Network Working Group D. Rao Internet-Draft P. Mohapatra Intended status: Standards Track Cisco Systems Expires: April 29, 2010 J. Haas Arbor Networks October 26, 2009 Generic Subtype for BGP Four-octet AS specific extended community draft-ietf-idr-as4octet-extcomm-generic-subtype-01.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 April 29, 2010. 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. Abstract Maintaining the current best practices with communities, ISPs and Rao, et al. Expires April 29, 2010 [Page 1] Internet-Draft 4octet extcomm generic sub-type October 2009 enterprises that are assigned a 4-octet AS number may want the BGP UPDATE messages they receive from their customers or peers to include a 4-octet AS specific extended community. This document defines a new sub-type within the four-octet AS specific extended community to facilitate this practice. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 2. Generic Sub-type Definition . . . . . . . . . . . . . . . . . . 3 3. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Rao, et al. Expires April 29, 2010 [Page 2] Internet-Draft 4octet extcomm generic sub-type October 2009 1. Introduction Maintaining the current best practices with communities, ISPs and enterprises that are assigned a 4-octet AS number may want the BGP UPDATE messages they receive from their customers or peers to include a 4-octet AS specific extended community. This document defines a new sub-type within the four-octet AS specific extended community to facilitate this practice. For example, [RFC1998] describes an application of BGP community attribute ([RFC1997]) to implement flexible routing policies for sites multi-homed to one or multiple providers. In a two-octet AS environment, the advertised routes are usually associated with a community attribute that encodes the provider's AS number in the first two octets of the community and a LOCAL_PREF value in the second two octets of the community. The community attribute signals the provider edge routers connected to the site to set the corresponding LOCAL_PREF on their advertisements to the IBGP mesh. In this way, customers can put into practice topologies like active- backup. When such a provider is assigned a four-octet AS number, the existing mechanism of using communities is not sufficient since the AS portion of the RFC 1997 community cannot exceed two bytes. The natural alternative is to extend the same mechanism using extended communities since it allows for encoding eight bytes of information. [I-D.ietf-l3vpn-as4octet-ext-community] defines a format for a four- octet AS specific extended community with a designated type field. That document defines two sub-types: Four-octet specific Route Target extended community and Four-octet specific Route Origin extended community. This document specifies a generic sub-type for the four- octet AS specific extended community to provide benefits such as the one cited above as the Internet migrates to four-octet AS space. 1.1. 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]. 2. Generic Sub-type Definition Rao, et al. Expires April 29, 2010 [Page 3] Internet-Draft 4octet extcomm generic sub-type October 2009 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x02 or 0x42 | 0x04 | Global | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Administrator | Local Administrator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ This is an extended type with Type Field comprising of 2 octets and Value Field comprising of 6 octets. The high-order octet of this extended type is set to either 0x02 (for transitive communities) or 0x42 (for non-transitive communities). The low-order octet or the sub-type is set to 0x04. The Value Field consists of two sub-fields: Global Administrator sub-field: 4 octets This sub-field contains a four-octet Autonomous System number. Local Administrator sub-field: 2 octets This sub-field contains a value that can influence routing policies. This value has semantics that are of significance for the Autonomous System in the Global Administrator field. 3. Deployment Considerations There are situations in peering where a 4-octet AS specific generic extended community cannot be used. A speaker with a 4-octet AS may not support 4-octet extended communities; or the speaker may have a customer or peer that does not support 4-octet extended communities. In all such cases, the speaker may need to define an appropriate standard community value for the same purpose. As an example, a peer may tag its routes with communities that encode AS_TRANS [RFC4893] as the first two octets. Similarly, a 2-octet AS number may have two valid representations as either a standard community or a 4-octet extended community with the upper two octets of the AS number set to zero. For backward compatibility with existing deployments, and to avoid inconsistencies between standard communities and 4-octet extended communities, two- octet ASes SHOULD use standard 2-octet communities as defined in RFC 1997 rather than the 4-octet AS specific community as defined in this document. Rao, et al. Expires April 29, 2010 [Page 4] Internet-Draft 4octet extcomm generic sub-type October 2009 4. Acknowledgments The authors would like to thank Paul Jakma, Bruno Decraene and Cayle Spandon for their useful comments on the document. 5. IANA Considerations This document defines a specific application of the four-octet AS specific extended community. IANA is requested to to assign a sub- type value of 0x04 for the generic four-octet AS specific extended community. This document makes the following assignments for the generic four- octet AS specific extended community: Name Value ---- ----- transitive generic four-octet AS specific 0x0204 non-transitive generic four-octet AS specific 0x4204 6. Security Considerations There are no additional security risks introduced by this design. 7. Normative References [I-D.ietf-l3vpn-as4octet-ext-community] Rekhter, Y., Sangli, S., and D. Tappan, "Four-octet AS Specific BGP Extended Community", draft-ietf-l3vpn-as4octet-ext-community-03 (work in progress), March 2009. [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP Communities Attribute", RFC 1997, August 1996. [RFC1998] Chen, E. and T. Bates, "An Application of the BGP Community Attribute in Multi-home Routing", RFC 1998, August 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, February 2006. Rao, et al. Expires April 29, 2010 [Page 5] Internet-Draft 4octet extcomm generic sub-type October 2009 [RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS Number Space", RFC 4893, May 2007. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Authors' Addresses Dhananjaya Rao Cisco Systems 170 W. Tasman Drive San Jose, CA 95134 USA Email: dhrao@cisco.com Pradosh Mohapatra Cisco Systems 170 W. Tasman Drive San Jose, CA 95134 USA Email: pmohapat@cisco.com Jeffrey Haas Arbor Networks 2727 S. State St. Ann Arbor, MI 48104 USA Email: jhaas@arbor.net Rao, et al. Expires April 29, 2010 [Page 6]