Diff: rfc9774v1.txt - rfc9774.txt

	rfc9774v1.txt	rfc9774.txt

	skipping to change at line 94 ¶	skipping to change at line 94 ¶
	overlap at the origin AS	overlap at the origin AS
	B.3. Scenario 3: First one route, then another, and the AS_PATHs	B.3. Scenario 3: First one route, then another, and the AS_PATHs
	overlap at the neighbor AS	overlap at the neighbor AS
	B.4. Achieving Consistent Origin AS During Aggregation	B.4. Achieving Consistent Origin AS During Aggregation
	Appendix C. Discussion on Forwarding Loops and AS_SETs	Appendix C. Discussion on Forwarding Loops and AS_SETs
	Acknowledgements	Acknowledgements
	Authors' Addresses	Authors' Addresses

	1. Introduction	1. Introduction


	BCP 172 [RFC6472] recommends not using AS_SET [RFC4271] and	[BCP172] recommends not using AS_SET [RFC4271] and AS_CONFED_SET
	AS_CONFED_SET [RFC5065] AS_PATH path segment types in the Border	[RFC5065] AS_PATH path segment types in the Border Gateway Protocol
	Gateway Protocol (BGP). This document advances the BCP	(BGP). This document advances the BCP recommendation to a standards
	recommendation to a standards requirement in BGP; it prohibits the	requirement in BGP; it prohibits the use of the AS_SET and
	use of the AS_SET and AS_CONFED_SET types of path segments in the	AS_CONFED_SET types of path segments in the AS_PATH. The purpose is
	AS_PATH. The purpose is to simplify the design and implementation of	to simplify the design and implementation of BGP and to make the
	BGP and to make the semantics of the originator of a BGP route	semantics of the originator of a BGP route clearer. This will also
	clearer. This will also simplify the design, implementation, and	simplify the design, implementation, and deployment of various BGP
	deployment of various BGP security mechanisms. In particular, the	security mechanisms. In particular, the prohibition of AS_SETs and
	prohibition of AS_SETs and AS_CONFED_SETs removes any ambiguity about	AS_CONFED_SETs removes any ambiguity about the origin AS in RPKI-
	the origin AS in RPKI-based Route Origin Validation (RPKI-ROV)	based Route Origin Validation (RPKI-ROV) [RFC6811] [RFC6907]
	[RFC6811] [RFC6907] [RFC9319].	[RFC9319].

	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 contributing prefixes in the aggregate have traversed.	(ASes) that contributing prefixes in the aggregate have traversed.

	The AS_CONFED_SET path segment [RFC5065] in the AS_PATH attribute is	The AS_CONFED_SET path segment [RFC5065] in the AS_PATH attribute is
	created by a router that is performing route aggregation and contains	created by a router that is performing route aggregation and contains
	an unordered set of Member AS Numbers in the local confederation that	an unordered set of Member AS Numbers in the local confederation that
	contributing prefixes in the aggregate have traversed. It is very	contributing prefixes in the aggregate have traversed. It is very

	skipping to change at line 199 ¶	skipping to change at line 199 ¶
	\|	\|
	\| If an aggregate excludes at least some of the AS numbers present	\| If an aggregate excludes at least some of the AS numbers present
	\| in the AS_PATH of the routes that are aggregated as a result of	\| in the AS_PATH of the routes that are aggregated as a result of
	\| dropping the AS_SET, the aggregated route, when advertised to the	\| dropping the AS_SET, the aggregated route, when advertised to the
	\| peer, SHOULD include the ATOMIC_AGGREGATE attribute.	\| peer, SHOULD include the ATOMIC_AGGREGATE attribute.

	When BGP AS_PATH aggregation is done according to the procedures in	When BGP AS_PATH aggregation is done according to the procedures in
	[RFC4271], Section 9.2.2.2, and any resulting AS_SETs are discarded,	[RFC4271], Section 9.2.2.2, and any resulting AS_SETs are discarded,
	it is typically referred to as "brief" aggregation in	it is typically referred to as "brief" aggregation in
	implementations. Brief aggregation results in an AS_PATH that has	implementations. Brief aggregation results in an AS_PATH that has

	the property (from [RFC4271], Section 9.2.2.2):	the following property (from [RFC4271], Section 9.2.2.2):

	\| [D]etermine the longest leading sequence of tuples (as defined	\| [D]etermine the longest leading sequence of tuples (as defined
	\| above) common to all the AS_PATH attributes of the routes to be	\| above) common to all the AS_PATH attributes of the routes to be
	\| aggregated. Make this sequence the leading sequence of the	\| aggregated. Make this sequence the leading sequence of the
	\| aggregated AS_PATH attribute.	\| aggregated AS_PATH attribute.

	The ATOMIC_AGGREGATE Path Attribute is subsequently attached to the	The ATOMIC_AGGREGATE Path Attribute is subsequently attached to the
	BGP route, if AS_SETs are dropped.	BGP route, if AS_SETs are dropped.

	5.1. Issues with "Brief" AS_PATH Aggregation and RPKI-ROV	5.1. Issues with "Brief" AS_PATH Aggregation and RPKI-ROV

	skipping to change at line 303 ¶	skipping to change at line 303 ¶
	AS_CONFED_SETs are not used in BGP.	AS_CONFED_SETs are not used in BGP.

	8. IANA Considerations	8. IANA Considerations

	This document has no IANA actions.	This document has no IANA actions.

	9. References	9. References

	9.1. Normative References	9.1. Normative References


		[BCP172] Best Current Practice 172,
		<https://www.rfc-editor.org/info/bcp172>.
		At the time of writing, this BCP comprises the following:

		Kumari, W. and K. Sriram, "Recommendation for Not Using
		AS_SET and AS_CONFED_SET in BGP", BCP 172, RFC 6472,
		DOI 10.17487/RFC6472, December 2011,
		<https://www.rfc-editor.org/info/rfc6472>.

	[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>.

	[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing	[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
	(CIDR): The Internet Address Assignment and Aggregation	(CIDR): The Internet Address Assignment and Aggregation
	Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August	Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
	2006, <https://www.rfc-editor.org/info/rfc4632>.	2006, <https://www.rfc-editor.org/info/rfc4632>.

	[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>.


	[RFC6472] Kumari, W. and K. Sriram, "Recommendation for Not Using
	AS_SET and AS_CONFED_SET in BGP", BCP 172, RFC 6472,
	DOI 10.17487/RFC6472, December 2011,
	<https://www.rfc-editor.org/info/rfc6472>.

	[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet	[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
	Autonomous System (AS) Number Space", RFC 6793,	Autonomous System (AS) Number Space", RFC 6793,
	DOI 10.17487/RFC6793, December 2012,	DOI 10.17487/RFC6793, December 2012,
	<https://www.rfc-editor.org/info/rfc6793>.	<https://www.rfc-editor.org/info/rfc6793>.

	[RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.	[RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
	Patel, "Revised Error Handling for BGP UPDATE Messages",	Patel, "Revised Error Handling for BGP UPDATE Messages",
	RFC 7606, DOI 10.17487/RFC7606, August 2015,	RFC 7606, DOI 10.17487/RFC7606, August 2015,
	<https://www.rfc-editor.org/info/rfc7606>.	<https://www.rfc-editor.org/info/rfc7606>.


	skipping to change at line 518 ¶	skipping to change at line 522 ¶
	Receive R4. Aggregate 192.0.2.0/24 AS_PATH "[ 64504 64501 ]"	Receive R4. Aggregate 192.0.2.0/24 AS_PATH "[ 64504 64501 ]"

	If brief aggregation is in use, the AS_PATH is truncated to "".	If brief aggregation is in use, the AS_PATH is truncated to "".

	The resulting AS_PATH is thus not stable and depends on the presence	The resulting AS_PATH is thus not stable and depends on the presence
	of specific routes.	of specific routes.

	B.3. Scenario 3: First one route, then another, and the AS_PATHs	B.3. Scenario 3: First one route, then another, and the AS_PATHs
	overlap at the neighbor AS	overlap at the neighbor AS


	Receive R3. Aggregate 192.0.2.0/24 AS_PATH "64504 64501".	Receive R3. Aggregate 192.0.2.0/24 AS_PATH "64504 64501"

	Receive R4. Aggregate 192.0.2.0/24 AS_PATH "64504 [ 64501 64502 ]"	Receive R4. Aggregate 192.0.2.0/24 AS_PATH "64504 [ 64501 64502 ]"

	If brief aggregation is in use, the AS_PATH is truncated to "64504".	If brief aggregation is in use, the AS_PATH is truncated to "64504".

	The resulting AS_PATH is thus not stable and depends on the presence	The resulting AS_PATH is thus not stable and depends on the presence
	of specific routes.	of specific routes.

	B.4. Achieving Consistent Origin AS During Aggregation	B.4. Achieving Consistent Origin AS During Aggregation


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