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Internet Engineering Task Force (IETF)                     J. Heitz, Ed.Request for Comments: 8092                                         CiscoCategory: Standards Track                               J. Snijders, Ed.ISSN: 2070-1721                                                      NTT                                                                K. Patel                                                                  Arrcus                                                             I. Bagdonas                                                                 Equinix                                                             N. Hilliard                                                                    INEX                                                           February 2017BGP Large Communities AttributeAbstract   This document describes the BGP Large Communities attribute, an   extension to BGP-4.  This attribute provides a mechanism to signal   opaque information within separate namespaces to aid in routing   management.  The attribute is suitable for use with all Autonomous   System Numbers (ASNs) including four-octet ASNs.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 inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc8092.Heitz, et al.                Standards Track                    [Page 1]

RFC 8092                  BGP Large Communities            February 2017Copyright Notice   Copyright (c) 2017 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 Simplified BSD License.Table of Contents1. Introduction ....................................................22. Requirements Language ...........................................33. BGP Large Communities Attribute .................................34. Aggregation .....................................................45. Canonical Representation ........................................46. Error Handling ..................................................57. Security Considerations .........................................58. IANA Considerations .............................................69. References ......................................................69.1. Normative References .......................................69.2. Informative References .....................................6   Acknowledgments ....................................................7   Contributors .......................................................7   Authors' Addresses .................................................81.  Introduction   BGP [RFC4271] implementations typically support a routing policy   language to control the distribution of routing information.  Network   operators attach BGP communities to routes to associate particular   properties with these routes.  These properties may include   information such as the route origin location, or specification of a   routing policy action to be taken, or one that has been taken, and is   applied to all routes contained in a BGP Update Message where the   Communities Attribute is included.  Because BGP communities are   optional transitive BGP attributes, BGP communities may be acted upon   or otherwise used by routing policies in other Autonomous Systems   (ASes) on the Internet.Heitz, et al.                Standards Track                    [Page 2]

RFC 8092                  BGP Large Communities            February 2017   A BGP Communities attribute is a variable-length attribute consisting   of a set of one or more four-octet values, each of which specify a   community [RFC1997].  Common use of the individual values of this   attribute type split this single 32-bit value into two 16-bit values.   The most significant word is interpreted as an Autonomous System   Number (ASN), and the least significant word is a locally defined   value whose meaning is assigned by the operator of the AS in the most   significant word.   Since the adoption of four-octet ASNs [RFC6793], the BGP Communities   attribute can no longer accommodate the above encoding, as a two-   octet word cannot fit a four-octet ASN.  The BGP Extended Communities   attribute [RFC4360] is also unsuitable.  The six-octet length of the   Extended Community value precludes the common operational practice of   encoding four-octet ASNs in both the Global Administrator and the   Local Administrator sub-fields.   To address these shortcomings, this document defines a BGP Large   Communities attribute encoded as an unordered set of one or more   twelve-octet values, each consisting of a four-octet Global   Administrator field and two four-octet operator-defined fields, each   of which can be used to denote properties or actions significant to   the operator of the AS assigning the values.2.  Requirements Language   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 [RFC2119].3.  BGP Large Communities Attribute   This document defines the BGP Large Communities attribute as an   optional transitive path attribute of variable length.  All routes   with the BGP Large Communities attribute belong to the communities   specified in the attribute.Heitz, et al.                Standards Track                    [Page 3]

RFC 8092                  BGP Large Communities            February 2017   Each BGP Large Community value is encoded as a 12-octet quantity, as   follows:    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                      Global Administrator                     |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                       Local Data Part 1                       |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                       Local Data Part 2                       |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Global Administrator:  A four-octet namespace identifier.   Local Data Part 1:  A four-octet operator-defined value.   Local Data Part 2:  A four-octet operator-defined value.   The Global Administrator field is intended to allow different ASes to   define BGP Large Communities without collision.  This field SHOULD be   an ASN, in which case the Local Data Parts are to be interpreted as   defined by the owner of the ASN.  The use of Reserved ASNs (0   [RFC7607], 65535 and 4294967295 [RFC7300]) is NOT RECOMMENDED.   There is no significance to the order in which twelve-octet Large   Community Attribute values are encoded in a Large Communities   attribute, A BGP speaker can transmit them in any order.   Duplicate BGP Large Community values MUST NOT be transmitted.  A   receiving speaker MUST silently remove redundant BGP Large Community   values from a BGP Large Community attribute.4.  Aggregation   If a range of routes is aggregated, then the resulting aggregate   should have a BGP Large Communities attribute that contains all of   the BGP Large Communities attributes from all of the aggregated   routes.5.  Canonical Representation   The canonical representation of BGP Large Communities is three   separate unsigned integers in decimal notation in the following   order: Global Administrator, Local Data 1, Local Data 2.  Numbers   MUST NOT contain leading zeros; a zero value MUST be represented with   a single zero.  Each number is separated from the next by a single   colon.  For example: 64496:4294967295:2, 64496:0:0.Heitz, et al.                Standards Track                    [Page 4]

RFC 8092                  BGP Large Communities            February 2017   BGP Large Communities SHOULD be represented in the canonical   representation.6.  Error Handling   The error handling of BGP Large Communities is as follows:   o  A BGP Large Communities attribute SHALL be considered malformed if      the length of the BGP Large Communities Attribute value, expressed      in octets, is not a non-zero multiple of 12.   o  A BGP Large Communities attribute SHALL NOT be considered      malformed due to presence of duplicate Large Community values.   o  A BGP UPDATE message with a malformed BGP Large Communities      attribute SHALL be handled using the approach of "treat-as-      withdraw" as described inSection 2 of [RFC7606].   The BGP Large Communities Global Administrator field may contain any   value, and a BGP Large Communities attribute MUST NOT be considered   malformed if the Global Administrator field contains an unallocated,   unassigned, or reserved ASN.7.  Security Considerations   This document does not change any underlying security issues   associated with any other BGP Communities mechanism.  Specifically,   an AS relying on the BGP Large Communities attribute carried in BGP   must have trust in every other AS in the path, as any intermediate AS   in the path may have added, deleted, or altered the BGP Large   Communities attribute.  Specifying the mechanism to provide such   trust is beyond the scope of this document.   BGP Large Communities do not protect the integrity of each community   value.  Operators should be aware that it is possible for a BGP   speaker to alter BGP Large Community Attribute values in a BGP Update   Message.  Protecting the integrity of the transitive handling of BGP   Large Community attributes in a manner consistent with the intent of   expressed BGP routing policies falls within the broader scope of   securing BGP, and is not specifically addressed here.   Network administrators should note the recommendations inSection 11   of "BGP Operations and Security" [RFC7454].Heitz, et al.                Standards Track                    [Page 5]

RFC 8092                  BGP Large Communities            February 20178.  IANA Considerations   IANA has assigned the value 32 (LARGE_COMMUNITY) in the "BGP Path   Attributes" subregistry under the "Border Gateway Protocol (BGP)   Parameters" registry.9.  References9.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <http://www.rfc-editor.org/info/rfc2119>.   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A              Border Gateway Protocol 4 (BGP-4)",RFC 4271,              DOI 10.17487/RFC4271, January 2006,              <http://www.rfc-editor.org/info/rfc4271>.   [RFC7606]  Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.              Patel, "Revised Error Handling for BGP UPDATE Messages",RFC 7606, DOI 10.17487/RFC7606, August 2015,              <http://www.rfc-editor.org/info/rfc7606>.9.2.  Informative References   [RFC1997]  Chandra, R., Traina, P., and T. Li, "BGP Communities              Attribute",RFC 1997, DOI 10.17487/RFC1997, August 1996,              <http://www.rfc-editor.org/info/rfc1997>.   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended              Communities Attribute",RFC 4360, DOI 10.17487/RFC4360,              February 2006, <http://www.rfc-editor.org/info/rfc4360>.   [RFC6793]  Vohra, Q. and E. Chen, "BGP Support for Four-Octet              Autonomous System (AS) Number Space",RFC 6793,              DOI 10.17487/RFC6793, December 2012,              <http://www.rfc-editor.org/info/rfc6793>.   [RFC7300]  Haas, J. and J. Mitchell, "Reservation of Last Autonomous              System (AS) Numbers",BCP 6,RFC 7300,              DOI 10.17487/RFC7300, July 2014,              <http://www.rfc-editor.org/info/rfc7300>.   [RFC7454]  Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations              and Security",BCP 194,RFC 7454, DOI 10.17487/RFC7454,              February 2015, <http://www.rfc-editor.org/info/rfc7454>.Heitz, et al.                Standards Track                    [Page 6]

RFC 8092                  BGP Large Communities            February 2017   [RFC7607]  Kumari, W., Bush, R., Schiller, H., and K. Patel,              "Codification of AS 0 Processing",RFC 7607,              DOI 10.17487/RFC7607, August 2015,              <http://www.rfc-editor.org/info/rfc7607>.Acknowledgments   The authors would like to thank Ruediger Volk, Russ White, Acee   Lindem, Shyam Sethuram, Jared Mauch, Joel M.  Halpern, Jeffrey Haas,   Gunter van de Velde, Marco Marzetti, Eduardo Ascenco Reis, Mark   Schouten, Paul Hoogsteder, Martijn Schmidt, Greg Hankins, Bertrand   Duvivier, Barry O'Donovan, Grzegorz Janoszka, Linda Dunbar, Marco   Davids, Gaurab Raj Upadhaya, Jeff Tantsura, Teun Vink, Adam   Davenport, Theodore Baschak, Pier Carlo Chiodi, Nabeel Cocker, Ian   Dickinson, Jan Baggen, Duncan Lockwood, David Farmer, Randy Bush, Wim   Henderickx, Stefan Plug, Kay Rechthien, Rob Shakir, Warren Kumari,   Gert Doering, Thomas King, Mikael Abrahamsson, Wesley Steehouwer,   Sander Steffann, Brad Dreisbach, Martin Millnert, Christopher Morrow,   Jay Borkenhagen, Arnold Nipper, Joe Provo, Niels Bakker, Bill Fenner,   Tom Daly, Ben Maddison, Alexander Azimov, Brian Dickson, Peter van   Dijk, Julian Seifert, Tom Petch, Tom Scholl, Arjen Zonneveld, Remco   van Mook, Adam Chappell, Jussi Peltola, Kristian Larsson, Markus   Hauschild, Richard Steenbergen, David Freedman, Richard Hartmann,   Geoff Huston, Mach Chen, and Alvaro Retana for their support,   insightful review, and comments.Contributors   The following people contributed significantly to the content of the   document:   John Heasley   NTT Communications   Email: heas@shrubbery.net   Adam Simpson   Nokia   Email: adam.1.simpson@nokia.comHeitz, et al.                Standards Track                    [Page 7]

RFC 8092                  BGP Large Communities            February 2017Authors' Addresses   Jakob Heitz (editor)   Cisco   170 West Tasman Drive   San Jose, CA  95054   United States of America   Email: jheitz@cisco.com   Job Snijders (editor)   NTT Communications   Theodorus Majofskistraat 100   Amsterdam  1065 SZ   The Netherlands   Email: job@ntt.net   Keyur Patel   Arrcus, Inc.   Email: keyur@arrcus.com   Ignas Bagdonas   Equinix   80 Cheapside   London  EC2V 6EE   United Kingdom   Email: ibagdona.ietf@gmail.com   Nick Hilliard   INEX   4027 Kingswood Road   Dublin  24   Ireland   Email: nick@inex.ieHeitz, et al.                Standards Track                    [Page 8]