Internet Engineering Task Force (IETF) E. Chen
Request for Comments: 6286 J. Yuan
Updates: 4271 Cisco Systems
Category: Standards Track June 2011
ISSN: 2070-1721
Autonomous-System-Wide Unique BGP Identifier for BGP-4
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 Autonomous-System-
wide (AS-wide) uniqueness of the BGP Identifiers is required. These
revisions to the base BGP specification do not introduce any backward
compatibility issues. This document updates RFC 4271.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6286.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Chen & Yuan Standards Track [Page 1]RFC 6286 AS-Wide Unique BGP ID for BGP-4 June 2011
1. Introduction
Currently, the BGP Identifier of a BGP speaker is specified as a
valid IPv4 host address assigned to the BGP speaker [RFC4271]. 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 (such as in the case of an IPv6-only network),
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 do not
introduce any backward compatibility issues.
2. Protocol Revisions
The revisions to the base BGP specification [RFC4271] include the
definition of the BGP Identifier and procedures for a BGP speaker
that supports the AS-wide Unique BGP Identifier.
2.1. 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.
2.2. 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".
Chen & Yuan Standards Track [Page 2]RFC 6286 AS-Wide Unique BGP ID for BGP-4 June 2011
2.3. 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 4-octet AS numbers are
involved [RFC4893].
3. Remarks
It is noted that a BGP Identifier allocated based on [RFC4271] 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 cannot
share a BGP Identifier with its external neighbor until the remote
BGP speaker is upgraded with software that supports the specified
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 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).
Chen & Yuan Standards Track [Page 3]RFC 6286 AS-Wide Unique BGP ID for BGP-4 June 2011
Therefore, it is concluded that the revisions specified in this
document do not introduce any backward compatibility issues with the
current usage of the BGP Identifier.
4. Security Considerations
This extension to BGP does not introduce new security considerations.
BGP security considerations are discussed in [RFC4271].
5. Acknowledgments
The authors would like to thank members of the IDR Working Group for
discussions on the "IPv6-only Network" related issues that inspired
this document.
6. Normative References
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border
Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
Number Space", RFC 4893, May 2007.
Authors' Addresses
Enke Chen
Cisco Systems, Inc.
170 W. Tasman Dr.
San Jose, CA 95134
EMail: enkechen@cisco.com
Jenny Yuan
Cisco Systems, Inc.
170 W. Tasman Dr.
San Jose, CA 95134
EMail: jenny@cisco.com
Chen & Yuan Standards Track [Page 4]
