Autonomous System Migration Mechanisms and Their Effects on the BGP AS_PATH Attribute
RFC 7705

Document Type RFC - Proposed Standard (November 2015; No errata)
Updates RFC 4271
Last updated 2015-11-30
Replaces draft-ga-idr-as-migration
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Susan Hares
Shepherd write-up Show (last changed 2015-08-06)
IESG IESG state RFC 7705 (Proposed Standard)
Consensus Boilerplate Yes
Telechat date
Responsible AD Alvaro Retana
Send notices to aretana@cisco.com
IANA IANA review state IANA OK - No Actions Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                         W. George
Request for Comments: 7705                             Time Warner Cable
Updates: 4271                                                  S. Amante
Category: Standards Track                                    Apple, Inc.
ISSN: 2070-1721                                            November 2015

                 Autonomous System Migration Mechanisms
             and Their Effects on the BGP AS_PATH Attribute

Abstract

   This document discusses some existing commonly used BGP mechanisms
   for Autonomous System Number (ASN) migration that are not formally
   part of the BGP4 protocol specification.  It is necessary to document
   these de facto standards to ensure that they are properly supported
   in future BGP protocol work.

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/rfc7705.

Copyright Notice

   Copyright (c) 2015 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.

George & Amante              Standards Track                    [Page 1]
RFC 7705                  AS Migration Features            November 2015

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Documentation Note  . . . . . . . . . . . . . . . . . . .   3
   2.  ASN Migration Scenario Overview . . . . . . . . . . . . . . .   3
   3.  External BGP Autonomous System Migration Mechanisms . . . . .   5
     3.1.  Modify Inbound BGP AS_PATH Attribute  . . . . . . . . . .   5
     3.2.  Modify Outbound BGP AS_PATH Attribute . . . . . . . . . .   7
     3.3.  Implementation  . . . . . . . . . . . . . . . . . . . . .   8
   4.  Internal BGP Autonomous System Migration Mechanisms . . . . .   9
     4.1.  Internal BGP AS Migration . . . . . . . . . . . . . . . .  10
     4.2.  Implementation  . . . . . . . . . . . . . . . . . . . . .  12
   5.  Additional Operational Considerations . . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Appendix A.  Implementation Report  . . . . . . . . . . . . . . .  16
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   This document discusses some existing commonly used BGP mechanisms
   for Autonomous System Number (ASN) migration that are not formally
   part of the BGP4 [RFC4271] protocol specification.  These mechanisms
   are local to a given BGP speaker and do not require negotiation with
   or cooperation of BGP neighbors.  The deployment of these mechanisms
   do not need to interwork with one another to accomplish the desired
   results, so slight variations between existing vendor implementations
   exist and will not necessarily be harmonized due to this document.
   However, it is necessary to document these de facto standards to
   ensure that new implementations can be successful, and any future
   protocol enhancements to BGP that propose to read, copy, manipulate,
   or compare the AS_PATH attribute can do so without inhibiting the use
   of these very widely used ASN migration mechanisms.

   The migration mechanisms discussed here are useful to ISPs and
   organizations of all sizes, but it is important to understand the
   business need for these mechanisms and illustrate why they are so
   critical for ISPs' operations.  During a merger, acquisition, or
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