BGP Extended Communities Attribute
RFC 4360
Document | Type | RFC - Proposed Standard (February 2006; Errata) | |
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Authors | Dan Tappan , Srihari Sangli , Yakov Rekhter | ||
Last updated | 2020-01-21 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4360 (Proposed Standard) | |
Action Holders |
(None)
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||
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Bill Fenner | ||
Send notices to | (None) |
Network Working Group S. Sangli Request for Comments: 4360 D. Tappan Category: Standards Track Cisco Systems Y. Rekhter Juniper Networks February 2006 BGP Extended Communities Attribute 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) The Internet Society (2006). Abstract This document describes the "extended community" BGP-4 attribute. This attribute provides a mechanism for labeling information carried in BGP-4. These labels can be used to control the distribution of this information, or for other applications. 1. Introduction The Extended Community Attribute provides a mechanism for labeling information carried in BGP-4 [BGP-4]. It provides two important enhancements over the existing BGP Community Attribute [RFC1997]: - An extended range, ensuring that communities can be assigned for a plethora of uses, without fear of overlap. - The addition of a Type field provides structure for the community space. The addition of structure allows the usage of policy based on the application for which the community value will be used. For example, one can filter out all communities of a particular type, or allow only certain values for a particular type of community. It also allows one to specify whether a particular community is transitive or non-transitive across an Autonomous System (AS) boundary. Without structure, this can only be accomplished by explicitly enumerating Sangli, et al. Standards Track [Page 1] RFC 4360 BGP Extended Communities Attribute February 2006 all community values that will be denied or allowed and passed to BGP speakers in neighboring ASes based on the transitive property. 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. BGP Extended Communities Attribute The Extended Communities Attribute is a transitive optional BGP attribute, with the Type Code 16. The attribute consists of a set of "extended communities". All routes with the Extended Communities attribute belong to the communities listed in the attribute. Each Extended Community is encoded as an 8-octet quantity, as follows: - Type Field : 1 or 2 octets - Value Field : Remaining 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type high | Type low(*) | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Value | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ (*) Present for Extended types only, used for the Value field otherwise. Type Field: Two classes of Type Field are introduced: Regular type and Extended type. The size of Type Field for Regular types is 1 octet, and the size of the Type Field for Extended types is 2 octets. The value of the high-order octet of the Type Field determines if an extended community is a Regular type or an Extended type. The class of a type (Regular or Extended) is not encoded in the structure of the type itself. The class of a type is specified in the document that defines the type and the IANA registry. Sangli, et al. Standards Track [Page 2] RFC 4360 BGP Extended Communities Attribute February 2006 The high-order octet of the Type Field is as shown below: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |I|T| | +-+-+-+-+-+-+-+-+ I - IANA authority bit Value 0: IANA-assignable type using the "First Come First Serve" policy Value 1: Part of this Type Field space is for IANA assignable types using either the Standard Action or the Early IANA Allocation policy. The rest of this TypeShow full document text