Recommendation for Not Using AS_SET and AS_CONFED_SET in BGP
RFC 6472
Document | Type |
RFC - Best Current Practice
(December 2011; No errata)
Also known as BCP 172
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Authors | Kotikalapudi Sriram , Warren Kumari | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 6472 (Best Current Practice) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Stewart Bryant | ||
Send notices to | (None) |
Internet Engineering Task Force (IETF) W. Kumari Request for Comments: 6472 Google, Inc. BCP: 172 K. Sriram Category: Best Current Practice U.S. NIST ISSN: 2070-1721 December 2011 Recommendation for Not Using AS_SET and AS_CONFED_SET in BGP Abstract This document recommends against 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 BGP and to make the semantics of the originator of a route more clear. This will also simplify the design, implementation, and deployment of ongoing work in the Secure Inter-Domain Routing Working Group. Status of This Memo This memo documents an Internet Best Current Practice. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on BCPs is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6472. 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 described in the Simplified BSD License. Kumari & Sriram Best Current Practice [Page 1] RFC 6472 AS_SET, AS_CONFED_SET Use Deprecation December 2011 Table of Contents 1. Introduction ....................................................2 2. Requirements Notation ...........................................3 3. Recommendation to Network Operators .............................3 4. Security Considerations .........................................4 5. Acknowledgements ................................................4 6. References ......................................................4 6.1. Normative References .......................................4 6.2. Informative References .....................................4 1. Introduction The AS_SET path segment type of the AS_PATH attribute (Sections 4.3 and 5.1.2 of [RFC4271]) is created by a router that is performing route aggregation and contains an unordered set of Autonomous Systems (ASes) that the update has traversed. The AS_CONFED_SET path 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. It is very similar to AS_SETs but is used within a confederation. By performing aggregation, a router is, in essence, combining multiple existing routes into a single new route. This type of aggregation blurs the semantics of what it means to originate a route. Said aggregation can therefore cause operational issues, such as not being able to authenticate a route origin for the aggregate prefix in new BGP security technologies (such as those that take advantage of the "X.509 Extensions for IP Addresses and AS Identifiers" [RFC3779]). This in turn would result in reachability problems for the aggregated prefix and its components (i.e., more specifics). Said aggregation also creates traffic engineering issues, because the precise path information for the component prefixes is not preserved. 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 [Analysis] and, when it is used, it is usually used incorrectly -- reserved AS numbers ([RFC1930]) and/or only a single AS in the AS_SET are by far the most common case. Because the aggregation involving AS_SETs is very rarely used, the reduction in table size provided by said aggregation is extremely small, and any advantage thereof is outweighed by additional complexity in BGP. As noted above, said aggregation also poses impediments to implementation of said new BGP security technologies. Kumari & Sriram Best Current Practice [Page 2] RFC 6472 AS_SET, AS_CONFED_SET Use Deprecation December 2011Show full document text