Network Working Group W. Kumari Internet-Draft Google, Inc. Intended status: Informational August 31, 2010 Expires: March 4, 2011 Deprecation of BGP AS_SET. draft-wkumari-deprecate-as-sets-00 Abstract This document deprecates the use of the AS_SET type of the AS_PATH in BGPv4. This is done to simply the design and implementation of the BGP protocol and to make the semantics of the originator of a route more clear. 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 March 4, 2011. 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 Simplified BSD License. Kumari Expires March 4, 2011 [Page 1] Internet-Draft Deprecation of BGP AS_SET. August 2010 Table of Contents 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Deployment and modification of behavior . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 7. Normative References . . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10 Kumari Expires March 4, 2011 [Page 2] Internet-Draft Deprecation of BGP AS_SET. August 2010 1. 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]. Kumari Expires March 4, 2011 [Page 3] Internet-Draft Deprecation of BGP AS_SET. August 2010 2. 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. By performing aggregation, a router is, in essence, combining multiple routes into a new route. The RPKI ([I-D.ietf-sidr-arch]) provides a cryptographic means to validate that a specific AS is authorized to announce a specific network. The creation of an aggregate that contains an AS_SET means that the aggregating router is originating a route for address space that it cannot cryptographically prove that it is authorized to originate. While it may be possible to include the route origin attestations (ROA) from all of the routes that contribute to the aggregate into the aggregate, this ends up being messy, inelegant and has partial states that suck caterpillar snot! From analysis of past Internet routing dumps it is apparent that aggregation that involves AS_SETs is almost never used in practice and, when it is usually contains reserved AS numbers ([RFC1930]) and / or only a single AS in the AS_SET. The reductions 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. Kumari Expires March 4, 2011 [Page 4] Internet-Draft Deprecation of BGP AS_SET. August 2010 3. Deployment and modification of behavior It is expected that initially AS_SETs will be deprecated by the few operators that are currently generating them, and operator policy changing to filter them. Over time BGP implementations MAY no longer support generating them, and eventually implementations MAY quietly ignore updates with AS_SETs in them . Operators should take note that new protocols (such as those that make use of the RPKI) are likely to not work with AS_SETs and may ignore routes (treat as infeasible) containing them. Kumari Expires March 4, 2011 [Page 5] Internet-Draft Deprecation of BGP AS_SET. August 2010 4. IANA Considerations This document contains no IANA considerations. Kumari Expires March 4, 2011 [Page 6] Internet-Draft Deprecation of BGP AS_SET. August 2010 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. Kumari Expires March 4, 2011 [Page 7] Internet-Draft Deprecation of BGP AS_SET. August 2010 6. Acknowledgements The author would like to thank Randy Bush, Steve Bellovin, Russ Housley, Steve Kent, Sandra Murphy, John Scudder, Sriram Kotikalapudi, Chris Morrow, Rob Austein, Douglas Montgomery, Keyur Patel, and everyone else who provided input. Apologies to those who I may have missed. Kumari Expires March 4, 2011 [Page 8] Internet-Draft Deprecation of BGP AS_SET. August 2010 7. Normative References [I-D.ietf-sidr-arch] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure Internet Routing", draft-ietf-sidr-arch-09 (work in progress), October 2009. [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. [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. Kumari Expires March 4, 2011 [Page 9] Internet-Draft Deprecation of BGP AS_SET. August 2010 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 March 4, 2011 [Page 10]