Network Working Group Enke Chen
Internet Draft Jenny Yuan
Expiration Date: July 2002 Redback Networks
AS-wide Unique BGP Identifier for BGP-4
draft-chen-bgp-identifier-01.txt
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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.
2. Abstract
To accommodate situations where the current requirements for the BGP
Identifier are not met, this document relaxes the definition of the
BGP Identifier to be a 4-octet unsigned, non-zero integer, and
relaxes the "uniqueness" requirement so that only AS-wide uniqueness
of the BGP Identifiers is required. These revisions to the base BGP
specification does not introduce any backward compatibility issue.
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3. Introduction
Currently the BGP Identifier of a BGP speaker is specified as a valid
IPv4 host address assigned to the BGP speaker [BGP-4]. In addition,
the deployed BGP code requires that two BGP speakers be of distinct
BGP Identifiers in order to establish a BGP connection.
To accommodate situations where the current requirements for the BGP
Identifier are not met, this document relaxes the definition of the
BGP Identifier to be a 4-octet unsigned, non-zero integer, and
relaxes the "uniqueness" requirement so that only AS-wide uniqueness
of the BGP Identifiers is required. These revisions to the base BGP
specification does not introduce any backward compatibility issue.
4. Protocol Revisions
The revisions to the base BGP specification [BGP-4] include the
definition of the BGP Identifier and procedures for a BGP speaker
that supports the AS-wide Unique BGP Identifier.
4.1. Definition of the BGP Identifier
For a BGP speaker that supports the AS-wide Unique BGP Identifier,
the BGP Identifier is specified as the following:
The BGP Identifier is a 4-octet unsigned, non-zero integer that
should be unique within an AS. The value of the BGP Identifier for
a BGP speaker is determined on startup and is the same for every
local interface and every BGP peer.
4.2. Open Message Error Handling
For a BGP speaker that supports the AS-wide Unique BGP Identifier,
the OPEN message error handling related to the BGP Identifier is
modified as follows:
If the BGP Identifier field of the OPEN message is zero, or if
it is the same as the BGP Identifier of the local BGP speaker
and the message is from an internal peer, then the Error Subcode
is set to "Bad BGP Identifier".
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4.3. Connection Collision Resolution
For a BGP speaker that supports the AS-wide Unique BGP Identifier,
the procedures for connection collision resolution are extended as
follows to deal with the case in which the two BGP speakers share the
same BGP Identifier (thus it is only applicable to an external peer):
If the BGP Identifiers of the peers involved in the connection
collision are identical, then the connection initiated by the BGP
speaker with the larger AS number is preserved.
This extension covers cases in which the four-octet AS numbers are
involved [BGP-4BYTE-AS].
5. Remarks
It is noted that a BGP Identifier allocated based on [BGP-4] fits the
revised definition.
In case of BGP Confederation, the whole confederation is considered
as one AS for the purpose of supporting the AS-wide Unique BGP
Identifier.
A BGP speaker that supports the AS-wide Unique BGP Identifier can not
share a BGP Identifier with its external neighbor until the remote
BGP speaker is upgraded with software that supports the proposed
revisions.
In addition to the OPEN message, the BGP Identifier is currently also
used in the following areas:
o In the AGGREAGTOR attribute of a route where the combination of
a BGP Identifier and an AS number uniquely identifies the BGP
speaker that performs the route aggregation.
o In the Route Reflection (in lieu of the Cluster-id) within an
AS, where only the BGP Identifier of an internal neighbor may
be propagated in the route reflection related attributes.
o In the route selection, where the BGP Identifier is not used
in comparing a route from an internal neighbor and a route from
an external neighbor. In addition, routes from BGP speakers with
identical BGP Identifiers have been dealt with (e.g., parallel
BGP sessions between two BGP speakers).
Therefore it is concluded that the revisions proposed in this
document do not introduce any backward compatibility issue with the
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current usage of the BGP Identifier.
6. Security Considerations
This extension to BGP does not change the underlying security issues.
7. Acknowledgments
[TBD]
8. References
[BGP-4] Y. Rekhter, and T. Li, "A Border Gateway Protocol 4 (BGP-4)",
draft-ietf-idr-bgp4-16.txt, November 2001.
[BGP-4BYTE-AS] Q. Vohra, E. Chen, "BGP support for four-octet AS
number space", Work in Progress, <draft-ietf-idr-as4bytes-04.txt>,
September 2001.
9. Author Information
Enke Chen
Redback Networks, Inc.
350 Holger Way
San Jose, CA 95134
e-mail: enke@redback.com
Jenny Yuan
Redback Networks, Inc.
350 Holger Way
San Jose, CA 95134
e-mail: jenny@redback.com
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