Internet DRAFT - draft-wkumari-deprecate-as-sets

draft-wkumari-deprecate-as-sets






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
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   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.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.




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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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