) QNF (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 QNF ingress in the same
way as described in Section 4.4.2.1. The following objects are
used and/or set differently:
Bader, et al. [Page 25]
INTERNET-DRAFT RMD-QOSM
* the flag "Acknowledge" (A) SHOULD be set "OFF"
* 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 QNF ingress node (e.g., the sum of all the PHR requested
resources of the aggregated flows). If no flow aggregation is
accomplished by the QNF 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 QNF, that is
unique within a session and different for each message (see
[QoS-NSLP]). In general downstream nodes that desire
The intra-domain RESERVE (RMD-QSPEC) message is received and
processed by the QNF interior nodes. Any QNF edge or QNF 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 QNF interior node in the same way as described in Section 4.4.2.1.
The following objects are used and/or set differently:
* the value of <Bandwidth> parameter of the "RMD QoS descriptors"
field is used by the QNF 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 descriptors" field (i.e., <Bandwidth>),
whether it is marked or not, is always processed, but marked bits
are not changed.
Bader, et al. [Page 26]
INTERNET-DRAFT RMD-QOSM
The intra-domain RESERVE (RMD-QSPEC) message is received and
processed by the QNF egress node. The "RMD QoS descriptors" and the
"PHR RMD control information" fields (and if available the "PDR RMD
control information") are read and processed by the RMD QoS
signaling model functionality. The value of <Bandwidth> parameter
of the "RMD QoS descriptors" is used by the QNF egress node for
refreshing the RMD traffic class state. If the refresh procedure
cannot be fulfilled then the <M> parameter of the "PHR RMD control
information" field has to be set to "1".
A new intra-domain RESPONSE (PDR) message is generated by the
QNF egress node. This message MUST include a "PDR RMD control
information" (of type PDR_Refresh_Report).
This intra-domain RESPONSE (PDR) message MUST be sent to the QNF
ingress node, i.e., previous stateful hop. This can, for example,
be accomplished by using the value of the <RII> included in the
received intra-domain RESERVE(RMD- QSPEC) message. In general
downstream nodes that desire responses MAY keep track of this RII to
identify the RESPONSE when it passes back through them. This <RII>
value MUST be included in the <RII> object of the generated
intra-domain RESPONSE (PDR) message. The most of the non-default
values of the objects contained in this refresh intra-domain
RESPONSE (PDR) message MUST be set by a QNF egress node in the same
way as described in Section 4.4.2.1.
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 QNF 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 to "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 QNF ingress node, then:
* the values of the <RII/RSN>, <ERROR_SPEC>, [ *QSPEC] objects
are processed by the standard QoS-NSLP protocol functions;
Bader, et al. [Page 27]
INTERNET-DRAFT RMD-QOSM
* the "PDR RMD control information" has to be processed and
removed by the RMD-QOSM functionality in the
QNF 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 QNF ingress node has to
generate (in a standard QoS-NSLP way) an error end-to-end
RESPONSE message that will be sent towards QNI.
4.4.2.4. RMD modification of reservation
When the RMD QoS model functionality of the QNF ingress node
receives an end-to-end RESERVE message that is requesting a
modification on the number of reserved resources then the following
procedure is applied. When the modification request requires an
increase on the number of reserved resources, then the RMD QoS
model functionality of the ingress node MUST add the old and
already reserved number of resources from the number of resources
included in the new modification request. The result of this
subtraction MUST be introduced within the <Bandwidth> parameter of
the "RMD QoS descriptors" field, which is sent together with a
"PHR_Resource_Request" control information field. If a QNF edge or
QNF 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 a unsuccessful
reservation functionality will be applied (see Section 4.4.2.2).
When the modification request requires a decrease on the number of
reserved resources, then the QNF ingress node will have to subtract
the number of resources included in the new modification request
from the old and already reserved number of resources. The result
of this subtraction MUST be introduced in the <Bandwidth>
parameter of the "RMD QoS descriptors" field, which is sent together
with a PHR_Release_Request control information field. Subsequently
a RMD release procedure SHOULD be accomplished (see Section 4.4.2.5).
4.4.2.5 RMD release procedure
If a refresh RESERVE message does not arrive at a QNF 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.
Bader, et al. [Page 28]
INTERNET-DRAFT RMD-QOSM
When the RMD-RMF of a QNF edge or QNF interior node processes a
"PHR_Release_Request" control information field it MUST identify the
value of the <PHB-CLASS> parameter included in the "RMD QoS
descriptors" field, and estimate the refresh period where it last
signaled the resource usage (where it last processed a
"PHR_Refresh_Update" control information field). This MAY be done
by, for example, giving the opportunity to a QNF ingress node to
calculate the time lag, say "T_lag", between the last sent
"PHR_Refresh_Update" control information field and the
"PHR_Release_Request" control information field. The value of this
time lag "T_Lag", is first normalized to the length of the refresh
period, say "T_period". In other words, the ratio between this time
lag, "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 (QNF edge or QNF interior) receives this
"PHR_Release_Request" control information, it MUST store its arrival
time. Then it MUST calculate the time difference, say "Tdiff",
between this 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.
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 descriptors" 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 4.4.2.5.1) 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 (see Section
4.2.2.2) or "PDR_Congestion_Report" control information field (see
Section 4.4.2.6).
4.4.2.5.1. 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 QNF ingress
then the QNF 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
Bader, et al. [Page 29]
INTERNET-DRAFT RMD-QOSM
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.
This intra-domain RESERVE (RMD-QSPEC) message MUST include a "RMD
QoS descriptors" 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.
QNF (ingress) QNF (interior) QNF (interior) QNF (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
The most of the non default values of the objects contained in the
tear intra-domain RESERVE message are set by the QNF ingress node in
the same way as described in Section 4.4.2.1. 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 QNF ingress node does not need to receive a
response from the QNF egress node;
* the TEAR flag is set to ON;
* the PHR resource units MUST be included into the <Bandwidth>
parameter of the "RMD QoS descriptors" field;
* the value of the <NSLP Hops> parameter has to be set to one.
Bader, et al. [Page 30]
INTERNET-DRAFT RMD-QOSM
* 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 4.4.2.5)
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 QNF 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 QNF interior node in the same way
as described in Section 4.4.2.1. The following objects are set and
processed differently:
* Any QNF interior node that receives the combination of the "RMD
QoS descriptors" 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 4.4.2.5
The intra-domain tear RESERVE (RMD-QSPEC) message is received and
processed by the QNF egress node. The "RMD QoS descriptors" 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 descriptors" 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.,
QNF egress) only if the intra-domain tear RESERVE (RMD-QSPEC)
message arrives at the QNF egress node. The QoS-NSLP-E2E-IGNORE
feature of NTLP/GIMPS MUST be deactivated.
4.4.2.5.2 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 4.4.2.2) or an intra-domain
NOTIFY (PDR) message (see Section 4.4.2.6) with a <M> or <S> marked
"PDR RMD control information" field. This RMD specific release
procedure can be terminated at any QNF edge or any QNF interior
node. This is determined using the <Max_NSLP Hops> field. node.
Bader, et al. [Page 31]
INTERNET-DRAFT RMD-QOSM
The RMD specific explicit release procedure that is
terminated at a QNF interior (or QNF 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 4.4.2.2) or severe congestion
(see Section 4.4.2.6). When the RMD QoS signaling model
functionality of a QNF 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 QNF 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 descriptors> 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.
QNF (ingress) QNF (interior) QNF (interior) QNF (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 descriptors> field and a "PDR RMD control
information field",
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.
Bader, et al. [Page 32]
INTERNET-DRAFT RMD-QOSM
The most of the non-default values of the objects contained in the
tear intra-domain RESERVE (RMD-QSPEC) message are set by the QNF
ingress node in the same way as described in Section 4.4.2.1.
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 NSLP 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 NSLP 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.
QNF (ingress) QNF (interior) QNF (interior) QNF (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, <NSLP Hops>=<Max_NSLP Hops>)|
|------------------->| | |
| | | |
Figure 8: Basic operation during RMD explicit release procedure
Triggered by RESPONSE used by the RMD-QOSM
Any QNF edge or QNF interior node that receives a combination of the
"RMD QoS descriptors" 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
Bader, et al. [Page 33]
INTERNET-DRAFT RMD-QOSM
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 4.4.2.5. Furthermore, the <NSLP 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_NSLP Hops> value included in the "PDR RMD
control information" field MUST be compared with the calculated
<NSLP 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 QNF node
that is currently processing this message was the last QNF node that
successfully processed the "RMD QoS descriptors" and "PHR RMD
control information" fields of its associated initial reservation
request (i.e., initial intra-domain RESERVE (RMD-QSPEC) message).
Its next QNF downstream node was unable to successfully process the
initial reservation request, and therefore this QNF 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 QNF interior
node, but it will be forwarded in the downstream direction. The QNF
egress node will receive and process the PHR_Resource_Release
control information field. Afterwards, the QNF egress node MUST
terminate the intra-domain RESERVE (RMD-QSPEC) object.
4.4.2.6. 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.
The QoS-NSLP and RMD are able to cope with congested situations
using the refresh procedure, see Section 4.4.2.3. If the refresh is
not successful in an QNF 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. 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 have be used, which are described below.
Bader, et al. [Page 34]
INTERNET-DRAFT RMD-QOSM
4.4.2.6.1 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. ECN congestion
notification will be discussed in IETF62 and may be considered in
the next version of the draft.
4.4.2.6.2 Severe congestion using proportional data packet marking
Typically, routing algorithms are able to adapt and change their
routing decisions to reflect changes in the topology (e.g., link
failures) and traffic volume. In such situations, the re-routed
traffic follows a new path. Nodes located on this new path MAY
become overloaded after rerouting. Moreover, when a link fails,
the traffic passing through might be dropped, degrading its
performance.
When a 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. 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 QNF Interior node detecting severe congestion marks data packets
passing of the node in which the severe congestion was detected.
For severe congestion marking of the data packet, two code-points
SHOULD be allocated for each traffic class. One is used to indicate
that the packet is passed a congested node. The other code-point
can be used to indicate the degree of congestion. This can be done
for example using the proportional marking method, which means that
the marked bytes are proportional to the degree of congestion. The
QNF 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. For these flows (sessions), the
QNF egress node generates and sends a NOTIFY(PDR) message to the
QNF 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 QNF egress node as follows:
Bader, et al. [Page 35]
INTERNET-DRAFT RMD-QOSM
* 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 "8" (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 QNF 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 shifted to an alternative RMD traffic class
(PHB). An example of such an operation is depicted in Figure 9.
QNF (ingress) QNF (interior) QNF (interior) QNF (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
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
Bader, et al. [Page 36]
INTERNET-DRAFT RMD-QOSM
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.
4.4.3. 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 QNF edge
nodes are common for both upstream and downstream directions,
therefore, the two reservations/sessions can be bound at the QNF
edge nodes.
This bi-directional sender&sender procedure can then be applied
between the QNF edges (QNF ingress and QNF egress) nodes of the RMD
QoS signaling model. In the situation that a security association
exists between the QNF ingress and QNF egress nodes (see Figure 10),
and the QNF ingress node has the required <Bandwidth> parameters
for both directions, i.e., QNF ingress towards QNF egress and QNF
egress towards QNF ingress, then the QNF ingress MAY include both
<Bandwidth> parameters (needed for both directions) into the
RMD-QSPEC within a RESERVE message. In this way the QNF egress node
is able to use the QoS parameters needed for the "egress towards
ingress" direction (QoS-2). The QNF 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 QNF ingress and QNF egress.
|------ RESERVE (QoS-1, QoS-2)----|
| V
| Interior/stateless QNEs
+---+ +---+
|------->|QNE|-----|QNE|------
| +---+ +---+ |
| V
+---+ +---+
|QNE| |QNE|
+---+ +---+
^ |
| | +---+ +---+ V
| |-------|QNE|-----|QNE|-----|
| +---+ +---+
Ingress/ Egress/
statefull QNE statefull QNE
|
<--------- RESERVE (QoS-2) -------|
Figure 10: The bi-directional reservation scenario in the RMD domain
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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 QNF ingress and QNF egress nodes the Bi-directional reservation
for the sender&sender scenario in the RMD domain SHOULD use the
scenario specified in [QoS-NSLP] as ôBi-directional reservation for
sender&sender scenarioö.
Note that in the following sections it is considered that the QNF
edge nodes are common for both upstream and downstream directions
and therefore, the two reservations/sessions can be bounded at the
QNF edge nodes. Furthermore, it is considered that a security
association exists between the QNF ingress and QNF egress nodes,
and the QNF ingress node has the required <Bandwidth> parameters
for both directions, i.e., QNF ingress towards QNF egress and
QNF egress towards QNF ingress.
4.4.3.1 Successful and unsuccessful reservations
This section describes the operation of the RMD-QOSM where a RMD
bi-directional reservation operation is either successfully or
unsuccessfully accomplished.
The bi-directional successful reservation is similar to a
combination of two unidirectional successful reservations that are
accomplished in opposite directions, see Figure 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 QNF ingress node towards the QNF
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".
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INTERNET-DRAFT RMD-QOSM
* the <PDR Reverse Requested Resources> field specifies the
requested bandwidth that has to be used by the QNF egress node to
initiate another intra-domain RESERVE message in the reverse
direction.
* the response "PDR RMD control information" field sent by a QNF
egress to a QNF ingress node is not carried by a RESPONSE
message, but it is carried by a RESERVE message that is sent by
the QNF egress node towards the QNF ingress node (denoted in
Figure 11 as RESERVE (RMD-QSPEC): "reverse").
QNF (ingress) QNF (int.) QNF (int.) QNF (int.) QNF (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
The RESERVE (RMD-QSPEC): "reverse" message is initiated by the QNF
egress node at the moment that the RESERVE (RMD-QSPEC): "forward"
message is successfully processed by the QNF 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"
* the <PDR B> bit indicates a bi-directional reservation and is
set to "1"
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INTERNET-DRAFT RMD-QOSM
* 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.
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 QNF that is not able to support the
requested <Bandwidth> is located in the direction QNF ingress
towards QNF egress. In the latter figure it is considered that the
QNF that is not able to support the requested <Bandwidth> is
located in the direction QNF egress towards QNF ingress.
The main differences between the bi-directional unsuccessful
procedure shown in Figure 12 and the bi-directional successful
procedure are as follows:
* the QNF node that is not able to reserve resources for a
certain request is located in the "forward" path, i.e., path
from QNF ingress towards the QNF egress.
* the QNF 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 QNF egress generates an intra-domain (local)
RESPONSE(PDR) message that is sent towards QNF ingress node.
QNF(ingress) QNF (int.) QNF (int.) QNF (int.) QNF (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 QNF(ingress)
towards QNF(egress))
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INTERNET-DRAFT RMD-QOSM
The main differences between the bi-directional unsuccessful
procedure shown in Figure 13 and the in bi-directional successful
procedure are as follows:
* the QNF node that is not able to reserve resources for a
certain request is located in the "reverse" path, i.e., path
from QNF egress towards the QNF ingress.
* the QNF 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 QNF 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 towards QNF egress
node. The QNF egress node by using the information contained
in the "PHR_Release_Request" and the "PDR_Release_Request"
control information fields it generates a RESERVE(RMD-QSPEC):
"reverse - T tear" message that is sent towards the QNF
ingress node.
QNF (ingress) QNF (int.) QNF (int.) QNF (int.) QNF (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 QNF(egress)
towards QNF(ingress))
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INTERNET-DRAFT RMD-QOSM
More details on the operation of the bi-directional reservation
operation will be provided in future versions of this draft.
4.5 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
The RMD QSP 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.
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.
In the context of RMD QSP 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.
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 QNF ingress and the QNF egress. This is possible since these
nodes are meant to be stateful nodes and do not suffer from the same
constraints as network QNF 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 QNF ingress and the QNF egress node do not need
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INTERNET-DRAFT RMD-QOSM
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 QNF ingress or QNF 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 QNF ingress node should know its QNF egress node based on either
an end-to-end signaling communication. In the reverse direction
routing state has already been established as part of GIMPS
signaling.
Furthermore, it is necessary to enforce consistence checks within
the protocol itself. There are certain parameters in the QOS-NSLP
messages, such as RII and the <PDR NONCE> parameter that can be used
to enforce these checks. 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 QNF
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.
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. A
router can delay, drop, inject, duplicate or modify packets. A
certain degree of trust is, therefore, always assumed in most
systems when they are supposed to participate in the protocol
interaction.
6. IANA Considerations
RMD-QOSM requires a new IANA registry.
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INTERNET-DRAFT RMD-QOSM
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. ECN congestion
notification will be discussed in IETF62 and may be considered in
the next version of the draft.
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.
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, O. Pop, V. Rexhepi, D. Partain, M. Jacobsson, S.
Oosthoek, P. Wallentin, P. Goering, A. Stienstra, M. de Kogel.
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
Bader, et al. [Page 44]
INTERNET-DRAFT RMD-QOSM
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.
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
Bader, et al. [Page 45]
INTERNET-DRAFT RMD-QOSM
[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
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:
Bader, et al. [Page 46]
INTERNET-DRAFT RMD-QOSM
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.
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.
Copyright Statement
Copyright (C) The Internet Society (2004). 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.
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
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