RFC6286

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.

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.

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.

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.

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".

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.

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).

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.

Security Considerations

This extension to BGP does not introduce new security considerations. BGP security considerations are discussed in RFC4271.

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., 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]