Network Working Group W. Kumari
Internet-Draft Google, Inc.
Intended status: Informational September 19, 2010
Expires: March 23, 2011
Deprecation of BGP AS_SET, AS_CONFED_SET.
draft-wkumari-deprecate-as-sets-01
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.
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
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This Internet-Draft will expire on March 23, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Deployment and modification of behavior . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
8. Normative References . . . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11
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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
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.
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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].
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3. Terminology
Deprecate: To mark (a component of a software standard) as obsolete
to warn against its use in the future so that it may be phased
out.
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4. Deployment and modification of behavior
It is expected that initially AS_SETs / AS_CONFED_SETs will be
deprecated by the few operators that are currently generating them,
and operator policy changed to filter them. Operators should take
note that new technologies (such as those that make use of the RPKI)
MAY not support routes with AS_SETs / AS_CONFED_SETs in them, and MAY
treat as infeasible routes containing them.
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5. IANA Considerations
This document contains no IANA considerations.
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6. 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.
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7. 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,
and everyone else who provided input.
Apologies to those who I may have missed, it was not intentional.
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8. 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.
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065, August 2007.
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Author's Address
Warren Kumari
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
US
Phone: +1 571 748 4373
Email: warren@kumari.net
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