4-Octet AS Specific BGP Extended Community
RFC 5668

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Network Working Group                                         Y. Rekhter
Request for Comments: 5668                              Juniper Networks
Category: Standards Track                                      S. Sangli
                                                           Cisco Systems
                                                               D. Tappan
                                                              Consultant
                                                            October 2009

               4-Octet AS Specific BGP Extended Community

Abstract

   This document defines a new type of a BGP extended community, which
   carries a 4-octet Autonomous System (AS) number.

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 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
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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   described in the BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may

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RFC 5668         4-Octet AS Specific Extended Community     October 2009

   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

1.  Introduction

   This document defines a new type of BGP extended community [RFC4360]:
   a 4-octet AS specific extended community.  This type of extended
   community is similar to the 2-octet AS specific extended community,
   except that it can carry a 4-octet Autonomous System number.

1.1.  Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  4-Octet AS Specific Extended Community

   This is an extended type with a Type field comprising 2 octets and a
   Value field comprising 6 octets.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 0x02 or 0x42  |   Sub-Type    |    Global Administrator       :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   : Global Administrator (cont.)  |    Local Administrator        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The value of the high-order octet of this extended type is either
   0x02 (for transitive communities) or 0x42 (for non-transitive
   communities).  The low-order octet of this extended type is used to
   indicate sub-types.

   The Value field consists of 2 sub-fields:

      Global Administrator sub-field: 4 octets

         This sub-field contains a 4-octet Autonomous System number
         assigned by IANA.

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RFC 5668         4-Octet AS Specific Extended Community     October 2009

      Local Administrator sub-field: 2 octets

         The organization identified by the Autonomous System number in
         the Global Administrator sub-field can encode any information
         in this sub-field.  The format and meaning of the value encoded
         in this sub-field should be defined by the sub-type of the
         community.

3.  Considerations for 2-Octet Autonomous Systems

   As per [RFC4893], a 2-octet Autonomous System number can be converted
   into a 4-octet Autonomous System number by setting the 2 high-order
   octets of the 4-octet field to zero.

   As a consequence, at least in principle, an Autonomous System that