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.

この文書は、インターネットコミュニティのためのインターネット標準トラックプロトコルを指定し、改善のための議論と提案を要求します。このプロトコルの標準化状態と状態への「インターネット公式プロトコル標準」(STD 1)の最新版を参照してください。このメモの配布は無制限です。

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Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved.

著作権(C)2009 IETF信託とドキュメントの作成者として特定の人物。全著作権所有。

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 ( Please review these documents carefully, as they describe your rights and restrictions with respect to this document.

この文書では、BCP 78と、この文書(の発行日に有効なIETFドキュメントに関連IETFトラストの法律の規定に従うものとします。彼らは、この文書に関してあなたの権利と制限を説明するように、慎重にこれらの文書を確認してください。

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.




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.

この文書はRFC 3392を廃止します。

1. Introduction
1. はじめに

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].

この文書のキーワード "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", および "OPTIONAL" はRFC 2119 [RFC2119]に記載されているように解釈されます。

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.

BGPスピーカは機能オプションのパラメータを運ぶOPENメッセージに応答して、スピーカーがサポートされていないオプションのパラメータに設定エラーサブコードを持つ通知メッセージを受信した場合など、そのピアが能力の広告をサポートしていないと判断しました。 (これはベースBGP-4仕様[RFC4271]としない新しい要件の結果である。)この場合、スピーカは、ピアに機能オプションパラメータを送信せずピアと再確立BGP接続を試みます。

If a BGP speaker that supports a certain capability determines that its peer doesn't support this capability, the speaker MAY send a NOTIFICATION message to the peer and terminate peering (see Section "Extensions to Error Handling" for more details). For example, a BGP speaker may need to terminate peering if it established peering to exchange IPv6 routes and determines that its peer does not support Multiprotocol Extensions for BGP-4 [RFC4760]. The Error Subcode in the NOTIFICATION message is then set to Unsupported Capability. The message MUST contain the capability or capabilities that cause the speaker to send the message. The decision to send the message and terminate the peering is local to the speaker. If terminated, such peering SHOULD NOT be re-established automatically.

特定の機能をサポートしているBGPスピーカは、そのピアがこの機能をサポートしていないと判断された場合、スピーカーがピアに通知メッセージを送信し、(詳細は、「エラー処理拡張機能」のセクションを参照してください)ピアリング終了することができます。それはIPv6ルートを交換するピアリング確立し、そのピアがBGP-4 [RFC4760]のためのマルチプロトコル拡張をサポートしていないと判定した場合、例えば、BGPスピーカは、ピアリング終了する必要があるかもしれません。通知メッセージにエラーサブコードは、その後、サポートされていない機能に設定されています。メッセージは、メッセージを送信するためにスピーカーを引き起こす能力や機能を含まなければなりません。メッセージを送信し、ピアリングを終了するという決定は、スピーカーにローカルです。終了した場合は、そのようなピアリングは自動的に再確立されるべきではありません。

If a BGP speaker receives from its peer a capability that it does not itself support or recognize, it MUST ignore that capability. In particular, the Unsupported Capability NOTIFICATION message MUST NOT be generated and the BGP session MUST NOT be terminated in response to reception of a capability that is not supported by the local speaker.


4. Capabilities Optional Parameter (Parameter Type 2):

This is an Optional Parameter that is used by a BGP speaker to convey to its BGP peer the list of capabilities supported by the speaker. The encoding of BGP Optional Parameters is specified in Section 4.2 of [RFC4271]. The parameter type of the Capabilities Optional Parameter is 2.

これは、BGPスピーカーによってサポートされる機能のリストをピアに伝えるためにBGPスピーカーによって使用されるオプションのパラメータです。 BGPオプションパラメータの符号化は[RFC4271]のセクション4.2で指定されています。能力任意パラメータのパラメータタイプは2です。

The parameter contains one or more triples <Capability Code, Capability Length, Capability Value>, where each triple is encoded as shown below:


          | Capability Code (1 octet)    |
          | Capability Length (1 octet)  |
          | Capability Value (variable)  |
          ~                              ~

The use and meaning of these fields are as follows:


Capability Code:


Capability Code is a one-octet unsigned binary integer that unambiguously identifies individual capabilities.


Capability Length:


Capability Length is a one-octet unsigned binary integer that contains the length of the Capability Value field in octets.


Capability Value:


Capability Value is a variable-length field that is interpreted according to the value of the Capability Code field.


BGP speakers SHOULD NOT include more than one instance of a capability with the same Capability Code, Capability Length, and Capability Value. Note, however, that processing of multiple instances of such capability does not require special handling, as additional instances do not change the meaning of the announced capability; thus, a BGP speaker MUST be prepared to accept such multiple instances.


BGP speakers MAY include more than one instance of a capability (as identified by the Capability Code) with non-zero Capability Length field, but with different Capability Value and either the same or different Capability Length. Processing of these capability instances is specific to the Capability Code and MUST be described in the document introducing the new capability.


The Capabilities Optional Parameter (OPEN Optional Parameter Type 2) SHOULD only be included in the OPEN message once. If the BGP speaker wishes to include multiple capabilities in the OPEN message, it SHOULD do so as discussed above -- by listing all those capabilities as TLVs within a single Capabilities Optional Parameter. However, for backward compatibility, a BGP speaker MUST be prepared to receive an OPEN message that contains multiple Capabilities Optional Parameters, each of which contains one or more capabilities TLVs. The set of capabilities should be processed in the same way in either case, whether it is enumerated within a single Capabilities Optional Parameter of the OPEN message or split across multiple Capabilities Optional Parameters.

能力任意パラメータ(OPENオプションパラメータタイプ2)は、一度だけOPENメッセージに含まれるべきです。 BGPスピーカーがOPENメッセージ内に複数の機能を含めることを望む場合、上述のように、それはそうすべきである - 単一能力任意パラメータ内のTLVとして、これらすべての機能を一覧表示すること。ただし、下位互換性を維持するために、BGPスピーカは、一の以上の機能のTLVを含んで、それぞれが複数の機能オプションのパラメータが含まれているOPENメッセージを受信するように準備しなければなりません。それは、単一の能力の範囲内にOPENメッセージのオプションのパラメータを列挙または複数の機能オプションパラメータにまたがって分割されているかどうか機能のセットは、いずれの場合も同じ方法で処理されなければなりません。

5. Extensions to Error Handling

This document defines a new Error Subcode, Unsupported Capability. The value of this Subcode is 7. The Data field in the NOTIFICATION message MUST list the set of capabilities that causes the speaker to send the message. Each such capability is encoded in the same way as it would be encoded in the OPEN message.


As explained in the "Overview of Operations" section, the Unsupported Capability NOTIFICATION is a way for a BGP speaker to complain that its peer does not support a required capability without which the peering cannot proceed. It MUST NOT be used when a BGP speaker receives a capability that it does not understand; such capabilities MUST be ignored.

セクション「事業の概要」で説明したように、サポートされていない能力通知は、BGPスピーカは、そのピアがピアリングを進めることができないことなく、必要な機能をサポートしていないことを訴えるための方法です。 BGPスピーカーが、それは理解していない機能を受信したときにそれを使用してはいけません。そのような能力を無視しなければなりません。

6. IANA Considerations
6. IANAの考慮事項

This document defines a Capability Optional Parameter along with a Capability Code field. IANA maintains the registry for Capability Code values. Capability Code value 0 is reserved. Capability Code values 1 through 63 are to be assigned by IANA using the "IETF Review" policy defined in [RFC5226]. Capability Code values 64 through 127 are to be assigned by IANA using the "First Come First Served" policy defined in [RFC5226]. Capability Code values 128 through 255 are for "Private Use" as defined in [RFC5226].

この文書では、能力コードフィールドとともに能力任意パラメータを定義します。 IANAは能力コード値のレジストリを維持します。能力コード値0は予約されています。機能コード63を介して1は[RFC5226]で定義された「IETFレビュー」ポリシーを使用して、IANAによって割り当てられる値。機能コード127を介して、64 [RFC5226]で定義された「まず最初に配信是非」ポリシーを使用してIANAによって割り当てられる値。能力コードは、128〜255の値[RFC5226]で定義されるように「私用」のためのものです。

IANA created and maintains a registry for OPEN message Optional Parameters called "BGP OPEN Optional Parameter Types". Optional Parameters are identified by the Parameter Type, which is a one-octet unsigned integer. Values (0 reserved, 1-255) are to be allocated according to the "IETF Review" policy as defined in [RFC5226].

IANAが作成され、「BGP OPENオプションのパラメータ型」と呼ばれるOPENメッセージオプションパラメータのレジストリを維持します。オプションのパラメータは、1オクテットの符号なし整数であるパラメータ・タイプによって識別されます。値(予約0、1-255)は[RFC5226]で定義されるように「IETFレビュー」ポリシーに従って割り当てられることになっています。

The registry has been populated with the two Parameter Type codes that are currently defined:


o Parameter Type 1: Authentication (deprecated) [RFC4271] [RFC5492]


o Parameter Type 2: Capabilities [RFC5492]


7. Security Considerations

This extension to BGP does not change the underlying security issues inherent in the existing BGP [RFC4272].

BGPへのこの拡張は、既存のBGP [RFC4272]に固有の基本的なセキュリティ問題を変更しません。

8. Acknowledgments

The authors would like to thank members of the IDR Working Group and the IESG and its Directorates for their review and comments.


9. References
9.1. Normative References
9.1. 引用規格

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2119]ブラドナーの、S.、 "要件レベルを示すためにRFCsにおける使用のためのキーワード"、BCP 14、RFC 2119、1997年3月。

[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.

[RFC4271] Rekhter、Y.、李、T.、およびS.野兎、 "ボーダーゲートウェイプロトコル4(BGP-4)"、RFC 4271、2006年1月。

[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.

[RFC5226] Narten氏、T.とH. Alvestrand、 "RFCsにIANA問題部に書くためのガイドライン"、BCP 26、RFC 5226、2008年5月。

9.2. Informative References
9.2. 参考文献

[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", RFC 4272, January 2006.

[RFC4272]マーフィー、S.、 "BGPセキュリティの脆弱性分析"、RFC 4272、2006年1月。

[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007.

[RFC4760]ベイツ、T.、チャンドラ、R.、カッツ、D.、およびY. Rekhter、 "BGP-4のためのマルチプロトコル拡張機能"、RFC 4760、2007年1月。

Appendix A. Comparison between and


In addition to several minor editorial changes, RFC 3392 also clarified how to handle multiple instances of the same capability.

いくつかのマイナーな編集上の変更に加えて、RFC 3392にも同じ機能の複数のインスタンスをどのように処理するかを明らかにしました。

Appendix B. Comparison between and This Document


This document makes minor editorial changes and updated references, clarifies the use of the Unsupported Optional Parameter NOTIFICATION message, clarifies behavior when the Capabilities Parameter is included in the OPEN message multiple times, and clarifies requirements by changing a number of SHOULDs to MUSTs.


Authors' Addresses


John G. Scudder Juniper Networks




Ravi Chandra Sonoa Systems