Network Working Group                                           E. Chen
Internet Draft                                                  J. Yuan
Intended Status: Standards Track                          Cisco Systems
Expiration Date: February 2010                           August 3, 2009


                AS-wide Unique BGP Identifier for BGP-4

                  draft-ietf-idr-bgp-identifier-10.txt


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Abstract

   To accommodate situations where the current requirements for the BGP



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   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 do not introduce any backward compatibility issue.


. 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, 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 issue.


. 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



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     and the message is from an internal peer, then the Error Subcode
     is set to "Bad BGP Identifier".


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 four-octet AS numbers are
   involved [RFC4893].


. 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 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



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       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
   current usage of the BGP Identifier.


. Security Considerations

   This extension to BGP does not change the underlying security issues.


. IANA Considerations

   This document has no actions for IANA.


. 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.


. Normative References

   [RFC4271] Rekhter, Y., T. Li, and S. Hares, "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




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   EMail: jenny@cisco.com


















































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