< draft-kumari-deprecate-as-set-confed-set-13.txt		draft-kumari-deprecate-as-set-confed-set-14.txt >
	Network Working Group W. Kumari		Network Working Group W. Kumari
	Internet-Draft Google, Inc.		Internet-Draft Google, Inc.
	Intended status: Standards Track K. Sriram		Intended status: Standards Track K. Sriram
	Expires: July 21, 2019 USA NIST		Expires: February 6, 2020 USA NIST
	January 17, 2019		August 5, 2019
	Deprecation of AS_SET and AS_CONFED_SET in BGP		Deprecation of AS_SET and AS_CONFED_SET in BGP
	draft-kumari-deprecate-as-set-confed-set-13		draft-kumari-deprecate-as-set-confed-set-14
	Abstract		Abstract
	RFC 6472 (i.e., BCP 172) recommends not using AS_SET and		BCP 172 (i.e., RFC 6472) recommends not using AS_SET and
	AS_CONFED_SET in BGP. This document updates RFC 4271 and proscribes		AS_CONFED_SET in Border Gateway Protocol (BGP). This document
	the use of the AS_SET and AS_CONFED_SET types of the AS_PATH in		updates RFC 4271 and proscribes the use of the AS_SET and
	BGPv4. This is done to simplify the design and implementation of BGP		AS_CONFED_SET types of path segments in the AS_PATH. This is done to
	and to make the semantics of the originator of a route more clear.		simplify the design and implementation of BGP and to make the
	This will also simplify the design, implementation, and deployment of		semantics of the originator of a route clearer. This will also
	ongoing work in the Secure Inter-Domain Routing Working Group.		simplify the design, implementation, and deployment of various BGP
			security mechanisms.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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-
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	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
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	This Internet-Draft will expire on July 21, 2019.		This Internet-Draft will expire on February 6, 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
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	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3		2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
	3. Recommendation to Network Operators . . . . . . . . . . . . . 3		3. Recommendation to Network Operators . . . . . . . . . . . . . 3
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 4		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4		6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4		7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
	7.1. Normative References . . . . . . . . . . . . . . . . . . 4		7.1. Normative References . . . . . . . . . . . . . . . . . . 4
	7.2. Informative References . . . . . . . . . . . . . . . . . 5		7.2. Informative References . . . . . . . . . . . . . . . . . 5
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
	1. Introduction		1. Introduction
	RFC 6472 (i.e., BCP 172) [RFC6472] makes a recommendation for not		BCP 172 [RFC6472] makes a recommendation for not using AS_SET and
	using AS_SET and AS_CONFED_SET in BGP. This document advances the		AS_CONFED_SET in Border Gateway Protocol (BGP). This document
	recommendation to a standards requirement in BGP. It updates RFC		advances the recommendation to a standards requirement in BGP. It
	4271 and proscribes the use of the AS_SET and AS_CONFED_SET types of		updates [RFC4271] and proscribes the use of the AS_SET and
	the AS_PATH in BGPv4.		AS_CONFED_SET types of path segments in the AS_PATH.
	The AS_SET path segment type of the AS_PATH attribute (Sections 4.3		The AS_SET path segment in the AS_PATH attribute (Sections 4.3 and
	and 5.1.2 of [RFC4271]) is created by a router that is performing		5.1.2 of [RFC4271]) is created by a router that is performing route
	route aggregation and contains an unordered set of Autonomous Systems		aggregation and contains an unordered set of Autonomous Systems
	(ASes) that the update has traversed. The AS_CONFED_SET path type		(ASes) that the update has traversed. The AS_CONFED_SET path segment
	([RFC5065]) of the AS_PATH attribute is created by a router that is		(see [RFC5065]) in the AS_PATH attribute is created by a router that
	performing route aggregation and contains an unordered set of Member		is performing route aggregation and contains an unordered set of
	AS Numbers in the local confederation that the update has traversed.		Member AS Numbers in the local confederation that the update has
	It is very similar to AS_SETs but is used within a confederation.		traversed. It is very similar to AS_SETs but is used within a
			confederation.
	By performing aggregation, a router is, in essence, combining		By performing aggregation, a router is combining multiple existing
	multiple existing routes into a single new route. This type of		routes into a single new route. The aggregation together with the
	aggregation blurs the semantics of what it means to originate a		use of AS_SET blurs the semantics of origin AS for the prefix being
	route. Said aggregation can therefore cause operational issues, such		announced. Therefore, the aggregation with AS_SET (or AS_CONFED_SET)
	as not being able to authenticate a route origin for the aggregate		can cause operational issues, such as not being able to authenticate
	prefix in new BGP security technologies (such as those that take		a route origin for the aggregate prefix in new BGP security
	advantage of the "X.509 Extensions for IP Addresses and AS		technologies such as those that take advantage of X.509 extensions
	Identifiers" [RFC3779]). This in turn would result in reachability		for IP addresses and AS identifiers [RFC3779] [RFC6811] [RFC8205].
	problems for the aggregated prefix and its components (i.e., more		This in turn could result in reachability problems for the aggregated
	specifics). Said aggregation also creates traffic engineering		prefix and its components (i.e., more-specific prefixes). The
			aggregation as described above could also create traffic engineering
	issues, because the precise path information for the component		issues, because the precise path information for the component
	prefixes is not preserved.		prefixes are not preserved.
	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 [Analysis] and, when it is used, it is usually		the public Internet [Analysis] and when it is used, it is often used
	used incorrectly -- reserved AS numbers ([RFC1930]) and/or only a		incorrectly -- reserved AS numbers ([RFC1930]) and/or only a single
	single AS in the AS_SET are by far the most common case. Because the		AS in the AS_SET are by far the most common cases. Because the
	aggregation involving AS_SETs is very rarely used, the reduction in		aggregation involving AS_SETs is very rarely used, the reduction in
	table size provided by said aggregation is extremely small, and any		table size provided by said aggregation is extremely small, and any
	advantage thereof is outweighed by additional complexity in BGP. As		advantage thereof is outweighed by additional complexity in BGP. As
	noted above, said aggregation also poses impediments to		noted above, said aggregation also poses impediments to
	implementation of said new BGP security technologies.		implementation of new BGP security technologies.
	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 aggregate
	using the exact match of the other's prefix in some advertisement and		prefix, using the exact match of the other's aggregate prefix in some
	configuring the aggregation differently elsewhere. The key to		advertisement and configuring the aggregation differently elsewhere.
	configuring this correctly was to form the aggregate at the border in		The key to configuring this correctly was to form the aggregate at
	the outbound BGP policy and omit prefixes from the AS that the		the border in the outbound BGP policy and omit prefixes from the AS
	aggregate was being advertised to. The AS_SET therefore allowed this		that the aggregate was being advertised to. The AS_SET therefore
	practice without the loss of BGP's AS_PATH loop protection. This use		allowed this practice without the loss of BGP's AS_PATH loop
	of AS_SET served a purpose that fell in line with the original		protection. This use of AS_SET served a purpose that fell in line
	intended use. Without the use of AS_SET, aggregates must always		with the original intended use. Without the use of AS_SET,
	contain only less specific prefixes (not less than or equal to), and		aggregates must always contain only less-specific prefixes (not less
	must never aggregate an exact match.		than or equal to) and must never aggregate an exact match.
	2. Requirements Notation		2. Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	document are to be interpreted as described in [RFC2119].		"OPTIONAL" in this document are to be interpreted as described in BCP
			14 [RFC2119] [RFC8174] when, and only when, they appear in all
			capitals, as shown here.
	3. Recommendation to Network Operators		3. Recommendation to Network Operators
	Operators MUST NOT generate any new announcements containing AS_SETs		Operators MUST NOT generate any new announcements containing AS_SETs
	or AS_CONFED_SETs. If they have already announced routes with		or AS_CONFED_SETs. If they have already announced routes with
	AS_SETs or AS_CONFED_SETs in them, then they MUST withdraw those		AS_SETs or AS_CONFED_SETs in them, then they MUST withdraw those
	routes and re-announce routes for the component prefixes (i.e., the		routes and re-announce routes for the component prefixes (i.e., the
	more-specifics of the previously aggregated prefix) without AS_SETs		more-specific prefixes subsumed by the previously aggregated prefix)
	or CONFED_SETs in the updates. This involves undoing the aggregation		without AS_SETs or CONFED_SETs in the updates. Route aggregation
	that was previously performed (with AS_SETs/CONFED_SETs), and		that was previously performed by proxy aggregation (i.e., without the
	announcing more specifics (without AS_SETs/CONFED_SETs). Route		use of AS_SETs) is still possible under some conditions. When doing
	aggregation that was previously performed by proxy aggregation (i.e.,		this, operators MUST form the aggregate at the border in the outbound
	without the use of AS_SETs) is still possible under some conditions.		BGP policy and omit any prefixes from the AS that the aggregate was
	As with any change, the operator should understand the full		being advertised to. As with any change, the operator should
	implications of the change.		understand the full implications of the change.
	It is worth noting that new technologies (such as those that take		It is worth noting that new BGP security technologies (such as those
	advantage of the "X.509 Extensions for IP Addresses and AS		that take advantage of X.509 extensions for IP addresses and AS
	Identifiers" [RFC3779]) might not support routes with AS_SETs/		identifiers [RFC3779] [RFC6811] [RFC8205]) might not support routes
	AS_CONFED_SETs in them, and may treat as infeasible routes containing		with AS_SETs/AS_CONFED_SETs in them, and may treat routes containing
	them. Future BGP implementations may also do the same. It is		them as infeasible. Future BGP implementations may also do the same.
	expected that, even before the deployment of these new or future		It is expected that, even before the deployment of these new or
	technologies, operators may filter routes with AS_SETs/AS_CONFED_SETs		future technologies, operators may filter routes with AS_SETs/
	in them. Other than making that observation, this document is not		AS_CONFED_SETs in them. Other than making that observation, this
	intended to make any recommendation for how an operator should behave		document is not intended to make any recommendation for how an
	when receiving a route with AS_SET or AS_CONFED_SET in it. This		implementation should behave when receiving a route with AS_SET or
	document's focus is entirely on the sender side, as discussed in the		AS_CONFED_SET in it. This document's focus is entirely on the sender
	preceding paragraph.		side, as discussed in the preceding paragraph.
	4. IANA Considerations		4. Security Considerations
	This document requires no IANA actions.		This document obsoletes the use of aggregation techniques that create
			AS_SETs or AS_CONFED_SETs. Obsoleting these path segment types from
			BGP and removal of the related code from implementations would
			potentially decrease the attack surface for BGP.
	5. Security Considerations		5. IANA Considerations
	This document obsoletes the use of aggregation techniques that create		This document requires no IANA actions.
	AS_SETs or AS_CONFED_SETs. Future work, intended for securing BGP,
	may update the protocol to remove support for the AS_SET and
	AS_CONFED_SET path segment type of the AS_PATH attribute. This
	future work will remove complexity and code that are not exercised
	very often, thereby decreasing the attack surface.
	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, and Ilya		Curtis Villamizar, Danny McPherson, Chris Morrow, Tom Petch, Ilya
	Varlashkin, as well as Douglas Montgomery, Enke Chen, Florian Weimer,		Varlashkin, Douglas Montgomery, Enke Chen, Florian Weimer, Jakob
	Jakob Heitz, John Leslie, Keyur Patel, Paul Jakma, Rob Austein, Russ		Heitz, John Leslie, Keyur Patel, Paul Jakma, Rob Austein, Russ
	Housley, Sandra Murphy, Steve Bellovin, Steve Kent, Steve Padgett,		Housley, Sandra Murphy, Steve Bellovin, Steve Kent, Steve Padgett,
	Alfred Hoenes, Alvaro Retana, everyone in the IDR working group, and		Alfred Hoenes, and Alvaro Retana.
	everyone else who provided input.
	Apologies to those who we may have missed; it was not intentional.
	7. References		7. References
	7.1. Normative References		7.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
			[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
			Border Gateway Protocol 4 (BGP-4)", RFC 4271,
			DOI 10.17487/RFC4271, January 2006,
			<https://www.rfc-editor.org/info/rfc4271>.
			[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
			System Confederations for BGP", RFC 5065,
			DOI 10.17487/RFC5065, August 2007,
			<https://www.rfc-editor.org/info/rfc5065>.
	7.2. Informative References		7.2. Informative References
	[Analysis]		[Analysis]
	Sriram, K. and D. Montgomery, "Measurement Data on AS_SET		Sriram, K. and D. Montgomery, "Measurement Data on AS_SET
	and AGGREGATOR: Implications for {Prefix, Origin}		and AGGREGATOR: Implications for {Prefix, Origin}
	Validation Algorithms", SIDR WG presentation, IETF 78,		Validation Algorithms", SIDR WG presentation, IETF 78,
	July 2010, <http://www.nist.gov/itl/antd/upload/		July 2010, <http://www.nist.gov/itl/antd/upload/
	AS_SET_Aggregator_Stats.pdf>.		AS_SET_Aggregator_Stats.pdf>.
	[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,		[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,
	selection, and registration of an Autonomous System (AS)",		selection, and registration of an Autonomous System (AS)",
	BCP 6, RFC 1930, DOI 10.17487/RFC1930, March 1996,		BCP 6, RFC 1930, DOI 10.17487/RFC1930, March 1996,
	<https://www.rfc-editor.org/info/rfc1930>.		<https://www.rfc-editor.org/info/rfc1930>.
	[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,		Addresses and AS Identifiers", RFC 3779,
	DOI 10.17487/RFC3779, June 2004,		DOI 10.17487/RFC3779, June 2004,
	<https://www.rfc-editor.org/info/rfc3779>.		<https://www.rfc-editor.org/info/rfc3779>.
	[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
	Border Gateway Protocol 4 (BGP-4)", RFC 4271,
	DOI 10.17487/RFC4271, January 2006,
	<https://www.rfc-editor.org/info/rfc4271>.
	[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
	System Confederations for BGP", RFC 5065,
	DOI 10.17487/RFC5065, August 2007,
	<https://www.rfc-editor.org/info/rfc5065>.
	[RFC6472] Kumari, W. and K. Sriram, "Recommendation for Not Using		[RFC6472] Kumari, W. and K. Sriram, "Recommendation for Not Using
	AS_SET and AS_CONFED_SET in BGP", BCP 172, RFC 6472,		AS_SET and AS_CONFED_SET in BGP", BCP 172, RFC 6472,
	DOI 10.17487/RFC6472, December 2011,		DOI 10.17487/RFC6472, December 2011,
	<https://www.rfc-editor.org/info/rfc6472>.		<https://www.rfc-editor.org/info/rfc6472>.
			[RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
			Austein, "BGP Prefix Origin Validation", RFC 6811,
			DOI 10.17487/RFC6811, January 2013,
			<https://www.rfc-editor.org/info/rfc6811>.
			[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
			2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
			May 2017, <https://www.rfc-editor.org/info/rfc8174>.
			[RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
			Specification", RFC 8205, DOI 10.17487/RFC8205, September
			2017, <https://www.rfc-editor.org/info/rfc8205>.
	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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