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IETF RFC 5668

4-Octet AS Specific BGP Extended Community

Last modified on Wednesday, October 28th, 2009

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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
   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 may




Rekhter, et al.             Standards Track                  PAGE 1 top


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 [RFC 4360]: 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 [RFC 2119]. 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 top

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 [RFC 4893], 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 [RFC 5226]. 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 0x0203 Rekhter, et al. Standards Track PAGE 3 top

RFC 5668 4-Octet AS Specific Extended Community October 2009 5. 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 [RFC 4593] 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. References 7.1. Normative References [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC 5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. [RFC 4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, February 2006. [RFC 4893] 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. [RFC 4593] 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 top

RFC 5668 4-Octet AS Specific Extended Community October 2009 Authors' 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.com Rekhter, et al. Standards Track PAGE 5 top

4-Octet AS Specific BGP Extended Community RFC TOTAL SIZE: 9017 bytes PUBLICATION DATE: Wednesday, October 28th, 2009 LEGAL RIGHTS: The IETF Trust (see BCP 78)


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