rfc9774v2.txt		rfc9774.txt
	skipping to change at line 80 ¶		skipping to change at line 80 ¶
	6.2. Not Advertising Aggregate Routes to Contributing ASes		6.2. Not Advertising Aggregate Routes to Contributing ASes
	6.3. Mitigating Forwarding Loops		6.3. Mitigating Forwarding Loops
	7. Security Considerations		7. Security Considerations
	8. IANA Considerations		8. IANA Considerations
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	9.2. Informative References		9.2. Informative References
	Appendix A. Example of Route Filtering for Aggregate Routes and		Appendix A. Example of Route Filtering for Aggregate Routes and
	Their Contributors		Their Contributors
	Appendix B. Examples of Consistent and Inconsistent BGP Origin AS		Appendix B. Examples of Consistent and Inconsistent BGP Origin AS
	Generated by Traditional Brief Aggregation		Generated by Brief Aggregation
	B.1. Scenario 1: First one route, then another, each with a		B.1. Scenario 1: First one route, then another, each with a
	fully disjoint AS_PATH		fully disjoint AS_PATH
	B.2. Scenario 2: First one route, then another, and the AS_PATHs		B.2. Scenario 2: First one route, then another, and the AS_PATHs
	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
	skipping to change at line 198 ¶		skipping to change at line 198 ¶
	| advertised without the AS_SET, and without forming route loops.		| advertised without the AS_SET, and without forming route loops.
	|		|
	| 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. That terminology is adopted here: In this document,
	the following property (from [RFC4271], Section 9.2.2.2):		brief aggregation refers to what is described in this section, in
			contrast to consistent brief aggregation as described in Section 5.2.
			Brief aggregation results in an AS_PATH that has 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 452 ¶		skipping to change at line 455 ¶
	AS 64505		AS 64505
	==========================		==========================
	p/22 AS_PATH "" AGGREGATOR 64505 ATOMIC_AGGREGATE		p/22 AS_PATH "" AGGREGATOR 64505 ATOMIC_AGGREGATE
	p1/24 AS_PATH "64501"		p1/24 AS_PATH "64501"
	p2/24 AS_PATH "64502"		p2/24 AS_PATH "64502"
	p3/24 AS_PATH "64503"		p3/24 AS_PATH "64503"
	p4/24 AS_PATH "64504"		p4/24 AS_PATH "64504"
	Appendix B. Examples of Consistent and Inconsistent BGP Origin AS		Appendix B. Examples of Consistent and Inconsistent BGP Origin AS
	Generated by Traditional Brief Aggregation		Generated by Brief Aggregation
	The examples below illustrate how traditional brief aggregation may		The examples below illustrate how brief aggregation may result in an
	result in an inconsistent origin AS.		inconsistent origin AS.
	AS 64500 aggregates more specific routes into 192.0.2.0/24.		AS 64500 aggregates more specific routes into 192.0.2.0/24.
	Consider the following scenarios where brief aggregation is done by		Consider the following scenarios where brief aggregation is done by
	AS 64500 and what the resultant origin ASes would be.		AS 64500 and what the resultant origin ASes would be.
	Routes:		Routes:
	R1 - 192.0.2.0/26 AS_PATH "64501"		R1 - 192.0.2.0/26 AS_PATH "64501"
	R2 - 192.0.2.64/26 AS_PATH "64502"		R2 - 192.0.2.64/26 AS_PATH "64502"
	R3 - 192.0.2.128/26 AS_PATH "64504 64502"		R3 - 192.0.2.128/26 AS_PATH "64504 64502"
	skipping to change at line 533 ¶		skipping to change at line 536 ¶
	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
	In the three scenarios above, the aggregating AS 64500 is using		In the three scenarios above, the aggregating AS 64500 is using brief
	traditional brief aggregation. This results in inconsistent origin		aggregation. This results in inconsistent origin ASes as the
	ASes as the contributing routes are learned. This motivates the		contributing routes are learned. This motivates the "consistent
	"consistent brief" BGP aggregation mentioned in Section 5.2 and		brief" BGP aggregation mentioned in Section 5.2 and discussed further
	discussed further with examples below.		with examples below.
	The trivial solution to addressing the issue is to simply discard all		The trivial solution to addressing the issue is to simply discard all
	of the ASes for the contributing routes. In simple BGP aggregation		of the ASes for the contributing routes. In simple BGP aggregation
	topologies, this is likely the correct thing to do. The AS		topologies, this is likely the correct thing to do. The AS
	originating the aggregate, 192.0.2.0/24 in this example, is likely		originating the aggregate, 192.0.2.0/24 in this example, is likely
	the resource holder for the route in question. In such a case,		the resource holder for the route in question. In such a case,
	simply originating the route to its BGP upstream neighbors in the		simply originating the route to its BGP upstream neighbors in the
	Internet with its own AS, 64500, means that a consistent ROA could be		Internet with its own AS, 64500, means that a consistent ROA could be
	registered in the RPKI for this prefix. This satisfies the need for		registered in the RPKI for this prefix. This satisfies the need for
	a consistent (unambiguous) origin AS.		a consistent (unambiguous) origin AS.
End of changes. 5 change blocks.
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