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.
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This Internet-Draft will expire on March 4, 2011.
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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
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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].
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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.
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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.
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4. IANA Considerations
This document contains no IANA considerations.
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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.
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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.
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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.
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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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