< draft-ietf-idr-deprecate-as-set-confed-set-00.txt		draft-ietf-idr-deprecate-as-set-confed-set-01.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		Obsoletes: 6472 (if approved) K. Sriram
	Expires: March 6, 2020 USA NIST		Updates: 4271 5065 (if approved) L. Hannachi
	September 3, 2019		Intended status: Standards Track USA NIST
			Expires: May 1, 2020 October 29, 2019
	Deprecation of AS_SET and AS_CONFED_SET in BGP		Deprecation of AS_SET and AS_CONFED_SET in BGP
	draft-ietf-idr-deprecate-as-set-confed-set-00		draft-ietf-idr-deprecate-as-set-confed-set-01
	Abstract		Abstract
	BCP 172 (i.e., RFC 6472) recommends not using AS_SET and		BCP 172 (i.e., RFC 6472) recommends not using AS_SET and
	AS_CONFED_SET in Border Gateway Protocol (BGP). This document		AS_CONFED_SET in the Border Gateway Protocol. This document advances
	updates RFC 4271 and proscribes the use of the AS_SET and		this recommendation to a standards requirement in BGP; it proscribes
	AS_CONFED_SET types of path segments in the AS_PATH. This is done to		the use of the AS_SET and AS_CONFED_SET types of path segments in the
	simplify the design and implementation of BGP and to make the		AS_PATH. This is done to simplify the design and implementation of
	semantics of the originator of a route clearer. This will also		BGP and to make the semantics of the originator of a route clearer.
	simplify the design, implementation, and deployment of various BGP		This will also simplify the design, implementation, and deployment of
	security mechanisms.		various BGP security mechanisms. This document (if approved) updates
			RFC 4271 and RFC 5065 by eliminating AS_SET and AS_CONFED_SET types,
			and obsoletes RFC 6472.
	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-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://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 March 6, 2020.		This Internet-Draft will expire on May 1, 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.
	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
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://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
	skipping to change at page 2, line 14 ¶		skipping to change at page 2, line 17 ¶
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	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 Language . . . . . . . . . . . . . . . . . . . . 3		2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
	3. Recommendation to Network Operators . . . . . . . . . . . . . 3		3. Recommendation to Network Operators . . . . . . . . . . . . . 3
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 4		4. Updates to Existing RFCs . . . . . . . . . . . . . . . . . . 4
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
	7.1. Normative References . . . . . . . . . . . . . . . . . . 4		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
	7.2. Informative References . . . . . . . . . . . . . . . . . 5		8.1. Normative References . . . . . . . . . . . . . . . . . . 5
			8.2. Informative References . . . . . . . . . . . . . . . . . 5
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
	1. Introduction		1. Introduction
	BCP 172 [RFC6472] makes a recommendation for not using AS_SET and		BCP 172 [RFC6472] makes a recommendation for not using AS_SET (see
	AS_CONFED_SET in Border Gateway Protocol (BGP). This document		[RFC4271]) and AS_CONFED_SET (see [RFC5065]) in the Border Gateway
	advances the recommendation to a standards requirement in BGP. It		Protocol (BGP). This document advances the BCP recommendation to a
	updates [RFC4271] and proscribes the use of the AS_SET and		standards requirement in BGP; it proscribes the use of the AS_SET and
	AS_CONFED_SET types of path segments in the AS_PATH.		AS_CONFED_SET types of path segments in the AS_PATH.
	The AS_SET path segment in the AS_PATH attribute (Sections 4.3 and		The AS_SET path segment in the AS_PATH attribute (Sections 4.3 and
	5.1.2 of [RFC4271]) is created by a router that is performing route		5.1.2 of [RFC4271]) is created by a router that is performing 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 segment		(ASes) that the update has traversed. The AS_CONFED_SET path segment
	(see [RFC5065]) in the AS_PATH attribute is created by a router that		(see [RFC5065]) in the AS_PATH attribute is created by a router that
	is performing route aggregation and contains an unordered set of		is performing route aggregation and contains an unordered set of
	Member AS Numbers in the local confederation that the update has		Member AS Numbers in the local confederation that the update has
	traversed. It is very similar to AS_SETs but is used within a		traversed. It is very similar to AS_SETs but is used within a
	confederation.		confederation.
	By performing aggregation, a router is combining multiple existing		By performing aggregation, a router is combining multiple existing
	routes into a single new route. The aggregation together with the		routes into a single new route. The aggregation together with the
	use of AS_SET blurs the semantics of origin AS for the prefix being		use of AS_SET blurs the semantics of origin AS for the prefix being
	announced. Therefore, the aggregation with AS_SET (or AS_CONFED_SET)		announced. Therefore, the aggregation with AS_SET (or AS_CONFED_SET)
	can cause operational issues, such as not being able to authenticate		can cause operational issues, such as not being able to authenticate
	a route origin for the aggregate prefix in new BGP security		a route origin for the aggregate prefix in new BGP security
	technologies such as those that take advantage of X.509 extensions		technologies such as those that take advantage of X.509 extensions
	for IP addresses and AS identifiers [RFC3779] [RFC6811] [RFC8205].		for IP addresses and AS identifiers [RFC3779] [RFC6480] [RFC6811]
	This in turn could result in reachability problems for the aggregated
	prefix and its components (i.e., more-specific prefixes). The		[RFC8205]. This in turn could result in reachability problems for
	aggregation as described above could also create traffic engineering		the aggregated prefix and its components (i.e., more-specific
	issues, because the precise path information for the component		prefixes). The aggregation as described above could also create
	prefixes are not preserved.		traffic engineering issues, because the precise path information for
			the component 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 Internet [Analysis] and when it is used, it is often used		the public Internet [Analysis] and when it is used, it is often used
	incorrectly -- reserved AS numbers ([RFC1930]) and/or only a single		incorrectly -- only a single AS in the AS_SET are by far the most
	AS in the AS_SET are by far the most common cases. Because the		common cases. Also, very often the same AS appears in the
	aggregation involving AS_SETs is very rarely used, the reduction in		AS_SEQUENCE and the AS_SET in the BGP update. The occurrence of
	table size provided by said aggregation is extremely small, and any		reserved AS numbers ([IANA-SP-ASN]) is also somewhat frequent.
			Because the aggregation involving AS_SETs is very rarely used, the
			reduction in table size provided by this 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, AS_SETs also pose impediments to implementation of new
	implementation of new BGP security technologies.		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 aggregate		aggregation where two or more providers could form the same aggregate
	prefix, using the exact match of the other's aggregate prefix in some		prefix, using the exact match of the other's aggregate prefix in some
	advertisement and configuring the aggregation differently elsewhere.		advertisement and configuring the aggregation differently elsewhere.
	The key to configuring this correctly was to form the aggregate at		The key to configuring this correctly was to form the aggregate at
	the border in the outbound BGP policy and omit prefixes from the AS		the border in the outbound BGP policy and omit prefixes from the AS
	that the aggregate was being advertised to. The AS_SET therefore		that the aggregate was being advertised to. The AS_SET therefore
	allowed this practice without the loss of BGP's AS_PATH loop		allowed this practice without the loss of BGP's AS_PATH loop
	protection. This use of AS_SET served a purpose that fell in line		protection. This use of AS_SET served a purpose that fell in line
	skipping to change at page 3, line 41 ¶		skipping to change at page 3, line 47 ¶
	2. Requirements Language		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", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in BCP		"OPTIONAL" in this document are to be interpreted as described in BCP
	14 [RFC2119] [RFC8174] when, and only when, they appear in all		14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	3. Recommendation to Network Operators		3. Recommendation to Network Operators
	Operators MUST NOT generate any new announcements containing AS_SETs		Network operators MUST NOT generate any new announcements containing
	or AS_CONFED_SETs. If they have already announced routes with		AS_SETs or AS_CONFED_SETs. If they have already announced routes
	AS_SETs or AS_CONFED_SETs in them, then they MUST withdraw those		with 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-specific prefixes subsumed by the previously aggregated prefix)		more-specific routes subsumed by the previously aggregated route)
	without AS_SETs or CONFED_SETs in the updates. Route aggregation		without AS_SETs or AS_CONFED_SETs in the updates. A sending router
	that was previously performed by proxy aggregation (i.e., without the		MUST not generate a BGP UPDATE with AS_SET or AS_CONFED_SET. A
	use of AS_SETs) is still possible under some conditions. When doing		receiving router MUST treat the announced routes in a BGP UPDATE with
	this, operators MUST form the aggregate at the border in the outbound		AS_SET or AS_CONFED_SET as withdrawn routes.
	BGP policy and omit any prefixes from the AS that the aggregate was
	being advertised to. As with any change, the operator should		If a network operator wishes to consider a BGP UPDATE with AS_SET or
	understand the full implications of the change.		AS_CONFED_SET for path selection, they MAY have a feature (knob) in
			the router to opt to do so. The operator should understand the full
			implications of choosing this option.
			Route aggregation that was previously performed by proxy aggregation
			without the use of AS_SETs is still possible under some conditions.
			When doing this, operators MUST form the aggregate at the border in
			the outbound BGP policy and omit any prefixes from the AS that the
			aggregate is being advertised to. As with any change, the operator
			should understand the full implications of the change.
	It is worth noting that new BGP security technologies (such as those		It is worth noting that new BGP security technologies (such as those
	that take advantage of X.509 extensions for IP addresses and AS		that take advantage of X.509 extensions for IP addresses and AS
	identifiers [RFC3779] [RFC6811] [RFC8205]) might not support routes		identifiers [RFC3779] [RFC6480] [RFC6811] [RFC8205]) might not
	with AS_SETs/AS_CONFED_SETs in them, and may treat routes containing		support routes with AS_SETs/AS_CONFED_SETs in them, and may treat
	them as infeasible. Future BGP implementations may also do the same.		routes containing them as infeasible even before the updated BGP in
	It is expected that, even before the deployment of these new or		this document is implemented.
	future technologies, operators may filter routes with AS_SETs/
	AS_CONFED_SETs in them. Other than making that observation, this
	document is not intended to make any recommendation for how an
	implementation should behave when receiving a route with AS_SET or
	AS_CONFED_SET in it. This document's focus is entirely on the sender
	side, as discussed in the preceding paragraph.
	4. Security Considerations		4. Updates to Existing RFCs
			This document eliminates AS_PATH segment type 1, namely, AS_SET that
			is specified in Section 4.3 of [RFC4271]. That is, in a future
			specification of BGP -- one that would obsolete RFC 4271 -- the use
			of AS_SET will not be specified.
			This document also eliminates AS_PATH segment type 4, namely,
			AS_CONFED_SET that is specified in Section 3 of [RFC5065]. That is,
			in a future specification of Autonomous System Confederations for BGP
			-- one that would obsolete RFC 5065 -- the use of AS_CONFED_SET will
			not be specified.
			5. Security Considerations
	This document obsoletes the use of aggregation techniques that create		This document obsoletes the use of aggregation techniques that create
	AS_SETs or AS_CONFED_SETs. Obsoleting these path segment types from		AS_SETs or AS_CONFED_SETs. Obsoleting these path segment types from
	BGP and removal of the related code from implementations would		BGP and removal of the related code from implementations would
	potentially decrease the attack surface for BGP.		potentially decrease the attack surface for BGP. Deployments of new
			BGP security technologies [RFC6480] [RFC6811] [RFC8205] benefit
			greatly if AS_SET and AS_CONFED_SET are not used in BGP.
	5. IANA Considerations		6. IANA Considerations
	This document requires no IANA actions.		This document requires no IANA actions.
	6. Acknowledgements		7. Acknowledgements
	The authors would like to thank Tony Li, Randy Bush, John Scudder,		The authors would like to thank Jeffery Haas, John Heasley, Job
	Curtis Villamizar, Danny McPherson, Chris Morrow, Tom Petch, Ilya		Snijders, Jared Mauch, Jakob Heitz, Keyur Patel, Douglas Montgomery,
	Varlashkin, Douglas Montgomery, Enke Chen, Florian Weimer, Jakob		Randy Bush, Susan Hares, John Scudder, Curtis Villamizar, Danny
	Heitz, John Leslie, Keyur Patel, Paul Jakma, Rob Austein, Russ		McPherson, Chris Morrow, Tom Petch, Ilya Varlashkin, Enke Chen, Tony
			Li, Florian Weimer, John Leslie, 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, and Alvaro Retana.		Alfred Hoenes, and Alvaro Retana for comments and suggestions.
	7. References		8. References
	7.1. Normative References		8.1. 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		[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
	Border Gateway Protocol 4 (BGP-4)", RFC 4271,		Border Gateway Protocol 4 (BGP-4)", RFC 4271,
	DOI 10.17487/RFC4271, January 2006,		DOI 10.17487/RFC4271, January 2006,
	<https://www.rfc-editor.org/info/rfc4271>.		<https://www.rfc-editor.org/info/rfc4271>.
	[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous		[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
	System Confederations for BGP", RFC 5065,		System Confederations for BGP", RFC 5065,
	DOI 10.17487/RFC5065, August 2007,		DOI 10.17487/RFC5065, August 2007,
	<https://www.rfc-editor.org/info/rfc5065>.		<https://www.rfc-editor.org/info/rfc5065>.
	7.2. Informative References		8.2. Informative References
	[Analysis]		[Analysis]
	Sriram, K. and D. Montgomery, "Measurement Data on AS_SET		Hannachi, L. and K. Sriram, "Detailed analysis of AS_SETs
	and AGGREGATOR: Implications for {Prefix, Origin}		in BGP updates", NIST Robust Inter-domain Routing Project
	Validation Algorithms", SIDR WG presentation, IETF 78,		Website , October 2019,
	July 2010, <http://www.nist.gov/itl/antd/upload/		<https://www.nist.gov/sites/default/files/
	AS_SET_Aggregator_Stats.pdf>.		documents/2019/10/23/detailed-as_set-analysis.txt>.
	[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,		[IANA-SP-ASN]
	selection, and registration of an Autonomous System (AS)",		"Special-Purpose Autonomous System (AS) Numbers",
	BCP 6, RFC 1930, DOI 10.17487/RFC1930, March 1996,		<https://www.iana.org/assignments/iana-as-numbers-special-
	<https://www.rfc-editor.org/info/rfc1930>.		registry/iana-as-numbers-special-registry.xhtml>.
	[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>.
	[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>.
			[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
			Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
			February 2012, <https://www.rfc-editor.org/info/rfc6480>.
	[RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.		[RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
	Austein, "BGP Prefix Origin Validation", RFC 6811,		Austein, "BGP Prefix Origin Validation", RFC 6811,
	DOI 10.17487/RFC6811, January 2013,		DOI 10.17487/RFC6811, January 2013,
	<https://www.rfc-editor.org/info/rfc6811>.		<https://www.rfc-editor.org/info/rfc6811>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol		[RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
	skipping to change at line 254 ¶		skipping to change at page 7, line 4 ¶
	Email: warren@kumari.net		Email: warren@kumari.net
	Kotikalapudi Sriram		Kotikalapudi Sriram
	USA NIST		USA NIST
	100 Bureau Drive		100 Bureau Drive
	Gaithersburg, MD 20899		Gaithersburg, MD 20899
	US		US
	Phone: +1 301 975 3973		Phone: +1 301 975 3973
	Email: sriram.ietf@gmail.com		Email: sriram.ietf@gmail.com
			Lilia Hannachi
			USA NIST
			100 Bureau Drive
			Gaithersburg, MD 20899
			US
			Phone: +1 301 975 3259
			Email: lilia.hannachi@nist.gov
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