draft-ietf-idr-deprecate-as-sets-04.txt   draft-ietf-idr-deprecate-as-sets-05.txt 
Network Working Group W. Kumari Network Working Group W. Kumari
Internet-Draft Google, Inc. Internet-Draft Google, Inc.
Intended status: Informational K. Sriram Intended status: BCP K. Sriram
Expires: November 2, 2011 U.S. NIST Expires: January 28, 2012 U.S. NIST
May 1, 2011 July 27, 2011
Deprecation of the use of BGP AS_SET, AS_CONFED_SET. Deprecation of the use of BGP AS_SET, AS_CONFED_SET.
draft-ietf-idr-deprecate-as-sets-04 draft-ietf-idr-deprecate-as-sets-05
Abstract Abstract
This document deprecates the use of the AS_SET and AS_CONFED_SET 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 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 and implementation of the BGP protocol and to make the semantics of
the originator of a route more clear. This will also simplify the the originator of a route more clear. This will also simplify the
design, implementation and deployment of ongoing work in the Secure design, implementation and deployment of ongoing work in the Secure
Inter-Domain Routing Working Group. Inter-Domain Routing Working Group.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 2, 2011. This Internet-Draft will expire on January 28, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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AS_SETs but is used within a confederation. AS_SETs but is used within a confederation.
By performing aggregation, a router is, in essence, combining By performing aggregation, a router is, in essence, combining
multiple existing routes into a single new route. This type of multiple existing routes into a single new route. This type of
aggregation blurs the semantics of what it means to originate a route aggregation blurs the semantics of what it means to originate a route
which can cause operational issues that include reachability problems which can cause operational issues that include reachability problems
and traffic engineering issues. and traffic engineering issues.
From analysis of past Internet routing data it is apparent that From analysis of past Internet routing data it is apparent that
aggregation that involves AS_SETs is very seldom used in practice on aggregation that involves AS_SETs is very seldom used in practice on
the public network and, when it is used, it is usually used the public network [analysis] and, when it is used, it is usually
incorrectly -- reserved AS numbers ([RFC1930]) and / or only a single used incorrectly -- reserved AS numbers ([RFC1930]) and / or only a
AS in the AS_SET are by far the most common case. The reduction in single AS in the AS_SET are by far the most common case. The
table size provided by the aggregation is outweighed by additional reduction in table size provided by the aggregation is outweighed by
complexity in the BGP protocol and confusion regarding what exactly additional complexity in the BGP protocol and confusion regarding
is meant by originating a route. what exactly is meant by originating a route.
In the past AS_SET had been used in a few rare cases to allow route In the past AS_SET had been used in a few rare cases to allow route
aggregation where two or more providers could form the same prefix, aggregation where two or more providers could form the same prefix,
using the exact match of the others prefix in some advertisement and using the exact match of the others prefix in some advertisement and
configuring the aggregation differently elsewhere. The key to configuring the aggregation differently elsewhere. The key to
configuring this correctly was to form the aggregate at the border in configuring this correctly was to form the aggregate at the border in
the outbound BGP policy and omit prefixes from the AS that the the outbound BGP policy and omit prefixes from the AS that the
aggregate was being advertised to. The AS_SET therefore allowed this aggregate was being advertised to. The AS_SET therefore allowed this
practice without the loss of BGP's AS_PATH loop protection. This use practice without the loss of BGP's AS_PATH loop protection. This use
of AS_SET served a purpose which fell in line with the original of AS_SET served a purpose which fell in line with the original
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technologies, operators may begin filtering routes that contain technologies, operators may begin filtering routes that contain
AS_SETs or AS_CONFED_SETs. AS_SETs or AS_CONFED_SETs.
4. IANA Considerations 4. IANA Considerations
This document requires no IANA actions. This document requires no IANA actions.
5. Security Considerations 5. Security Considerations
This document discourages the use of aggregation techniques that This document discourages the use of aggregation techniques that
create AS_SETs. Future work will update the protocol to remove create AS_SETs. Future work may update the protocol to remove
support for the AS_SET path segment type of the AS_PATH attribute. support for the AS_SET path segment type of the AS_PATH attribute.
This will remove complexity and code that is not exercised very This will remove complexity and code that is not exercised very
often, which decreases the attack surface. This will also simplify often, which decreases the attack surface. This will also simplify
the design and implementation of the RPKI and systems that will rely the design and implementation of the RPKI and systems that will rely
on it. on it.
6. Acknowledgements 6. Acknowledgements
The authors would like to thank Tony Li, Randy Bush, John Scudder, The authors would like to thank Tony Li, Randy Bush, John Scudder,
Curtis Villamizar, Danny McPherson, Chris Morrow, Tom Petch, Ilya Curtis Villamizar, Danny McPherson, Chris Morrow, Tom Petch, Ilya
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[RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
Addresses and AS Identifiers", RFC 3779, June 2004. Addresses and AS Identifiers", RFC 3779, June 2004.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006. Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous [RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065, August 2007. System Confederations for BGP", RFC 5065, August 2007.
[analysis]
Sriram, K., "Measurement Data on AS_SET and AGGREGATOR,
SIDR WG presentation, IETF-78", July 2010, < http://
www.antd.nist.gov/~ksriram/AS_SET_Aggregator_Stats.pdf>.
Authors' Addresses Authors' Addresses
Warren Kumari Warren Kumari
Google, Inc. Google, Inc.
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
Mountain View, CA 94043 Mountain View, CA 94043
US US
Phone: +1 571 748 4373 Phone: +1 571 748 4373
Email: warren@kumari.net Email: warren@kumari.net
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