One document matched: draft-jacquenet-cops-te-00.txt
Network Working Group C. Jacquenet
Internet Draft France Telecom
Document: draft-jacquenet-cops-te-00.txt February 2004
Category: Experimental
Expires August 2004
A COPS Client-Type for Traffic Engineering
<draft-jacquenet-cops-te-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 [1].
Internet-Drafts are working documents of the Internet Engineering
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Abstract
This draft specifies a COPS (Common Open Policy Service) client-type
designed for the enforcement of IP Routing and Traffic Engineering
(TE) policies. The usage of this TE COPS client-type relies upon the
activation of the COPS protocol for policy provisioning purposes.
Table of Contents
1. Introduction...............................................2
2. Conventions used in this Document..........................3
3. Terminology Considerations.................................3
4. The Generic Model of an IP Routing/TE Policy
Enforcement Scheme.......................................4
5. TE Client-Type Specific Information to be Carried in
COPS Messages............................................6
5.1. Client-Type Field of the Common Header of Every COPS
Message..................................................7
5.2. COPS Message Content.......................................7
5.2.1. Request Messages (REQ).....................................7
5.2.2. Decision Messages (DEC)....................................8
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5.2.3. Report Messages (RPT)......................................8
5.3. Backward Compatibility Issues..............................9
6. COPS-PR Usage of the TE Client-Type.......................10
7. IANA Considerations.......................................11
8. Security Considerations...................................11
9. References................................................11
10. Acknowledgments...........................................12
11. Author's Address..........................................12
12. Full Copyright Statement..................................13
1. Introduction
The deployment of value-added IP services over the Internet has
become one of the most competing challenges for service providers, as
well as a complex technical issue, from a (dynamic) resource
provisioning perspective.
To address such technical issue, the COPS protocol ([2]) and its
usage for the support of Policy Provisioning ([3]) is one of the
specification efforts of the Resource Allocation Protocol (rap)
Working Group of the IETF that should help service providers by
introducing a high level of automation for the dynamic production of
a wide range of services and policies.
Such policies include routing and traffic engineering policies. They
aim at appropriately provisioning, allocating/de-allocating, and
using the switching and the transmission resources of an IP network
(i.e. the routers and the links that connect these routers,
respectively), according to a set of constraints like Quality of
Service (QoS) requirements (e.g. rate, one-way delay, inter-packet
delay variation, etc.) that have been possibly negotiated between the
customers and the service providers, as well as routing metrics,
which can reflect the network conditions.
Within the scope of this document, the actual enforcement of IP
routing and traffic engineering policies is primarily based upon the
activation of both intra- and inter-domain routing protocols (e.g.
[4], [5], not to mention the use of multicast routing protocols [6])
that will be activated in the network to appropriately select,
install, maintain and possibly withdraw routes that will comply with
the aforementioned QoS requirements and/or specific routing
constraints, depending on the type of traffic that will be conveyed
along these routes.
It is therefore necessary to provide the route selection processes
with the information that will depict the routing policies that are
to be enforced within a domain, including the aforementioned
constraints and metrics, given the dynamic routing protocols actually
support traffic engineering capabilities for the calculation and the
selection of such routes.
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These capabilities are currently being specified in [7] and [8] for
the OSPF (Open Shortest Path First) and the IS-IS (Intermediate
System to Intermediate System routing protocol, [9]) interior routing
protocols respectively, while there is an equivalent specification
effort for the BGP4 (Border Gateway Protocol, version 4) protocol, as
described in [10], for example.
To provide the routers that will participate in the dynamic
enforcement of an IP routing and/or traffic engineering policy with
the appropriate configuration information (such as metrics' values),
one possibility is to use the COPS protocol and its usage for policy
provisioning. To do so, a new COPS client-type is specified, called
the "Traffic Engineering" client-type, and this specification effort
is the purpose of this draft.
This document is organized into the following sections:
- Section 3 introduces terminology as well as basic assumptions,
- Section 4 introduces the generic architecture,
- Section 5 defines the contents of the COPS messages that MUST
include the TE client-type specific information,
- Section 6 defines the usage of the TE client-type, including its
mode of operation with the PDP (Policy Decision Point, [11]) with
whom a COPS communication has been established,
- Finally, sections 7 and 8 introduce IANA and some security
considerations, respectively.
2. Conventions used in this Document
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 [12].
3. Terminology Considerations
The enforcement of an IP routing/TE policy is based upon the
processing of configuration information that reflects the
characteristics of these policies (IGP metric values, BGP attributes'
values, QoS requirements and/or constraints, etc.).
This information is called the "QoS-related" information within the
context of this draft.
Then, this QoS-related information must be taken into account by the
routing processes that will participate in the calculation, the
selection, the installation and the maintenance of the routes that
will comply with the aforementioned requirements. The algorithms
invoked by the routing processes take into account the cost metrics
(whose corresponding values can possibly be inferred by a DSCP
(DiffServ Code Point, [13]) value) that have been assigned by the
network administrators.
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This metric-related information is called the "TE"-related
information within the context of this draft.
Thus, this draft makes a distinction between QoS-related information
and TE-related information, where:
- QoS-related information is negotiated between customers and
service providers,
- TE-related configuration information is dynamically provided to
routers, and is exchanged between routers so that they can
compute, select, install, and maintain the (traffic-engineered)
routes accordingly.
From this perspective, QoS-related information provides information
on the traffic (both unicast and multicast) to be forwarded in the
network (such as source address, destination address, protocol
identification, DSCP marking, etc.), whereas TE-related information
provides information for the routing processes that will indicate the
routers of the network how to forward the aforementioned traffic,
i.e. compute and select the routes that will convey such traffic.
Given these basic assumptions, this draft aims at specifying a COPS-
based TE client-type that has the following characteristics:
- The TE client-type is supported by the PEP (Policy Enforcement
Point) capability that allows a router to enforce a collection of
policies, thanks to a COPS communication that has been established
between the PEP and the PDP,
- The actual enforcement of an IP routing/TE policy is based upon
the TE-related configuration information that will be exchanged
between the PDP and the PEP, and that will be used by the router
for selecting, installing, maintaining and possibly withdrawing IP
TE routes.
4. The Generic Model of an IP Routing/TE Policy Enforcement Scheme
The use of the COPS protocol for dynamically enforcing an IP
routing/TE policy yields the generic model depicted in figure 1.
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+----------------+
| |
| IP Router |
| |
| +-----+ | COPS-PR +-----+ +-----------+
| | PEP |<---|-------------->| PDP |<-->| IP TE PIB |
| +-----+ | +-----+ +-----------+
| | |
| | |
| +-----+ |
| | LPDP| |
| +-----+ |
| | |
| | |
| /-------\ |
| | | |
| +-----+ +-----+|
| | RIB |.| RIB ||
| +-----+ +-----+|
| | | |
| | | |
| \-------/ |
| | |
| +-----+ |
| | FIB | |
| +-----+ |
+----------------+
Figure 1: Generic model of an IP routing/TE policy enforcement
scheme.
As depicted in figure 1, the routers embed the following components:
- A PEP capability, which supports the TE client-type. The support
of the TE client-type is notified by the PEP to the PDP, and is
unique for the area covered by the IP routing/traffic engineering
policy, so that the PEP can treat all the COPS client-types it
supports as non-overlapping and independent namespaces,
- A Local Policy Decision Point (LPDP), which can be somewhat
compared to the routing processes that have been activated in the
router. The LPDP will therefore contribute to the computation and
the selection of the IP routes (see section 6 of this draft),
- Several instances of Routing Information Bases (RIB), according to
the different (unicast and multicast) routing processes that have
been activated - one can easily assume the activation of at least
one IGP (Interior Gateway Protocol, like OSPF) and BGP4,
- Conceptually one Forwarding Information Base (FIB), which will
store the routes that have been selected by the routing processes,
but this draft makes no assumption about the number of FIBs that
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can be supported by a router (e.g. within the context of an IP VPN
(Virtual Private Network) service offering).
As suggested in [14], the enforcement of an IP routing/traffic
engineering policy is based upon the use of a policy server (the PDP
in the above figure) that sends IP TE-related information towards the
PEP capability embedded in the IP router.
The TE-related information is stored and maintained in an TE Policy
Information Base ([15]), which will be accessed by the PDP to
retrieve and update the TE-related information whenever necessary
(see section 6 of this draft).
Also, this TE-related information is conveyed between the PDP and the
PEP thanks to the establishment of a COPS-PR connection between these
two entities. The COPS-PR protocol assumes a named data structure
(the PIB), so as to identify the type and purpose of the policy
information that is sent by the PDP to the PEP for the provisioning
of a given policy.
Within the context of this draft, the data structure of the PIB
refers to the IP routing/TE policy that is described in the PIB as a
collection of PRovisioning Classes (PRC). Furthermore, these classes
contain attributes that actually describe the TE-related policy
provisioning data that will be sent by the PDP to the PEP. Some of
these attributes consist of the link and traffic engineering metrics
that will be manipulated by the routing processes being activated in
the routers to compute the IP routes.
The TE classes are instantiated as multiple PRI (PRovisioning
Instance) instances, each of which being identified by PRovisioning
Instance iDentifier (PRID). A given PRI specifies the data content
carried in the TE client specific objects. A TE PRI typically
contains a value for each attribute that has been defined for the TE
PRC.
Currently, the TE PIB has identified a per-DSCP TE PRC instantiation
scheme, because the DSCP value conveyed in each IP datagram that will
be processed by the routers privileges the notion of "DSCP-based"
routing. Such a routing scheme aims at reflecting the IP routing/TE
policies that have been defined by a service provider, assuming a
restricted number of DSCP-identified classes of service that will
service the customers' requirements.
5. TE Client-Type Specific Information to be Carried in COPS Messages
This section describes the formalism that is specific to the use of a
TE client-type, given that only the COPS messages that require a TE
client-type specific definition are described in this section, i.e.
the other COPS messages to be exchanged between a PEP that supports
the TE client-type and a PDP, and which do not need to carry TE
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client-type specific information, are those described in the
corresponding [2] and [3] documents, without any further elaboration.
It must be noted that, whatever the contents of the COPS messages
that MAY be exchanged between the PEP supporting the TE client-type
and the PDP, the actual calculation, selection, installation,
maintenance and possible withdrawal of IP routes in the router's FIB
is left to the routers.
Nevertheless, the information contained in the router's FIB MUST be
consistent with the information contained in the TE PIB: this is done
thanks to the synchronization features of the COPS architecture, as
defined in [2].
5.1. Client-Type Field of the Common Header of Every COPS Message
All of the TE client-type COPS messages MUST contain the COPS Common
Header with the 2-byte encoded Client-Type field valued with the yet-
to-be assigned IANA number (see section 7 of this draft) for the TE
client-type.
5.2. COPS Message Content
5.2.1. Request Messages (REQ)
The REQ message is sent by the TE client-type to issue a
configuration request to the PDP, as specified in the COPS Context
Object. The REQ message includes the current configuration
information related to the enforcement of an IP routing/TE policy.
Such configuration information is encoded according to the ClientSI
format that is defined for the Named ClientSI object of the REQ
message.
The configuration information is encoded as a collection of bindings
that associate a PRID object and an Encoded Provisioning Instance
Data (EPD).
Such information MAY consist of:
- The identification information of the router, e.g. the
identification information that is conveyed in OSPF LSA (Link
State Advertisement) Type 1 messages. The use of a loopback
interface's IP address is highly recommended for the instantiation
of the corresponding EPD,
- The link metric values that have been currently assigned to each
(physical/logical) interface of the router, as described in [4]
for example. Such values MAY vary with an associated DSCP value,
i.e. the link metric assigned to an interface is a function of the
DSCP value encoded in each IP datagram that this router may have
to forward,
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- The traffic engineering metric values that specify the link metric
values for traffic engineering purposes, as defined in [7], for
example. These values MAY be different from the above-mentioned
link metric values and they MAY also vary according to DSCP
values.
5.2.2. Decision Messages (DEC)
The DEC messages are used by the PDP to send TE policy provisioning
data to the TE client-type. DEC messages are sent in response to a
REQ message received from the PEP, or they can be unsolicited, e.g.
subsequent DEC messages can be sent at any time after, to supply the
PEP with additional or updated TE policy configuration information
without the solicited message flag set in the COPS message header,
since such messages correspond to unsolicited decisions.
DEC messages typically consist of "install" and/or "remove"
decisions, and, when there is no Decision Flags set, the DEC message
includes the Named Decision Data (Provisioning) object.
Apart from the aforementioned identification information, and
according to the kind of (PRID, EPD) bindings that MAY be processed
by the PEP (see section 5.2.1. of the draft), DEC messages MAY refer
to the following decision examples:
- Assign new link/traffic engineering metric values each time a new
interface is installed/created on the router. These new values
will obviously yield the generation of LSA messages in the case of
the activation of the OSPF protocol, and/or the generation of BGP4
UPDATE messages (e.g. in the case of a new instantiation of the
MULTI_EXIT_DISC (MED) attribute). This will in turn yield the
computation of (new) IP routes that MAY be installed in the
router's FIB,
- Modify previously assigned metric values, thanks to a
remove/install decision procedure (this may yield a modification
of the router's FIB as well, obviously),
- Remove assigned metric values, e.g. the corresponding interfaces
may not be taken into consideration by the routing algorithms
anymore (or during a specific period of time, e.g. for maintenance
purposes).
5.2.3. Report Messages (RPT)
The Report message allows the PEP to notify the PDP with a particular
set of IP routing/TE policy provisioning instances that have been
successfully or unsuccessfully installed/removed.
When the PEP receives a DEC message from the PDP, it MUST send back a
RPT message towards the PDP. The RPT message will contain one of the
following Report-Types:
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"Failure": Notification of errors that occurred during the
processing of the (PRID, EPD) bindings contained in
the DEC message. Such a notification procedure can
include a failure report in assigning an updated value
of a given metric for example,
"Success": Notification of successful assignment of metric
values, and/or successful installation of IP routes in
the router's FIB. From this perspective, there MAY be
routes that will be installed in the router's FIB
without any explicit decision sent by the PDP to the
PEP regarding the calculation/installation of the
aforementioned route. This typically reflects a normal
dynamic routing procedure, whenever route
advertisement messages are received by the router,
including messages related to a topology change. In
any case (i.e. whatever the effect that yielded the
installation of a route in the router's FIB), a RPT
message MUST be sent by the PEP towards the PDP to
notify such an event, so that the TE PIB will be
updated by the PDP accordingly.
"Accounting": The accounting RPT message will carry statistical
information related to the traffic that will transit
through the router. This statistical information MAY
be used by the PDP to possibly modify the metric
values that have been assigned when thresholds have
been crossed: for example, if the RPT message reports
that x % of the available rate associated to a given
interface have been reached, then the PDP MAY send an
unsolicited DEC message in return, so that potential
bottlenecks be avoided.
5.3. Backward Compatibility Issues
In the case where the IP network is composed of COPS-aware routers
(which embed a PEP capability that supports the TE client-type), as
well as COPS-unaware routers, the activation of a link state routing
protocol (like OSPF) together with the reporting mechanism that has
been described in section 5.2. of this draft addresses the backward
compatibility issue.
Indeed, the flooding mechanism that is used by the OSPF protocol for
the propagation of the LSA messages assumes that, in particular, the
COPS-aware routers will receive these update messages. Upon receipt
of such messages, the PEP will have the ability to notify the PDP
with the corresponding changes (e.g. by using a "Success" report-type
that will reflect the installation of new routes in the router's
FIB), so that the TE PIB can be updated accordingly.
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The same observation can be made within the context of the activation
of the BGP4 protocol, because of the iBGP full-mesh topology that is
required to allow the routers of a given domain to get a homogeneous
view of the "outside" world.
6. COPS-PR Usage of the TE Client-Type
After having opened a COPS connection with the PDP, the PEP sends a
REQ message towards the PDP that will contain a Client Handle. The
Client Handle is used to identify a specific request state associated
to the TE client-type supported by the PEP. The REQ message will
contain a "Configuration Request" context object.
This REQ message will also carry the named client specific
information (including the (default) configuration information), as
described in section 5.2.1.of the draft. Default configuration
information includes the information available during the bootstrap
procedures of the routers.
The routes that have been installed in the router's FIB MAY be
conveyed in specific (PRID, EPD) bindings in the REQ message as well.
Upon receipt of the REQ message, the PDP will send back a DEC message
towards the PEP. This DEC message will carry TE Named Decision Data
object that will convey all the appropriate installation/removal of
(PRID, EPD), as described in section 5.2.2 of this draft. One of the
basic goals of this named Decision objects consists in making the
routers enforce a given IP routing/TE policy.
Upon receipt of a DEC message, the TE-capable PEP will (try to) apply
the corresponding decisions, by making the network device (and its
associated implementation-specific Command Line Interface, if
necessary) install the named TE policy data (e.g. assign a metric
value to a recently-installed interface).
Then, the PEP will notify the PDP about the actual enforcement of the
named TE policy decision data, by sending the appropriate RPT message
back to the PDP. Depending on the report-type that will be carried in
the RPT message, the contents of the message MAY include:
- Successfully/unsuccessfully assigned new/updated metric values,
- Successfully installed routes from the router's FIB. Note that the
notion of "unsuccessfully installed routes" is meaningless,
- Successfully/unsuccessfully withdrawn routes from the router's
FIB. Route withdrawal is not only subject to the normal IGP and
BGP4 procedures (thus yielding the generation of the corresponding
advertisement messages), but also subject to named TE policy
decision data (carried in a specific DEC message), like those data
related to the lifetime of a service.
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The RPT message MAY also carry the "Accounting" report-type, as
described in section 5.2.3.of this draft.
7. IANA Considerations
Section 5.1 of this draft has identified the need for the assignment
of a specific number that will uniquely identify the TE client-type
in every COPS message to be exchanged between a PEP and a PDP.
This value SHOULD be chosen in the range of 0x8000 - 0xFFFF,according
to a First Come First Served policy, as mentioned in both [2] and
[16].
8. Security Considerations
This draft specifies a new client-type that will make use of the COPS
protocol for the provisioning and the enforcement of IP routing/TE
policies. As such, it introduces no new security issues over the COPS
protocol itself, or its usage for policy provisioning.
Nevertheless, it is recommended that the TE client-type
systematically uses the Message Integrity Object (Integrity) for the
authentication and the validation of every COPS message it may
exchange with the PDP with whom it has established a COPS
communication. The Message Integrity Object also prevents from replay
attacks.
In addition, the IP Security ([17]) protocol suite may be activated,
and the IPSec Authentication Header (AH) should be used for the
validation of the COPS connection, while the Encapsulated Security
Payload (ESP) may be used to provide both validation and secrecy, as
stated in [2].
9. References
[1] Bradner, S.,"The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
[2] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja R., Sastry
A., "The COPS (Common Open Policy Service) Protocol", RFC 2748,
January 2000.
[3] Ho Chan, K., Durham, D., Gai, S., Herzog, S., McLoghrie, K.,
Reichmeyer, F., Seligson, J., Smith, A., Yavatkar, R., "COPS Usage
for Policy Provisioning (COPS-PR)", RFC 3084, March 2001.
[4] Moy, J.,"OSPF Version 2", RFC 2328, April 1998.
[5] Rekhter, Y., Li T., "A Border Gateway Protocol 4 (BGP-4)", RFC
1771, March 1995.
[6] Jacquenet, C., Proust, C., "An Introduction to IP Multicast
Traffic Engineering", Proceedings of the ECUMN 2002 conference.
See http://iutsun1.colmar.uha.fr/ECUMN02.html for further details.
[7] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
Extensions to OSPF", RFC 3630, September 2003.
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[8] Smit, H., Li T., "IS-IS Extensions for Traffic Engineering",
draft-ietf-isis-traffic-05.txt, Work in Progress, August 2003.
[9] ISO/IEC 10589, "Intermediate System to Intermediate System,
Intra-Domain Routing Exchange Protocol for use in Conjunction with
the Protocol for Providing the Connectionless-mode Network Service
(ISO 8473)", June 1992.
[10] Jacquenet, C., Cristallo, G., "The BGP QOS_NLRI Attribute",
draft-jacquenet-bgp-qos-00.txt, Work in Progress, February 2004.
[11] Yavatkar, R., Pendarakis, D., Guerin, R., "A Framework for
Policy-Based Admission Control", RFC 2753, January 2000.
[12] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[13] Nichols K., Blake S., Baker F., Black D., "Definition of the
Differentiated Services Field (DS Field) in the IPv4 and IPv6
Headers", RFC 2474, December 1998.
[14] Apostopoulos G., Guerin R., Kamat S., Tripathi S. K., "Server
Based QOS Routing", Proceedings of the 1999 GLOBCOMM Conference.
[15] Boucadair, M., Jacquenet, C., "An IP Forwarding Policy
Information Base", draft-jacquenet-fwd-pib-00.txt, Work in
Progress, February 2004.
[16] Alvestrand H., Narten T., "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[17] Atkinson R., "Security Architecture for the Internet Protocol",
RFC 2401, August 1998.
10. Acknowledgments
Part of this work is funded by the European Commission, within the
context of the MESCAL (Management of End-to-End Quality of Service
Across the Internet At Large, http://www.mescal.org) project, which
is itself part of the IST (Information Society Technologies) research
program.
The author would also like to thank all the partners of the MESCAL
project for the fruitful discussions that have been conducted so far
within the context of the traffic engineering specification effort of
the project, as well as MM. Boucadair and Brunner for their valuable
input.
11. Author's Address
Christian Jacquenet
France Telecom
3, avenue Fran‡ois Ch‚teau
CS 36901
35069 Rennes CEDEX
France
Phone: +33 2 99 87 63 31
Email: christian.jacquenet@francetelecom.com
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12. Full Copyright Statement
Copyright(C) The Internet Society (2004). All Rights Reserved.
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or assist its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
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The limited permissions granted above are perpetual and will not be
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Network Working Group M. Boucadair
Internet Draft C. Jacquenet
Document: draft-jacquenet-fwd-pib-00.txt France Telecom
Category: Experimental February 2004
Expires August 2004
An IP Forwarding Policy Information Base
<draft-jacquenet-fwd-pib-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 [1].
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This draft specifies a set of Policy Rule Classes (PRC) for the
enforcement of an IP forwarding policy by network devices. Instances
of such classes reside in a virtual information store, which is
called the IP Forwarding Policy Information Base (PIB). The
corresponding IP forwarding policy provisioning data are intended for
use by a COPS-PR TE Client-Type, and they complement the PRC classes
that have been defined in the Framework PIB.
Table of Contents
1. Introduction...............................................2
2. Conventions used in this document..........................3
3. PIB Overview...............................................3
4. The IP Forwarding Policy Information Base..................4
5. Security Considerations....................................9
6. References.................................................9
7. Acknowledgments...........................................10
8. Authors' Addresses........................................10
9. Full Copyright Statement..................................11
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1. Introduction
The deployment of value-added IP services over the Internet has
become one of the most competing challenges for service providers, as
well as a complex technical issue.
Within the context of network resource provisioning and allocation,
the Common Open Policy Service protocol (COPS, [2]) and its usage for
the support of Policy Provisioning ([3]) is one of the most promising
candidate protocols that should help service providers in dynamically
enforcing IP routing and traffic engineering policies.
An IP routing/TE policy consists in appropriately provisioning and
allocating/de-allocating the switching and the transmission resources
of an IP network (i.e. the routers and the links that connect these
routers, respectively), according to e.g. rate, one-way delay, inter-
packet delay variation, etc.) that have been possibly negotiated
between the customers and the service providers, and according to (a
set of)routing metrics, which can also reflect the network
conditions.
Thus, the enforcement of IP routing/TE policies yields the need for
an introduction of a high level of automation for the dynamic
provisioning of the configuration data that will be taken into
account by the routers to select the appropriate IP routes.
Within the context of this document, the actual enforcement of an IP
forwarding policy is primarily based upon the activation of both
intra- and inter-domain dynamic routing protocols that will be
activated by the routers to select, install, maintain and possibly
withdraw IP routes.
Such routes have been selected so that they comply as much as
possible with the aforementioned QoS requirements and/or specific
routing constraints, possibly depending on the type of traffic that
will be conveyed along these routes.
It is therefore necessary to provide the route selection processes
with the information that will depict the routing policies that are
to be enforced within a domain and, whenever appropriate, the
aforementioned constraints and metrics, given the dynamic routing
protocols actually support traffic engineering capabilities for the
calculation and the selection of such routes.
Some of these capabilities are currently being specified in [4] and
[5] for the OSPF (Open Shortest Path First) and the IS-IS
(Intermediate System to Intermediate System routing protocol, [6])
interior routing protocols respectively, while there is a comparable
effort for the BGP4 (Border Gateway Protocol, version 4) protocol, as
described in [7], for example.
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To provide the route selection processes with the aforementioned
information, one possibility is to use the COPS-PR protocol, together
with a collection of policy provisioning data that will be stored in
a virtual information store, called a Policy Information Base.
This draft describes a collection of Policy Rule Classes that will be
stored and dynamically maintained in an IP forwarding PIB. The "rule"
and "role" concepts, which have been defined in [8], are adopted by
this document to distribute the IP routing policy provisioning data
over the COPS-PR protocol.
The corresponding IP forwarding policy provisioning data are intended
for use by a COPS-PR TE Client-Type ([9]), and they complement the
PRC classes that have been defined in the Framework PIB ([10]).
This document is organized as follows:
- Section 3 provides an overview of the organization of the IP
forwarding PIB,
- Section 4 provides a description of the PRC classes of the IP
forwarding PIB, according to the semantics of the Structure of
Policy Provisioning Information (SPPI, [11]).
2. Conventions used in this document
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 [12].
3. PIB Overview
The dynamic enforcement of an IP forwarding policy relies upon the
activation of intra- and inter-domain routing protocols that will
have the ability to take into account configuration information for
the computation and the selection of routes, which will comply as
much as possible with the constraints and requirements that MAY have
been contractually defined between customers and service providers.
This document specifies an IP forwarding PIB that mainly aims at
storing and maintaining the information related to the IP routes that
have been installed in the routers' Forwarding Information Bases, so
that service providers maintain and update the adequate knowledge of
the network's resources availability, from an IP routing perspective.
As such, this PIB has been designed so that it SHOULD be gracefully
complemented by PIB modules that will reflect the IGP- and BGP-
inferred routing policies to be enforced, in terms of cost metrics'
values to be assigned and updated whenever needed.
Also, the accounting PIB module which is described in [13] aims at
providing the most accurate feedback (to service providers) on how
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efficient the enforcement of a given IP forwarding policy (as
specified in this document) actually is.
The choice of this PIB organization is basically twofold:
- Make the PIB implementation simple,
- Provide the appropriate granularity of policy provisioning data
that will be manipulated according to the requirements and
technical choices of service providers.
Therefore, the IP forwarding PIB is currently organized into the
following provisioning classes:
1. The Forwarding Classes (ipFwdClasses): the information
contained in these classes is meant to provide a detailed
description of the IP routes as they have been selected by the
routers of a given domain,
2. The Statistics Classes (ipFwdStatsClasses): the information
contained in these classes is meant to provide statistics on
the use of the IP routes currently depicted in the IP
forwarding PIB.
4. The IP Forwarding Policy Information Base
IP-FWD-PIB PIB-DEFINITIONS ::= BEGIN
IMPORTS
Unsigned32, Integer32, MODULE-IDENTITY,
MODULE-COMPLIANCE, OBJECT-TYPE, OBJECT-GROUP
FROM COPS-PR-SPPI
InstanceId, ReferenceId, Prid, TagId
FROM COPS-PR-SPPI-TC
InetAddress, InetAddressType
FROM INET-ADDRESS-MIB
Count, TEXTUAL-CONVENTION
FROM ACCT-FR-PIB-TC
TruthValue, TEXTUAL-CONVENTION
FROM SNMPv2-TC
RoleCombination, PrcIdentifier
FROM FRAMEWORK-ROLE-PIB
SnmpAdminString
FROM SNMP-FRAMEWORK-MIB;
ipFwdPib MODULE-IDENTITY
SUBJECT-CATEGORIES { tbd } -- TE client-type to be
-- assigned by IANA
LAST-UPDATED "200301220900Z"
ORGANIZATION "France Telecom"
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CONTACT-INFO "
Mohamed Boucadair
France Telecom R & D
42, rue des Coutures
BP 6243
14066 CAEN CEDEX 04
France
Phone: +33 2 31 75 92 31
E-Mail: mohamed.boucadair@francetelecom.com"
DESCRIPTION
"The PIB module containing a set of policy rule classes
that describe the IP routes that have been computed by
means of routing/TE policy enforcement, as well as
route traffic statistics."
REVISION "200402041000Z"
DESCRIPTION
"Initial version."
::= { pib tbd } -- tbd to be assigned by IANA
ipFwdClasses OBJECT IDENTIFIER ::= { ipFwdPib 1 }
ipFwdStatsClasses OBJECT IDENTIFIER ::= { ipFwdPib 2 }
--
-- Forwarding classes. The information contained in these classes
-- is meant to provide a detailed description of the available IP
-- routes. One table has been specified so far, but there is room
-- for depicting different kinds of routes, like MPLS (MultiProtocol
-- Label Switching, ([14]) LSP (Label switched Paths) paths.
--
--
--
--
-- The ipFwdTable
--
ipFwdTable OBJECT-TYPE
SYNTAX SEQUENCE OF ipRouteEntry
PIB-ACCESS notify
STATUS current
DESCRIPTION
"This table describes the IP routes that are installed
in the forwarding tables of the routers."
::= { ipFwdClasses 1 }
ipRouteEntry OBJECT-TYPE
SYNTAX ipRouteEntry
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STATUS current
DESCRIPTION
"A particular route to a particular destination."
PIB-INDEX { ipRoutePrid }
UNIQUENESS { ipRouteDest,
ipRouteMask,
ipRoutePhbId,
ipRouteNextHopAddress
ipRouteNextHopMask
ipRouteIfIndex }
::= { ipFwdTable 1 }
ipRouteEntry ::= SEQUENCE {
ipRoutePrid InstanceId,
ipRouteDestAddrType InetAddressType,
ipRouteDest InetAddress,
ipRouteMask Unsigned32,
ipRouteNextHopAddrType InetAddressType,
ipRouteNextHopAddress InetAddress,
ipRouteNextHopMask Unsigned32,
ipRoutePhbId Integer32,
ipRouteOrigin Integer32,
ipRouteIfIndex Unsigned32
}
ipRoutePrid OBJECT-TYPE
SYNTAX InstanceId
STATUS current
DESCRIPTION
"An integer index that uniquely identifies this route
entry among all the route entries."
::= { ipRouteEntry 1 }
ipRouteDestAddrType OBJECT-TYPE
SYNTAX InetAddressType
STATUS current
DESCRIPTION
"The address type enumeration value ([15]) used to
specify the type of a route's destination IP address."
::= { ipRouteEntry 2 }
ipRouteDest OBJECT-TYPE
SYNTAX InetAddress
STATUS current
DESCRIPTION
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"The IP address to match against the packet's
destination address."
::= { ipRouteEntry 3 }
ipRouteMask OBJECT-TYPE
SYNTAX Unsigned32 (0..128)
STATUS current
DESCRIPTION
"Indicates the length of a mask for the matching of the
destination IP address. Masks are constructed by
setting bits in sequence from the most-significant bit
downwards for ipRouteMask bits length. All other bits
in the mask, up to the number needed to fill the length
of the address ipRouteDest are cleared to zero. A zero
bit in the mask then means that the corresponding bit
in the address always matches."
::= { ipRouteEntry 4 }
ipRouteNextHopAddrType OBJECT-TYPE
SYNTAX InetAddressType
STATUS current
DESCRIPTION
"The address type enumeration value used to specify the
type of the next hop's IP address."
::= { ipRouteEntry 5 }
ipRouteNextHopAddress OBJECT-TYPE
SYNTAX InetAddress
STATUS current
DESCRIPTION
"On remote routes, the address of the next router en
route; Otherwise, 0.0.0.0."
::= { ipRouteEntry 6 }
ipRouteNextHopMask OBJECT-TYPE
SYNTAX Unsigned32 (0..128)
STATUS current
DESCRIPTION
"Indicates the length of a mask for the matching of the
next hop's IP address. Masks are constructed by setting
bits in sequence from the most-significant bit
downwards for ipRouteNextHopMask bits length. All other
bits in the mask, up to the number needed to fill the
length of the address ipRouteNextHop are cleared to
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zero. A zero bit in the mask then means that the
corresponding bit in the address always matches."
::= { ipRouteEntry 7 }
ipRoutePhbId OBJECT-TYPE
SYNTAX Integer32 (-1 | 0..63)
STATUS current
DESCRIPTION
"The binary encoding that uniquely identifies a Per Hop
Behaviour (PHB, [16]) or a set of PHBs associated to
the DiffServ Code Point (DSCP) marking of the IP
datagrams that will be conveyed along this route. A
value of -1 indicates that a specific PHB ID value has
not been defined, and thus, all PHB ID values are
considered a match."
::= { ipRouteEntry 8 }
ipRouteOriginOBJECT-TYPE
SYNTAX INTEGER {
OSPF (0)
IS-IS (1)
BGP (2)
STATIC (3)
OTHER (4)
}
STATUS current
DESCRIPTION
"The value indicates the origin of the route. Either
the route has been computed by OSPF, by IS-IS,
announced by BGP4, is static, or else."
::= { ipRouteEntry 9 }
ipRouteIfIndex OBJECT-TYPE
SYNTAX Unsigned32 (0..65535)
STATUS current
DESCRIPTION
"The ifIndex value that identifies the local interface
through which the next hop of this route is
accessible."
::= { ipRouteEntry 10 }
--
-- Route statistics classes. The information contained
-- in the yet-to-be defined tables aim at reporting statistics about
-- COPS control traffic, route traffic and potential errors. The
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-- next version of the draft will provide a first table that will be
-- based upon the use of the "count" clause.
--
--
END
5. Security Considerations
The traffic engineering policy provisioning data as they are
described in this PIB will be used for configuring the appropriate
network elements that will be involved in the dynamic enforcement of
the corresponding routing and traffic engineering policies, by means
of a COPS-PR communication that will convey this information.
The function of dynamically provisioning network elements with such
configuration information implies that only an authorized COPS-PR
communication takes place.
From this perspective, this draft does not introduce any additional
security issues other than those that have been identified in the
COPS-PR specification, and it is therefore recommended that the IPSec
([17]) protocol suite be used to secure the above-mentioned
authorized communication.
6. References
[
[1] Bradner,] S., "The Internet Standards Process -- Revision 3",
BCP 9, RFC 2026, October 1996.
[2] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja R., Sastry
A., "The COPS (Common Open Policy Service) Protocol", RFC 2748,
Proposed Standard, January 2000.
[3] Ho Chan, K., Durham, D., Gai, S., Herzog, S., McLoghrie, K.,
Reichmeyer, F., Seligson, J., Smith, A., Yavatkar, R., "COPS Usage
for Policy Provisioning (COPS-PR)", RFC 3084, March 2001.
[4] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
Extensions to OSPF", RFC 3630, September 2003.
[5] Smit, H., Li, T., "IS-IS Extensions for Traffic Engineering",
draft-ietf-isis-traffic-05.txt, Work in Progress, August 2003.
[6] ISO/IEC 10589, "Intermediate System to Intermediate System,
Intra-Domain Routing Exchange Protocol for use in Conjunction with
the Protocol for Providing the Connectionless-mode Network Service
(ISO 8473)", June 1992.
[7] Jacquenet, C., "The BGP QOS_NLRI Attribute", draft-jacquenet-
bgp-qos-00.txt, Work in Progress, February 2004.
[8] Moore, B. et al., "Policy Core Information Model -- Version 1
Specification", RFC 3060, February 2001.
[9] Jacquenet, C., "A COPS Client-Type for Traffic Engineering",
draft-jacquenet-cops-te-00.txt, Work in Progress, February 2004.
Jacquenet et al. Experimental - Expires August 2004 [Page 9]
Internet Draft An IP Forwarding PIB February 2004
[10] Sahita, R., et al., "Framework Policy Information Base", RFC
3318, March 2003.
[11] McLoghrie, K., et al., "Structure of Policy Provisioning
Information (SPPI)", RFC 3159, August 2001.
[12] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
[13] Boucadair, M., "An IP TE PIB for Accounting purposes", draft-
boucadair-ipte-acct-pib-02.txt, Work in Progress, June 2003.
[14] Rosen, E., et al., "Multiprotocol Label Switching Architecture",
RFC 3031, January 2001.
[15] Daniele, M., Haberman, B., Routhier, S., Schoenwaelder, J.,
"Textual Conventions for Internet Network Addresses", RFC 3291,
May 2002.
[16] Black, D., Brim, S., Carpenter, B., Le Faucheur, F., "Per Hop
Behaviour Identification Codes", RFC 3140, June 2001.
[17] Kent, S., Atkinson, R., "Security Architecture for the Internet
Protocol", RFC 2401, November 1998.
7. Acknowledgments
Part of this work is funded by the European Commission, within the
context of the MESCAL (Management of End-to-End Quality of Service
Across the Internet At Large, http://www.mescal.org) project, which
is itself part of the IST (Information Society Technologies) research
program.
The authors would also like to thank all the partners of the MESCAL
project for the fruitful discussions that have been conducted so far
within the context of the traffic engineering specification effort of
the project.
8. Authors' Addresses
Mohamed Boucadair
France Telecom R & D
DMI/SIR
42, rue des Coutures
BP 6243
14066 Caen Cedex 4
France
Phone: +33 2 31 75 92 31
Email: mohamed.boucadair@francetelecom.com
Christian Jacquenet
France Telecom
3, avenue Fran‡ois Ch‚teau
CS 36901
35069 Rennes CEDEX
France
Phone: +33 2 99 87 63 31
Email: christian.jacquenet@francetelecom.com
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9. Full Copyright Statement
Copyright (C) The Internet Society (2004). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist its implementation may be prepared, coed, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Jacquenet et al. Experimental - Expires August 2004 [Page 11]
Network Working Group G. Cristallo
Internet Draft Alcatel
Document: draft-jacquenet-bgp-qos-00.txt C. Jacquenet
Category: Experimental France Telecom
Expires August 2004 February 2004
The BGP QOS_NLRI Attribute
<draft-jacquenet-bgp-qos-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 [1].
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet Drafts as reference
material or to cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
NOTE: a PDF version of this document (which includes the figures
mentioned in section 7) can be accessed at http://www.mescal.org.
Abstract
This draft specifies an additional BGP4 (Border Gateway Protocol,
version 4) attribute, named the "QOS_NLRI" attribute, which aims at
propagating QoS (Quality of Service)-related information associated
to the NLRI (Network Layer Reachability Information) information
conveyed in a BGP UPDATE message.
Table of Contents
1. Conventions Used in this Document..........................2
2. Introduction...............................................2
3. Basic Requirements.........................................3
4. The QOS_NLRI Attribute (Type Code tbd*)....................3
5. Operation..................................................7
6. Use of Capabilities Advertisement with BGP-4...............8
7. Simulation Results.........................................8
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7.1. A Phased Approach..........................................8
7.2. A Case Study..............................................10
7.3. Additional Results........................................11
7.4. Next Steps................................................12
8. IANA Considerations.......................................12
9. Security Considerations...................................12
10. References................................................13
11. Acknowledgments...........................................13
12. Authors' Addresses........................................14
13. Full Copyright Statement..................................14
1. Conventions Used in this Document
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 [2].
2. Introduction
Providing end-to-end quality of service is one of the most important
challenges of the Internet, not only because of the massive
development of value-added IP service offerings, but also because of
the various QoS policies that are currently enforced within an
autonomous system, and which may well differ from one AS (Autonomous
System) to another.
For the last decade, value-added IP service offerings have been
deployed over the Internet, thus yielding a dramatic development of
the specification effort, as far as quality of service in IP networks
is concerned. Nevertheless, providing end-to-end quality of service
across administrative domains still remains an issue, mainly because:
- QoS policies may dramatically differ from one service provider to
another,
- The enforcement of a specific QoS policy may also differ from one
domain to another, although the definition of a set of common
quality of service indicators may be shared between the service
providers.
Activate the BGP4 protocol ([3]) for exchanging reachability
information between autonomous systems has been a must for many
years. Therefore, disseminating QoS information coupled with
reachability information in a given BGP UPDATE message appears to be
helpful in enforcing an end-to-end QoS policy.
This draft aims at specifying a new BGP4 attribute, the QOS_NLRI
attribute, which will convey QoS-related information associated to
the routes described in the corresponding NLRI field of the
attribute.
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This document is organized according to the following sections:
- Section 3 describes the basic requirements that motivate the
approach,
- Section 4 describes the attribute,
- Section 5 elaborates on the mode of operation,
- Section 6 elaborates on the use of the capabilities advertisement
feature of the BGP4 protocol,
- Section 7 depicts the results of a simulation work,
- Finally, sections 8 and 9 introduce IANA and some security
considerations, respectively.
3. Basic Requirements
The choice of using the BGP4 protocol for exchanging QoS information
between domains is not only motivated by the fact BGP is currently
the only inter-domain (routing) protocol activated in the Internet,
but also because the manipulation of attributes is a powerful means
for service providers to disseminate QoS information with the desired
level of precision.
The approach presented in this draft has identified the following
requirements:
- Keep the approach scalable. The scalability of the approach can be
defined in many ways that include the convergence time taken by the
BGP peers to reach a consistent view of the network connectivity,
the number of route entries that will have to be maintained by a
BGP peer, the dynamics of the route announcement mechanism (e.g.,
how frequently and under which conditions should an UPDATE message
containing QoS information be sent?), etc.
- Keep the BGP4 protocol operation unchanged. The introduction of a
new attribute should not affect the way the protocol operates, but
the information contained in this attribute may very well influence
the BGP route selection process.
- Allow for a smooth migration. The use of a specific BGP attribute
to convey QoS information should not constrain network operators to
migrate the whole installed base at once, but rather help them in
gradually deploying the QoS information processing capability.
4. The QOS_NLRI Attribute (Type Code tbd*)
(*): "tbd" is subject to the IANA considerations section of this
draft.
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The QOS_NLRI attribute is an optional transitive attribute that can
be used:
1. To advertise a QoS route to a peer. A QoS route is a route that
meets one or a set of QoS requirement(s) to reach a given (set of)
destination prefixes. Such QoS requirements can be expressed in
terms of minimum one-way delay ([4]) to reach a destination, the
experienced delay variation for IP datagrams that are destined to
a given destination prefix ([5]), the loss rate experienced along
the path to reach a destination, and/or the identification of the
traffic that is expected to use this specific route
(identification means for such traffic include DSCP (DiffServ Code
Point, [6]) marking). These QoS requirements can be used as an
input for the BGP route calculation process,
2. To provide QoS-related information along with the NLRI information
in a single BGP UPDATE message. It is assumed that this
information will be related to the route (or set of routes)
described in the NLRI field of the attribute.
From a service provider's perspective, the choice of defining the
QOS_NLRI attribute as an optional transitive attribute is motivated
by the fact that this kind of attribute allows for gradual deployment
of the dissemination of QoS-related information by BGP4: not all the
BGP peers are supposed to be updated accordingly, while partial
deployment of such QoS extensions can already provide an added value,
e.g. in the case where a service provider manages multiple domains,
and/or has deployed a BGP confederation ([7]).
This draft makes no specific assumption about the means to actually
value this attribute, since this is mostly a matter of
implementation, but the reader is suggested to have a look on
document [8], as an example of a means to feed the BGP peer with the
appropriate information. The QOS_NLRI attribute is encoded as
follows:
+---------------------------------------------------------+
| QoS Information Code (1 octet) |
+---------------------------------------------------------+
| QoS Information Sub-code (1 octet) |
+---------------------------------------------------------+
| QoS Information Value (2 octets) |
+---------------------------------------------------------+
| QoS Information Origin (1 octet) |
+---------------------------------------------------------+
| Address Family Identifier (2 octets) |
+---------------------------------------------------------+
| Subsequent Address Family Identifier (1 octet) |
+---------------------------------------------------------+
| Network Address of Next Hop (4 octets) |
+---------------------------------------------------------+
| Flags (1 octet) |
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+---------------------------------------------------------+
| Identifier (2 octets) |
+---------------------------------------------------------+
| Length (1 octet) |
+---------------------------------------------------------+
| Prefix (variable) |
+---------------------------------------------------------+
The use and meaning of the fields of the QOS_NLRI attribute are
defined as follows:
- QoS Information Code:
This field carries the type of the QOS information. The following
types have been identified so far:
(0) Reserved
(1) Packet rate, i.e. the number of IP datagrams that can be
transmitted (or have been lost) per unit of time, this number
being characterized by the elaboration provided in the QoS
Information Sub-code (see below)
(2) One-way delay metric
(3) Inter-packet delay variation
(4) PHB Identifier
- QoS Information Sub-Code:
This field carries the sub-type of the QoS information. The
following sub-types have been identified so far:
(0) None (i.e. no sub-type, or sub-type unavailable, or unknown sub-
type)
(1) Reserved rate
(2) Available rate
(3) Loss rate
(4) Minimum one-way delay
(5) Maximum one-way delay
(6) Average one-way delay
The instantiation of this sub-code field MUST be compatible with the
value conveyed in the QoS Information code field, as stated in the
following table (the rows represent the QoS Information Code possible
values, the columns represent the QoS Information Sub-code values
identified so far, while the "X" sign indicates incompatibility).
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+---------------------------------------+
| | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
+---------------------------------------+
| 0 | | | | | | | |
+---------------------------------------+
| 1 | | | | | X | X | X |
+---------------------------------------+
| 2 | | X | X | X | | | |
+---------------------------------------+
| 3 | | X | X | X | X | X | X |
+---------------------------------------+
| 4 | | X | X | X | X | X | X |
+---------------------------------------+
- QoS Information Value:
This field indicates the value of the QoS information. The
corresponding units obviously depend on the instantiation of the
QoS Information Code. Namely, if:
(a) QoS Information Code field is "0", no unit specified,
(b) QoS Information Code field is "1", unit is kilobits per second
(kbps), and the rate encoding rule is composed of a 3-bit
exponent (with an assumed base of 8) followed by a 13-bit
mantissa, as depicted in the figure below:
0 8 16
| | |
-----------------
|Exp| Mantissa |
-----------------
This encoding scheme advertises a numeric value that is (2^16 -1
- exponential encoding of the considered rate), as depicted in
[9].
(c) QoS Information Code field is "2", unit is milliseconds,
(d) QoS Information Code field is "3", unit is milliseconds,
(e) QoS Information Code field is "4", no unit specified.
- QoS Information Origin:
This field provides indication on the origin of the path
information, as defined in section 4.3.of [3].
- Address Family Identifier (AFI):
This field carries the identity of the Network Layer protocol
associated with the Network Address that follows. Currently
defined values for this field are specified in [10] (see the
Address Family Numbers section of this reference document).
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- Subsequent Address Family Identifier (SAFI):
This field provides additional information about the type of the
prefix carried in the QOS_NLRI attribute.
- Network Address of Next Hop:
This field contains the IPv4 Network Address of the next router
on the path to the destination prefix, (reasonably) assuming that
such routers can at least be addressed according to the IPv4
formalism.
- Flags, Identifier, Length and Prefix fields:
These four fields actually compose the NLRI field of the QOS_NLRI
attribute, and their respective meanings are as defined in
section 2.2.2 of [11].
5. Operation
When advertising a QOS_NLRI attribute to an external peer, a router
may use one of its own interface addresses in the next hop component
of the attribute, given the external peer to which one or several
route(s) is (are) being advertised shares a common subnet with the
next hop address. This is known as a "first party" next hop
information.
A BGP speaker can advertise to an external peer an interface of any
internal peer router in the next hop component, provided the external
peer to which the route is being advertised shares a common subnet
with the next hop address. This is known as a "third party" next hop
information.
A BGP speaker that sends an UPDATE message with the QOS_NLRI
attribute has the ability to advertise multiple QoS routes, since the
Identifier field of the attribute is part of the NLRI description. In
particular, the same prefix can be advertised more than once without
subsequent advertisements that would replace previous announcements.
Since the resolution of the NEXT_HOP address that is always conveyed
in a BGP UPDATE message is left to the responsibility of the IGP that
has been activated within the domain, the best path according to the
BGP route selection process depicted in [3] SHOULD also be
advertised. As long as the routers on the path towards the address
depicted in the NEXT_HOP attribute of the message have the additional
paths depicted in the QOS_NLRI attribute, the propagation of QoS
routes within a domain where all the routers are QOS_NLRI aware
should not yield inconsistent routing.
A BGP UPDATE message that carries the QOS_NLRI MUST also carry the
ORIGIN and the AS_PATH attributes (both in eBGP and in iBGP
exchanges). Moreover, in iBGP exchanges such a message MUST also
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carry the LOCAL_PREF attribute. If such a message is received from an
external peer, the local system shall check whether the leftmost AS
in the AS_PATH attribute is equal to the autonomous system number of
the peer than sent the message. If that is not the case, the local
system shall send the NOTIFICATION message with Error Code UPDATE
Message Error, and the Error Sub-code set to Malformed AS_PATH.
Finally, an UPDATE message that carries no NLRI, other than the one
encoded in the QOS_NLRI attribute, should not carry the NEXT_HOP
attribute. If such a message contains the NEXT_HOP attribute, the BGP
speaker that receives the message should ignore this attribute.
6. Use of Capabilities Advertisement with BGP-4
A BGP speaker that uses the QOS_NLRI attribute SHOULD use the
Capabilities Advertisement procedures, as defined in [12], so that it
might be able to determine if it can use such an attribute with a
particular peer.
The fields in the Capabilities Optional Parameter are defined as
follows:
- The Capability Code field is set to N (127 < N < 256, when
considering the "Private Use" range, as specified in [13]), while
the Capability Length field is set to "1".
- The Capability Value field is a one-octet field, which contains
the Type Code of the QOS_NLRI attribute, as defined in the
introduction of section 5 of the present draft.
In addition, the multiple path advertisement capability MUST be
supported, as defined in section 2.1 of [4].
7. Simulation Results
7.1. A Phased Approach
The simulation work basically aims at qualifying the scalability of
the usage of the QOS_NLRI attribute for propagating QoS-related
information across domains.
This effort also focused on the impact on the stability of the BGP
routes, by defining a set of basic engineering rules for the
introduction of additional QoS information, as well as design
considerations for the computation and the selection of "QoS routes".
This ongoing development effort is organized into a step-by-step
approach, which consists in the following phases:
1. Model an IP network composed of several autonomous systems.
Since this simulation effort is primarily focused on the
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qualification of the scalability related to the use of the
QOS_NLRI attribute for exchanging QoS-related information
between domains, it has been decided that the internal
architecture of such domains should be kept very simple, i.e.
without any specific IGP interaction,
2. Within this IP network, there are BGP peers that are QOS_NLRI
aware, i.e. they have the ability to process the information
conveyed in the attribute, while the other routers are not: the
latter do not recognize the QOS_NLRI attribute by definition,
and they will forward the information to other peers, by setting
the Partial bit in the attribute, meaning that the information
conveyed in the message is incomplete. This approach contributes
to the qualification of a progressive deployment of QOS_NLRI-
aware BGP peers,
3. As far as QOS_NLRI aware BGP peers are concerned, they will
process the information contained in the QOS_NLRI attribute to
possibly influence the route decision process, thus yielding the
selection (and the announcement) of distinct routes towards a
same destination prefix, depending on the QoS-related
information conveyed in the QOS_NLRI attribute,
4. Modify the BGP route decision process: at this stage of the
simulation, the modified decision process relies upon the one-
way delay information (which corresponds to the QoS Information
Code field of the attribute valued at "2"), and it also takes
into account the value of the Partial bit of the attribute.
Once the creation of these components of the IP network has been
completed (together with the modification of the BGP route selection
process), the behavior of a QOS_NLRI-capable BGP peer is as follows.
Upon receipt of a BGP UPDATE message that contains the QOS_NLRI
attribute, the router will first check if the corresponding route is
already stored in its local RIB, according to the value of the one-
way delay information contained in both QoS Information Code and Sub-
code fields of the attribute.
If not, the BGP peer will install the route in its local RIB.
Otherwise (i.e. an equivalent route already exists in its database),
the BGP peer will select the best of both routes according to the
following criteria:
- If both routes are said to be either incomplete (Partial bit has
been set) or complete (Partial bit is unset), the route with the
lowest delay will be selected,
- Otherwise, a route with the Partial bit unset is always preferred
over any other route, even if this route reflects a higher transit
delay.
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If ever both Partial bit and transit delay information are not
sufficient to make a decision, the standard BGP decision process
(according to the breaking ties mechanism depicted in [3]) is
performed.
7.2. A Case Study
REMINDER: a PDF version of this document (which includes the figures
mentioned in this section) can be accessed at http://www.mescal.org.
As stated in the previous section 7.1, the current status of the
simulation work basically relies upon the one-way transit delay
information only, as well as the complete/incomplete indication of
the Partial bit conveyed in the QOS_NLRI attribute.
The following figures depict the actual processing of the QoS-related
information conveyed in the QOS_NLRI attribute, depending on whether
the peer is QOS_NRLI-aware or not.
[Fig. 1: A Case Study.]
Figure 1 depicts the IP network that has been modelled, while figure
2 depicts the propagation of a BGP UPDATE message that contains the
QOS_NLRI attribute, in the case where the contents of the attribute
are changed, because of complete/incomplete conditions depicted by
the Partial bit of the QOS_NLRI attribute.
[Fig. 2: Propagation of One-way Delay Information via BGP4.]
Router S in figure 2 is a QOS_NRLI-capable speaker. It takes 20
milliseconds for node S to reach network 192.0.20.0: this information
will be conveyed in a QOS_NLRI attribute that will be sent by node S
in a BGP UPDATE message with the Partial bit of the QOS_NLRI
attribute unset.
Router A is another QOS_NLRI BGP peer, and it takes 3 milliseconds
for A to reach router S. Node A will update the QoS-related
information of a QOS_NLRI attribute, indicating that, to reach
network 192.0.20.0, it takes 23 milliseconds. Router A will install
this new route in its database, and will propagate the corresponding
UPDATE message to its peers.
On the other hand, router B is not capable of processing the
information conveyed in the QOS_NLRI attribute, and it will therefore
set the Partial bit of the QOS_NLRI attribute in the corresponding
UPDATE message, leaving the one-way delay information detailed in
both QoS Information Code and Sub-code unchanged.
Upon receipt of the UPDATE message sent by router A, router E will
update the one-way delay information since it is a QOS_NRLI-capable
peer. Finally, router D receives the UPDATE message, and selects a
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route with a 40 milliseconds one-way delay to reach network
192.0.20.0, as depicted in figure 3.
[Fig. 3: Selecting QoS Routes Across Domains.]
This simulation result shows that the selection of a delay-inferred
route over a BGP route may not yield an optimal decision. In the
above example, the 40 ms-route goes through routers D-E-A-S, while a
"truly optimal" BGP route would be through routers D-E-F-A-S, hence a
38 ms-route. This is because of a BGP4 rule that does not allow
router F to send an UPDATE message towards router E, because router F
received the UPDATE message from router A thanks to the iBGP
connection it has established with A.
7.3. Additional Results
The following table reflects the results obtained from a simulation
network composed of 9 autonomous systems and 20 BGP peers. The
numbers contained in the columns reflect the percentage of serviced
requirements, where the requirements are expressed in terms of delay.
Three parameters have been taken into account:
- The percentage of BGP peers that have the ability to process the
information conveyed in the QOS_NLRI attribute (denoted as "x% Q-
BGP" in the following table),
- The transit delays "observed" (and artificially simulated) on each
transmission link: the higher the delays, the lower the percentage
of serviced QoS requirements,
- The QoS requirements themselves, expressed in terms of delay: as
such, the strongest requirements (i.e. the lowest delays) have less
chance to be satisfied.
+-------------------------------------------+
| Delay | 0% Q-BGP | 50% Q-BGP | 100% Q-BGP |
+-------------------------------------------+
| 3 | 11 | 8,3 | 11 |
+-------------------------------------------+
| 5 | 30,5 | 30,5 | 36,1 |
+-------------------------------------------+
| 6 | 40 | 47,2 | 55,5 |
+-------------------------------------------+
| 7 | 47 | 59,7 | 72,2 |
+-------------------------------------------+
| 8 | 62,5 | 79 | 91,6 |
+-------------------------------------------+
| 9 | 63 | 84,7 | 97,2 |
+-------------------------------------------+
| 10 | 70,8 | 90,2 | 98,6 |
+-------------------------------------------+
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| 11 | 76,3 | 93 | 98,6 |
+-------------------------------------------+
| 12 | 86,1 | 97,2 | 100 |
+-------------------------------------------+
| 13 | 88,8 | 98,6 | 100 |
+-------------------------------------------+
| 14 | 94,4 | 100 | 100 |
+-------------------------------------------+
| 15 | 94,4 | 100 | 100 |
+-------------------------------------------+
| 16 | 94,4 | 100 | 100 |
+-------------------------------------------+
| 17 | 97,2 | 100 | 100 |
+-------------------------------------------+
| 18 | 98,6 | 100 | 100 |
+-------------------------------------------+
| 19 | 98,6 | 100 | 100 |
+-------------------------------------------+
| 20 | 98,6 | 100 | 100 |
+-------------------------------------------+
| 21 | 98,6 | 100 | 100 |
+-------------------------------------------+
| 22 | 100 | 100 | 100 |
+-------------------------------------------+
This table clearly demonstrates the technical feasibility of the
approach, and how the use of the QOS_NLRI attribute can improve the
percentage of serviced QoS requirements.
7.4. Next Steps
This simulation effort is currently pursued in order to better
qualify the interest of using the BGP4 protocol to convey QoS-related
information between domains, from a scalability perspective, i.e. the
growth of BGP traffic vs. the stability of the network.
The stability of the IP network is probably one of the most important
aspects, since QoS-related information is subject to very dynamic
changes, thus yielding non-negligible risks of flapping.
8. IANA Considerations
Section 4 of this draft documents an optional transitive BGP-4
attribute named "QOS_NLRI" whose type value will be assigned by IANA.
Section 5 of this draft also documents a Capability Code whose value
should be assigned by IANA as well.
9. Security Considerations
This additional BGP-4 attribute specification does not change the
underlying security issues inherent in the existing BGP-4 protocol
specification [14].
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10. References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Rekhter, Y., Li T., "A Border Gateway Protocol 4 (BGP-4)", RFC
1771, March 1995.
[4] Almes, G., Kalidindi, S., "A One-Way-Delay Metric for IPPM", RFC
2679, September 1999.
[5] Demichelis, C., Chimento, P., "IP Packet Delay Variation Metric
for IP Performance Metrics (IPPM)", RFC 3393, November 2002.
[6] Nichols, K., Blake, S., Baker, F., Black, D., "Definition of the
Differentiated Services Field (DS Field) in the IPv4 and IPv6
Headers", RFC 2474, December 1998.
[7] Traina, P., McPherson, D., Scudder, J., "Autonomous System
Confederations for BGP", RFC 3065, February 2001.
[8] Jacquenet, C., "A COPS Client-Type for Traffic Engineering",
draft-jacquenet-cops-te-00.txt, Work in Progress, February 2004.
[9] Apostolopoulos, G. et al, "QoS Routing Mechanisms and OSPF
Extensions", RFC 2676, August 1999.
[10] Reynolds, J., Postel, J., "ASSIGNED NUMBERS", RFC 1700, October
1994.
[11] Walton, D., et al., "Advertisement of Multiple Paths in BGP",
draft-walton-bgp-add-paths-01.txt, Work in Progress, November
2002.
[12] Chandra, R., Scudder, J., "Capabilities Advertisement with BGP-
4", RFC 3392, November 2002.
[13] Narten, T., Alvestrand, H., "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 2434, October 1998.
[14] Heffernan, A., "Protection of BGP sessions via the TCP MD5
Signature Option", RFC 2385, August 1998.
11. Acknowledgments
Part of this work is funded by the European Commission, within the
context of the MESCAL (Management of End-to-End Quality of Service
Across the Internet At Large, http://www.mescal.org) project, which
is itself part of the IST (Information Society Technologies) research
program.
The author would also like to thank all the partners of the MESCAL
project for the fruitful discussions that have been conducted within
the context of the traffic engineering specification effort of the
project, as well as O. Bonaventure and B. Carpenter for their
valuable input.
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12. Authors' Addresses
Geoffrey Cristallo
Alcatel
Francis Wellesplein, 1
2018 Antwerp
Belgium
Phone: +32 (0)3 240 7890
E-Mail: geoffrey.cristallo@alcatel.be
Christian Jacquenet
France Telecom
3, avenue Fran‡ois Ch‚teau
CS 36901
35069 Rennes Cedex
France
Phone: +33 2 99 87 63 31
Email: christian.jacquenet@francetelecom.com
13. Full Copyright Statement
Copyright(C) The Internet Society (2004). All Rights Reserved.
This document and translations of it may be copied and furnished to
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or assist its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
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The limited permissions granted above are perpetual and will not be
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This document and the information contained herein is provided on an
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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