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Network Working Group                                         Y. RekhterRequest for Comments: 5668                              Juniper NetworksCategory: Standards Track                                      S. Sangli                                                           Cisco Systems                                                               D. Tappan                                                              Consultant                                                            October 2009               4-Octet AS Specific BGP Extended CommunityAbstract   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 toBCP 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 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 mayRekhter, et al.             Standards Track                     [Page 1]

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 inRFC 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.Rekhter, et al.             Standards Track                     [Page 2]

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   uses a 2-octet Autonomous System number could use either 2-octet or   4-octet AS specific extended communities.  This is undesirable, as   both communities would be treated as different, even if they had the   same Sub-Type and Local Administrator values.   Therefore, for backward compatibility with existing deployments and   to avoid inconsistencies between 2-octet and 4-octet specific   extended communities, Autonomous Systems that use 2-octet Autonomous   System numbers SHOULD use 2-octet AS specific extended communities   rather than 4-octet AS specific extended communities.4.  IANA Considerations   This document defines a class of extended communities, called 4-octet   AS specific extended communities, for which the IANA has created and   will maintain a registry entitled Four-octet AS Specific Extended   Community.  All the communities in this class are of extended Types.   Future assignments are to be made using the "First Come First Served"   policy defined in [RFC5226].  The Type values for the transitive   communities of the 4-octet AS specific extended community class are   0x0200-0x02ff; for the non-transitive communities of that class, they   are 0x4200-0x42ff.  Assignments consist of a name and the value.   This document makes the following assignments for the 4-octet AS   specific extended community:      Name                                     Type Value      ----                                     ----------      four-octet AS specific Route Target       0x0202      four-octet AS specific Route Origin       0x0203Rekhter, et al.             Standards Track                     [Page 3]

RFC 5668         4-Octet AS Specific Extended Community     October 20095.  Security Considerations   This document does not add new security issues.  All the security   considerations for BGP extended communities apply here.  At the time   that this document was written, there were significant efforts   underway to improve the security properties of BGP.  For examples of   documents that have been produced up to this time of publication, see   [RFC4593] and [SIDR].   There is a potential serious issue if a malformed, optional   transitive attribute is received.  This issue and the steps to avoid   it are discussed in [OPT_TRANS].6.  Acknowledgements   Thanks to Bruno Decraene for his contributions to this document.7.  References7.1.  Normative References   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate               Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC5226]   Narten, T. and H. Alvestrand, "Guidelines for Writing an               IANA Considerations Section in RFCs",BCP 26,RFC 5226,               May 2008.   [RFC4360]   Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended               Communities Attribute",RFC 4360, February 2006.   [RFC4893]   Vohra, Q. and E. Chen, "BGP Support for Four-octet AS               Number Space",RFC 4893, May 2007.7.2.  Informative References   [OPT_TRANS] Scudder, J., and E. Chen, "Error Handling for Optional               Transitive BGP Attributes", Work in Progress, April 2009.   [RFC4593]   Barbir, A., Murphy, S., and Y. Yang, "Generic Threats to               Routing Protocols",RFC 4593, October 2006.   [SIDR]      Lepinski, M. and S. Kent, "An Infrastructure to Support               Secure Internet Routing", Work in Progress, July 2009.Rekhter, et al.             Standards Track                     [Page 4]

RFC 5668         4-Octet AS Specific Extended Community     October 2009Authors' Addresses   Yakov Rekhter   Juniper Networks, Inc.   EMail: yakov@juniper.net   Srihari R. Sangli   Cisco Systems, Inc.   EMail: rsrihari@cisco.com   Dan Tappan   Boxborough MA   EMail: Dan.Tappan@Gmail.comRekhter, et al.             Standards Track                     [Page 5]