Network Working Group K. Suzuki Internet-Draft M. Jibiki Intended status: Informational NEC Expires: August 5, 2010 February 2010 Explicit AS_PATH Attribute for BGP Update draft-suzuki-bgp-exp-aspath-00.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 5, 2010. Copyright Notice Copyright (C) 2010 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. Suzuki & Jibiki Expires August 5, 2010 [Page 1] Internet-Draft Explicit AS_PATH Attribute for BGP Update February 2010 Abstract This document describes a extension of BGP for controlling the area where UPDATE messages are propagated. For this purpose, this document defines a new path attribute, explicit AS_PATH Attribute. 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 [1]. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Explicit AS_PATH Attribute . . . . . . . . . . . . . . . . . . 3 2.1. Attribute Format . . . . . . . . . . . . . . . . . . . . . 3 2.2. Handling Processes . . . . . . . . . . . . . . . . . . . . 4 2.2.1. Originating UPDATE message with Explicit AS_PATH . . . 4 2.2.2. Receiving UPDATE message with Explicit AS_PATH . . . . 4 2.2.3. Sending UPDATE message with Explicit AS_PATH . . . . . 4 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6.1. Normative References . . . . . . . . . . . . . . . . . . . 5 6.2. Informative References . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . . . 6 Suzuki & Jibiki Expires August 5, 2010 [Page 2] Internet-Draft Explicit AS_PATH Attribute for BGP Update February 2010 1. Introduction This document describes a extension of BGP for controlling the area where UPDATE messages are propagated. For this purpose, this document defines a new path attribute, explicit AS_PATH Attribute. An UPDATE message with explicit AS_PATH attribute passes over the path specified the attribute. By including this attribute in UPDATE message, the originating BGP speaker can restrict the area where UPDATE messages are propagated. 2. Explicit AS_PATH Attribute The Explicit AS_PATH Attribute is a transitive optional BGP attribute. The type code of this attribute is assigned by IANA. 2.1. Attribute Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Previous-hop AS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Exp path Length| | +-+-+-+-+-+-+-+-+ + ~ Explicit ASes ~ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+ Figure 1: Explicit AS_PATH Attribute Format o Previous-hop AS : The previous-hop AS is a 4-octet length field, containing the 4-octet AS number[3] of the previous hop. o Explicit path Length : The explicit path length is a 1-octet length field, containing the number of ASes (not the number of octets) in the explicit ASes field. o Explicit ASes : The explicit ASes field contains one or more 4-octet AS numbers[3], each encoded as a 4-octet length field. Suzuki & Jibiki Expires August 5, 2010 [Page 3] Internet-Draft Explicit AS_PATH Attribute for BGP Update February 2010 2.2. Handling Processes 2.2.1. Originating UPDATE message with Explicit AS_PATH When a BGP speaker originates an UPDATE message then, the originating speaker MAY append an explicit AS_PATH Attribute to UPDATE message. This explicit AS_PATH Attribute contains its own AS number in the previous-hop AS field, sequence of explicit AS numbers in the explicit ASes field and the number of explicit ASes in the explicit path length filed. 2.2.2. Receiving UPDATE message with Explicit AS_PATH When a BGP speaker receives an UPDATE message from an external peer, the receiving speaker handles the UPDATE message as follows: a. if the value of Previous-hop AS is not same as the AS number of the external peer, the receiving speaker MUST discard the UPDATE message. b. if the value of the first entry in Explicit ASes is not same as the AS number of the receiving speaker, the receiving speaker MUST discard the UPDATE message. c. if the UPDATE message has not been discarded by the above conditions, the receiving speaker MUST remove the first entry from Explicit ASes and MUST update the value of Explicit path Length. The receiving speaker MUST apply a route advertised by the UPDATE message to the BGP decision process (see section 9.1 in [2]). When a BGP speaker receives an UPDATE message from an internal peer, the receiving speaker MUST apply a route advertised by the UPDATE message to the BGP decision process [2]. 2.2.3. Sending UPDATE message with Explicit AS_PATH When a BGP speaker attempts to send an UPDATE message to an external peer, the sending speaker handles the UPDATE message as follows: a. if the value of the first entry in Explicit ASes is not same as the AS number of the external peer, the speaker MUST NOT send the UPDATE message to the external peer. b. if the value of the first entry in Explicit ASes is same as the AS number of the external peer, the speaker MAY send the UPDATE message to the external peer. Suzuki & Jibiki Expires August 5, 2010 [Page 4] Internet-Draft Explicit AS_PATH Attribute for BGP Update February 2010 If a peer to which a BGP speaker attempts to send an UPDATE message is an internal peer, the speaker MUST send the UPDATE message to the internal peer. 3. IANA Considerations This document introduces a new path attribute of BGP. The type code of this attribute has to be assigned from the registry of BGP Path Attributes maintained by IANA. 4. Security Considerations RFC4271 [2] discusses security considerations concerning BGP. This document describes only a extension for BGP, and so those considerations apply to this extension, too. There are no known additional security concerns for this extension. 5. Acknowledgments The work was partly supported by the Ministry of Internal Affairs and Communications, Japan. 6. References 6.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 6.2. Informative References [2] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [3] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS Number Space", RFC 4893, May 2007. Suzuki & Jibiki Expires August 5, 2010 [Page 5] Internet-Draft Explicit AS_PATH Attribute for BGP Update February 2010 Authors' Addresses Kazuya Suzuki NEC Corporation 1753, Shimonumabe, Nakahara-ku Kawasaki, Kanagawa 211-8666 Japan Masahiro Jibiki NEC Corporation 1753, Shimonumabe, Nakahara-ku Kawasaki, Kanagawa 211-8666 Japan Suzuki & Jibiki Expires August 5, 2010 [Page 6]