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.




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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".










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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).






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  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: [email protected]

  Jenny Yuan
  Cisco Systems, Inc.
  170 W. Tasman Dr.
  San Jose, CA 95134

  EMail: [email protected]













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