Capabilities Advertisement with BGP-4
RFC 5492
Document | Type |
RFC - Draft Standard
(February 2009; No errata)
Updated by RFC 8810
Obsoletes RFC 3392
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Authors | Ravi Chandra , John Scudder | ||
Last updated | 2020-07-29 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 5492 (Draft Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | David Ward | ||
Send notices to | (None) |
Network Working Group J. Scudder Request for Comments: 5492 Juniper Networks Obsoletes: 3392 R. Chandra Category: Standards Track Sonoa Systems February 2009 Capabilities Advertisement with BGP-4 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. 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 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. Abstract This document defines an Optional Parameter, called Capabilities, that is expected to facilitate the introduction of new capabilities in the Border Gateway Protocol (BGP) by providing graceful capability advertisement without requiring that BGP peering be terminated. This document obsoletes RFC 3392. Scudder & Chandra Standards Track [Page 1] RFC 5492 Capabilities Advertisement February 2009 1. Introduction The base BGP-4 specification [RFC4271] requires that when a BGP speaker receives an OPEN message with one or more unrecognized Optional Parameters, the speaker must terminate the BGP peering. This complicates the introduction of new capabilities in BGP. This specification defines an Optional Parameter and processing rules that allow BGP speakers to communicate capabilities in an OPEN message. A pair of BGP speakers that supports this specification can establish the peering even when presented with unrecognized capabilities, so long as all capabilities required to support the peering are supported. 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 RFC 2119 [RFC2119]. 3. Overview of Operations When a BGP speaker [RFC4271] that supports capabilities advertisement sends an OPEN message to its BGP peer, the message MAY include an Optional Parameter, called Capabilities. The parameter lists the capabilities supported by the speaker. A BGP speaker determines the capabilities supported by its peer by examining the list of capabilities present in the Capabilities Optional Parameter carried by the OPEN message that the speaker receives from the peer. A BGP speaker that supports a particular capability may use this capability with its peer after the speaker determines (as described above) that the peer supports this capability. Simply put, a given capability can be used on a peering if that capability has been advertised by both peers. If either peer has not advertised it, the capability cannot be used. A BGP speaker determines that its peer doesn't support capabilities advertisement if, in response to an OPEN message that carries the Capabilities Optional Parameter, the speaker receives a NOTIFICATION message with the Error Subcode set to Unsupported Optional Parameter. (This is a consequence of the base BGP-4 specification [RFC4271] and not a new requirement.) In this case, the speaker SHOULD attempt to re-establish a BGP connection with the peer without sending to the peer the Capabilities Optional Parameter. Scudder & Chandra Standards Track [Page 2] RFC 5492 Capabilities Advertisement February 2009 If a BGP speaker that supports a certain capability determines thatShow full document text