Network Working Group W. Kumari Internet-Draft Google, Inc. Intended status: Informational January 16, 2011 Expires: July 20, 2011 Deprecation of BGP AS_SET, AS_CONFED_SET. draft-ietf-idr-deprecate-as-sets-02.txt Abstract This document deprecates the use of the AS_SET and AS_CONFED_SET types of the AS_PATH in BGPv4. This is done to simplify the design and implementation of the BGP protocol and to make the semantics of the originator of a route more clear. This will also simplify the design, implementation and deployment of bonging work in the Secure Inter-Domain Routing Working Group. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on July 20, 2011. Copyright Notice Copyright (c) 2011 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 Kumari Expires July 20, 2011 [Page 1] Internet-Draft AS_SET, AS_CONFED_SET deprecation January 2011 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3 3. Deployment and modification of behavior . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 7. Normative References . . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5 Kumari Expires July 20, 2011 [Page 2] Internet-Draft AS_SET, AS_CONFED_SET deprecation January 2011 1. Introduction The AS_SET path segment type of the AS_PATH attribute ([RFC4271], Section 4.3) is created by a router that is performing route aggregation and contains an unordered set of ASs that the update has traversed. The AS_CONFED_SET path segment type ([RFC5065]) of the AS_PATH attribute is created by a router that is performing route aggregation and contains an unordered set of Member AS Numbers in the local confederation that the update has traversed (AS_CONFED_SETs are very similar to AS_SETs, but are used within a confederation). By performing aggregation, a router is, in essence, combining multiple routes into a new route. This type of aggregation blurs the semantics of what it means to originate a route. These can cause operational issues that include reachability problems and traffic engineering issues. From analysis of past Internet routing data it is apparent that aggregation that involves AS_SETs is very seldom used in practice on the public network and, when it is, often contains reserved AS numbers ([RFC1930]) and / or only a single AS in the AS_SET. The reduction in table size provided by the aggregation is outweighed by additional complexity in the BGP protocol and confusion regarding what exactly is meant by originating a route. 2. Requirements notation 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 [RFC2119]. 3. Deployment and modification of behavior Operators are strongly advised to not generate any new announcements containing AS_SETs or AS_CONFED_SETs and to withdraw any existing routes containing them as soon as possible. As with any change, the operator should understand the full implications of the change. It is worth noting that new technologies (such as those that take advantage of the "X.509 Extensions for IP Addresses and AS Identifiers" ([RFC3779]) may not support routes with AS_SETs / AS_CONFED_SETs in them, and MAY treat as infeasible routes containing them. Future BGP implementations may also do the same. It is expected that, even before the deployment of these technologies, operators may begin filtering routers that contain Kumari Expires July 20, 2011 [Page 3] Internet-Draft AS_SET, AS_CONFED_SET deprecation January 2011 AS_SETs or AS_CONFED_SETs. 4. IANA Considerations This document contains no IANA considerations. 5. Security Considerations By removing support for the AS_SET path segment type of the AS_PATH attribute future BGP implementations can be simplified. This will also simplify the design and implementation of the RPKI and systems that will rely on it. By removing corner cases we remove complexity and code that is not exercised very often, which decreases the attack surface. 6. Acknowledgements The author would like to thank Tony Li, Randy Bush, John Scudder, Chris Morrow, Danny McPherson, Douglas Montgomery, Enke Chen, Florian Weimer, Ilya Varlashkin, Jakob Heitz, John Leslie, Keyur Patel, Paul Jakma, Rob Austein, Russ Housley, Sandra Murphy, Sriram Kotikalapudi, Steve Bellovin, Steve Kent, Steve Padgett, Alfred Hones, Tom Petch, Alvaro Retana, everyone in IDR and everyone else who provided input. Apologies to those who I may have missed, it was not intentional. 7. Normative References [RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation, selection, and registration of an Autonomous System (AS)", BCP 6, RFC 1930, March 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP Addresses and AS Identifiers", RFC 3779, June 2004. [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous System Confederations for BGP", RFC 5065, August 2007. Kumari Expires July 20, 2011 [Page 4] Internet-Draft AS_SET, AS_CONFED_SET deprecation January 2011 Author's Address Warren Kumari Google, Inc. 1600 Amphitheatre Parkway Mountain View, CA 94043 US Phone: +1 571 748 4373 Email: warren@kumari.net Kumari Expires July 20, 2011 [Page 5]