Diff: rfc9350v4.txt - rfc9350.txt

	rfc9350v4.txt	rfc9350.txt

	skipping to change at line 12 ¶	skipping to change at line 12 ¶
	Internet Engineering Task Force (IETF) P. Psenak, Ed.	Internet Engineering Task Force (IETF) P. Psenak, Ed.
	Request for Comments: 9350 Cisco Systems, Inc.	Request for Comments: 9350 Cisco Systems, Inc.
	Category: Standards Track S. Hegde	Category: Standards Track S. Hegde
	ISSN: 2070-1721 Juniper Networks, Inc.	ISSN: 2070-1721 Juniper Networks, Inc.
	C. Filsfils	C. Filsfils
	Cisco Systems, Inc.	Cisco Systems, Inc.
	K. Talaulikar	K. Talaulikar
	Cisco Systems, Inc	Cisco Systems, Inc
	A. Gulko	A. Gulko
	Edward Jones	Edward Jones

	January 2023	February 2023

	IGP Flexible Algorithm	IGP Flexible Algorithm

	Abstract	Abstract

	IGP protocols historically compute the best paths over the network	IGP protocols historically compute the best paths over the network
	based on the IGP metric assigned to the links. Many network	based on the IGP metric assigned to the links. Many network
	deployments use RSVP-TE or Segment Routing - Traffic Engineering (SR-	deployments use RSVP-TE or Segment Routing - Traffic Engineering (SR-
	TE) to steer traffic over a path that is computed using different	TE) to steer traffic over a path that is computed using different
	metrics or constraints than the shortest IGP path. This document	metrics or constraints than the shortest IGP path. This document

	skipping to change at line 324 ¶	skipping to change at line 324 ¶
	Priority: value between 0 and 255 inclusive that specifies the	Priority: value between 0 and 255 inclusive that specifies the
	priority of the advertisement. Numerically greater values are	priority of the advertisement. Numerically greater values are
	preferred. Usage of the priority is described in Section 5.3.	preferred. Usage of the priority is described in Section 5.3.

	Sub-TLVs: optional sub-TLVs.	Sub-TLVs: optional sub-TLVs.

	The IS-IS FAD sub-TLV MAY be advertised in a Label Switched Path	The IS-IS FAD sub-TLV MAY be advertised in a Label Switched Path
	(LSP) of any number. The IS-IS router MAY advertise more than one	(LSP) of any number. The IS-IS router MAY advertise more than one
	IS-IS FAD sub-TLV for a given Flexible Algorithm (see Section 6).	IS-IS FAD sub-TLV for a given Flexible Algorithm (see Section 6).


	The IS-IS FAD sub-TLV has an area scope. The Router Capability TLV	The IS-IS FAD sub-TLV has an area/level scope. The Router Capability
	in which the FAD sub-TLV is present MUST have the S bit clear.	TLV in which the FAD sub-TLV is present MUST have the S bit clear.

	An IS-IS L1/L2 router MAY be configured to regenerate the winning FAD	An IS-IS L1/L2 router MAY be configured to regenerate the winning FAD
	from level 2, without any modification to it, to the level 1 area.	from level 2, without any modification to it, to the level 1 area.
	The regeneration of the FAD sub-TLV from level 2 to level 1 is	The regeneration of the FAD sub-TLV from level 2 to level 1 is
	determined by the L1/L2 router, not by the originator of the FAD	determined by the L1/L2 router, not by the originator of the FAD
	advertisement in level 2. In such a case, the regenerated FAD sub-	advertisement in level 2. In such a case, the regenerated FAD sub-
	TLV will be advertised in the level 1 Router Capability TLV	TLV will be advertised in the level 1 Router Capability TLV
	originated by the L1/L2 router.	originated by the L1/L2 router.

	An L1/L2 router MUST NOT regenerate any FAD sub-TLV from level 1 to	An L1/L2 router MUST NOT regenerate any FAD sub-TLV from level 1 to

	skipping to change at line 957 ¶	skipping to change at line 955 ¶
	ignored.	ignored.

	If a prefix is advertised with a Flex-Algorithm prefix metric larger	If a prefix is advertised with a Flex-Algorithm prefix metric larger
	than MAX_PATH_METRIC, as defined in [RFC5305], this prefix MUST NOT	than MAX_PATH_METRIC, as defined in [RFC5305], this prefix MUST NOT
	be considered during the Flexible Algorithm computation.	be considered during the Flexible Algorithm computation.

	The usage of the Flex-Algorithm prefix metric is described in	The usage of the Flex-Algorithm prefix metric is described in
	Section 13.	Section 13.

	The IS-IS FAPM sub-TLV MUST NOT be advertised as a sub-TLV of the IS-	The IS-IS FAPM sub-TLV MUST NOT be advertised as a sub-TLV of the IS-

	IS SRv6 Locator TLV [RFCYYY1]. The IS-IS SRv6 Locator TLV includes	IS SRv6 Locator TLV [RFC9352]. The IS-IS SRv6 Locator TLV includes
	the Algorithm and Metric fields, which MUST be used instead. If the	the Algorithm and Metric fields, which MUST be used instead. If the
	FAPM sub-TLV is present as a sub-TLV of the IS-IS SRv6 Locator TLV in	FAPM sub-TLV is present as a sub-TLV of the IS-IS SRv6 Locator TLV in
	the received LSP, such FAPM sub-TLV MUST be ignored.	the received LSP, such FAPM sub-TLV MUST be ignored.

	9. OSPF Flexible Algorithm Prefix Metric Sub-TLV	9. OSPF Flexible Algorithm Prefix Metric Sub-TLV

	The OSPF Flexible Algorithm Prefix Metric (FAPM) sub-TLV supports the	The OSPF Flexible Algorithm Prefix Metric (FAPM) sub-TLV supports the
	advertisement of a Flex-Algorithm-specific prefix metric associated	advertisement of a Flex-Algorithm-specific prefix metric associated
	with a given prefix advertisement.	with a given prefix advertisement.


	skipping to change at line 1514 ¶	skipping to change at line 1512 ¶
	unsigned 32-bit variable. In such scenarios, the value MUST be	unsigned 32-bit variable. In such scenarios, the value MUST be
	considered to be of value 0xFFFFFFFF during the computation and	considered to be of value 0xFFFFFFFF during the computation and
	advertised as such.	advertised as such.

	The FAPM MUST NOT be advertised with IS-IS L1 or L2 intra-area,	The FAPM MUST NOT be advertised with IS-IS L1 or L2 intra-area,
	OSPFv2 intra-area, or OSPFv3 intra-area routes. If the FAPM is	OSPFv2 intra-area, or OSPFv3 intra-area routes. If the FAPM is
	advertised for these route-types, it MUST be ignored during the	advertised for these route-types, it MUST be ignored during the
	prefix reachability calculation.	prefix reachability calculation.

	The M-flag in the FAD is not applicable to prefixes advertised as	The M-flag in the FAD is not applicable to prefixes advertised as

	SRv6 locators. The IS-IS SRv6 Locator TLV [RFCYYY1] includes the	SRv6 locators. The IS-IS SRv6 Locator TLV [RFC9352] includes the
	Algorithm and Metric fields. When the SRv6 Locator is advertised	Algorithm and Metric fields. When the SRv6 Locator is advertised
	between areas or domains, the Metric field in the Locator TLV of IS-	between areas or domains, the Metric field in the Locator TLV of IS-
	IS MUST be used irrespective of the M-flag in the FAD advertisement.	IS MUST be used irrespective of the M-flag in the FAD advertisement.

	OSPF external and NSSA external prefix advertisements MAY include a	OSPF external and NSSA external prefix advertisements MAY include a
	non-zero forwarding address in the prefix advertisements in the base	non-zero forwarding address in the prefix advertisements in the base
	protocol. In such a scenario, the Flex-Algorithm-specific	protocol. In such a scenario, the Flex-Algorithm-specific
	reachability of the external prefix is determined by Flex-Algorithm-	reachability of the external prefix is determined by Flex-Algorithm-
	specific reachability of the forwarding address.	specific reachability of the forwarding address.


	skipping to change at line 1596 ¶	skipping to change at line 1594 ¶
	14.2. SRv6 Forwarding for Flex-Algorithm	14.2. SRv6 Forwarding for Flex-Algorithm

	This section describes how Flex-Algorithm paths are used with SRv6	This section describes how Flex-Algorithm paths are used with SRv6
	forwarding.	forwarding.

	In SRv6, a node is provisioned with a (topology, algorithm) specific	In SRv6, a node is provisioned with a (topology, algorithm) specific
	locator for each of the topology/algorithm pairs supported by that	locator for each of the topology/algorithm pairs supported by that
	node. Each locator is an aggregate prefix for all SIDs provisioned	node. Each locator is an aggregate prefix for all SIDs provisioned
	on that node that have the matching topology/algorithm.	on that node that have the matching topology/algorithm.


	The SRv6 locator advertisement in IS-IS [RFCYYY1] includes the Multi-	The SRv6 locator advertisement in IS-IS [RFC9352] includes the Multi-
	Topology Identifier (MTID) value that associates the locator with a	Topology Identifier (MTID) value that associates the locator with a
	specific topology. SRv6 locator advertisements also include an	specific topology. SRv6 locator advertisements also include an
	algorithm value that explicitly associates the locator with a	algorithm value that explicitly associates the locator with a
	specific algorithm. When the algorithm value advertised with a	specific algorithm. When the algorithm value advertised with a
	locator represents a Flex-Algorithm, the paths to the locator prefix	locator represents a Flex-Algorithm, the paths to the locator prefix
	MUST be calculated using the specified Flex-Algorithm in the	MUST be calculated using the specified Flex-Algorithm in the
	associated topology.	associated topology.

	Forwarding entries for the locator prefixes advertised in IS-IS MUST	Forwarding entries for the locator prefixes advertised in IS-IS MUST
	be installed in the forwarding plane of the receiving SRv6-capable	be installed in the forwarding plane of the receiving SRv6-capable

	skipping to change at line 1957 ¶	skipping to change at line 1955 ¶
	+=======+=========================================+==============+	+=======+=========================================+==============+
	\| 26 \| Flexible Algorithm Prefix Metric (FAPM) \| RFC 9350, \|	\| 26 \| Flexible Algorithm Prefix Metric (FAPM) \| RFC 9350, \|
	\| \| \| Section 9 \|	\| \| \| Section 9 \|
	+-------+-----------------------------------------+--------------+	+-------+-----------------------------------------+--------------+
	\| 33 \| OSPF Flexible Algorithm ASBR Metric \| RFC 9350, \|	\| 33 \| OSPF Flexible Algorithm ASBR Metric \| RFC 9350, \|
	\| \| \| Section 10.2 \|	\| \| \| Section 10.2 \|
	+-------+-----------------------------------------+--------------+	+-------+-----------------------------------------+--------------+

	Table 9: OSPFv3 Extended-LSA Sub-TLVs Registry	Table 9: OSPFv3 Extended-LSA Sub-TLVs Registry


	For both of these sub-TLVs, the column "L2BM" in the registry is set
	to "X", meaning "sub-TLV is not a Router Link sub-TLV; it MUST NOT
	appear in L2 Bundle Member sub-TLV".

	18.4.4. OSPF Flex-Algorithm Prefix Metric Bits Registry	18.4.4. OSPF Flex-Algorithm Prefix Metric Bits Registry

	IANA has created the "OSPF Flex-Algorithm Prefix Metric Bits"	IANA has created the "OSPF Flex-Algorithm Prefix Metric Bits"
	registry under the "Open Shortest Path First (OSPF) Parameters"	registry under the "Open Shortest Path First (OSPF) Parameters"
	registry. The registration procedure is "IETF Review". Bits 1-7 are	registry. The registration procedure is "IETF Review". Bits 1-7 are
	unassigned, and the initial value has been assigned as follows.	unassigned, and the initial value has been assigned as follows.

	+============+=======================+=====================+	+============+=======================+=====================+
	\| Bit Number \| Description \| Reference \|	\| Bit Number \| Description \| Reference \|
	+============+=======================+=====================+	+============+=======================+=====================+

	skipping to change at line 2180 ¶	skipping to change at line 2174 ¶
	[RFC8919] Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and	[RFC8919] Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
	J. Drake, "IS-IS Application-Specific Link Attributes",	J. Drake, "IS-IS Application-Specific Link Attributes",
	RFC 8919, DOI 10.17487/RFC8919, October 2020,	RFC 8919, DOI 10.17487/RFC8919, October 2020,
	<https://www.rfc-editor.org/info/rfc8919>.	<https://www.rfc-editor.org/info/rfc8919>.

	[RFC8920] Psenak, P., Ed., Ginsberg, L., Henderickx, W., Tantsura,	[RFC8920] Psenak, P., Ed., Ginsberg, L., Henderickx, W., Tantsura,
	J., and J. Drake, "OSPF Application-Specific Link	J., and J. Drake, "OSPF Application-Specific Link
	Attributes", RFC 8920, DOI 10.17487/RFC8920, October 2020,	Attributes", RFC 8920, DOI 10.17487/RFC8920, October 2020,
	<https://www.rfc-editor.org/info/rfc8920>.	<https://www.rfc-editor.org/info/rfc8920>.


	[RFCYYY1] Psenak, P., Ed., Filsfils, C., Bashandy, A., Decraene, B.,	[RFC9352] Psenak, P., Ed., Filsfils, C., Bashandy, A., Decraene, B.,
	and Z. Hu, "IS-IS Extension to Support Segment Routing	and Z. Hu, "IS-IS Extensions to Support Segment Routing
	over the IPv6 Data Plane", RFC YYY1, DOI 10.17487/RFCYYY1,	over the IPv6 Data Plane", RFC 9352, DOI 10.17487/RFC9352,
	January 2023, <https://www.rfc-editor.org/info/rfcYYY1>.	February 2023, <https://www.rfc-editor.org/info/rfc9352>.

	19.2. Informative References	19.2. Informative References

	[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,	[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
	DOI 10.17487/RFC2328, April 1998,	DOI 10.17487/RFC2328, April 1998,
	<https://www.rfc-editor.org/info/rfc2328>.	<https://www.rfc-editor.org/info/rfc2328>.

	[RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",	[RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
	RFC 3101, DOI 10.17487/RFC3101, January 2003,	RFC 3101, DOI 10.17487/RFC3101, January 2003,
	<https://www.rfc-editor.org/info/rfc3101>.	<https://www.rfc-editor.org/info/rfc3101>.

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