Internet Assigned Numbers Authority • Domains • Protocols • Numbers • About Interior Gateway Protocol (IGP) Parameters Created 2017-12-18 Last Updated 2026-07-10 Available Formats [IMG] XML [IMG] HTML [IMG] Plain text Registries Included Below • IGP Algorithm Types • IGP MSD-Types • Link Attribute Application Identifiers • IGP Metric-Type • IGP Flexible Algorithm Definition Flags • Path Computation Element (PCE) Capability Flags • PCE Discovery (PCED) Sub-TLV Type Indicators • IGP Algorithm Type For Computing Flooding Topology • IGP Flex-Algorithm Path Computation Rules IGP Algorithm Types Registration Procedure(s) Standards Action Reference [RFC8665] Available Formats [IMG] CSV Value Description Reference Shortest Path First (SPF) algorithm based on link metric. This is the standard shortest path algorithm as computed by the 0 IGP protocol. Consistent with the deployed practice for link-state protocols, Algorithm 0 permits any node to overwrite [RFC8665] the SPF path with a different path based on its local policy. Strict Shortest Path First (SPF) algorithm based on link metric. The algorithm is identical to Algorithm 0 but Algorithm 1 1 requires that all nodes along the path will honor the SPF routing decision. Local policy at the node claiming support [RFC8665] for Algorithm 1 MUST NOT alter the SPF paths computed by Algorithm 1. 2-127 Unassigned 128-255 Flexible Algorithms [RFC9350, Section 4] IGP MSD-Types Registration Procedure(s) Expert Review Expert(s) Uma Chunduri, Jeff Tantsura Reference [RFC8491][RFC9702] Note When this registry is modified, the YANG module "iana-msd-type" must be updated as defined in [RFC9702]. Available Formats [IMG] CSV Value Name Data Plane Reference 0 Reserved [RFC8491] 1 Base MPLS Imposition MSD MPLS [RFC8491] 2 ERLD-MSD MPLS [RFC9088] 3 Readable Label Depth MPLS [RFC9789] 4-40 Unassigned 41 SRH Max SL SRv6 [RFC9352] 42 SRH Max End Pop SRv6 [RFC9352] 43 Unassigned 44 SRH Max H.encaps SRv6 [RFC9352] 45 SRH Max End D SRv6 [RFC9352] 46-250 Unassigned 251-254 Experimental Use [RFC8491] 255 Reserved [RFC8491] Link Attribute Application Identifiers Registration Procedure(s) Expert Review Expert(s) Les Ginsberg, Chris Hopps Reference [RFC9479] Available Formats [IMG] CSV Bit Name Reference 0 RSVP-TE (R-bit) [RFC9479] 1 Segment Routing Policy (S-bit) [RFC9479] 2 Loop-Free Alternate (F-bit) [RFC9479] 3 Flexible Algorithm (X-bit) [RFC9350, Section 12] 4-63 Unassigned IGP Metric-Type Reference [RFC9350][RFC9843] Available Formats [IMG] CSV Range Registration Procedures 0-127 Standards Action 128-255 User-Defined Metric Type Description Reference Allowed in Generic-Metric 0 IGP Metric [RFC9350, Section 5.1] No 1 Min Unidirectional Link Delay as defined in [RFC8570, Section 4.2] and [RFC7471, Section 4.2] [RFC9350, Section 5.1] No 2 Traffic Engineering Default Metric as defined in [RFC5305, Section 3.7] and Traffic [RFC9350, Section 5.1] No Engineering Metric as defined in [RFC3630, Section 2.5.5] 3 Bandwidth Metric [RFC9843] Yes 4-127 Unassigned 128-255 Reserved for User-Defined Metric [RFC9843] Yes IGP Flexible Algorithm Definition Flags Registration Procedure(s) Standards Action Reference [RFC9350] Available Formats [IMG] CSV Bit Name Reference 0 Prefix Metric Flag (M-flag) [RFC9350, Sections 6.4 and 7.4] Path Computation Element (PCE) Capability Flags Registration Procedure(s) IETF Review Reference [RFC9353] Available Formats [IMG] CSV Bit Capability Description Reference 0 Path computation with GMPLS link constraints [RFC5088] 1 Bidirectional path computation [RFC5088] 2 Diverse path computation [RFC5088] 3 Load-balanced path computation [RFC5088] 4 Synchronized paths computation [RFC5088] 5 Support for multiple objective functions [RFC5088] 6 Support for additive path constraints (max hop count, etc.) [RFC5088] 7 Support for request prioritization [RFC5088] 8 Support for multiple requests per message [RFC5088] 9 Global Concurrent Optimization (GCO) [RFC5557] 10 P2MP path computation [RFC8306] 11 Active stateful PCE capability [RFC8231] 12 Passive stateful PCE capability [RFC8231] 13 Active Stateful PCE with P2MP [RFC8623] 14 Passive Stateful PCE with P2MP [RFC8623] 15 Stateful PCE Initiation with P2MP [RFC8623] 16 FlowSpec [RFC9168] 17 TCP-AO Support [RFC9353] 18 PCEP over TLS support [RFC9353] 19-31 Unassigned PCE Discovery (PCED) Sub-TLV Type Indicators Registration Procedure(s) Standards Action Reference [RFC9353] Available Formats [IMG] CSV Value Description Reference 0 Reserved [RFC9353][RFC5088] 1 PCE-ADDRESS [RFC9353][RFC5088] 2 PATH-SCOPE [RFC9353][RFC5088] 3 PCE-DOMAIN [RFC9353][RFC5088] 4 NEIG-PCE-DOMAIN [RFC9353][RFC5088] 5 PCE-CAP-FLAGS [RFC9353][RFC5088] 6 KEY-ID [RFC9353] 7 KEY-CHAIN-NAME [RFC9353] 8-65535 Unassigned IGP Algorithm Type For Computing Flooding Topology Registration Procedure(s) Expert Review Expert(s) Peter Psenak, Tony Li Reference [RFC9667] Available Formats [IMG] CSV Value Description Reference 0 Reserved for centralized mode [RFC9667] 1 Modified MANET Reduction [draft-ietf-lsr-distoptflood-13] 2-127 Unassigned 128-254 Reserved for Private Use [RFC9667] 255 Reserved [RFC9667] IGP Flex-Algorithm Path Computation Rules Registration Procedure(s) Expert Review Expert(s) Peter Psenak, Shraddha Hegde Reference [RFC9917] Available Formats [IMG] CSV Sequence Number Description Reference Check if any exclude Administrative Group rule is part of the Flex-Algorithm Definition. If such exclude rule 1 exists, check if any color that is part of the exclude rule is also set on the link. If such a color is set, the [RFC9350, Section 13] link MUST be pruned from the computation. Check if any exclude SRLG rule is part of the Flex-Algorithm Definition. If such exclude rule exists, check if 2 the link is part of any SRLG that is also part of the SRLG exclude rule. If the link is part of such SRLG, the [RFC9350, Section 13] link MUST be pruned from the computation. Check if any include-any Administrative Group rule is part of the Flex-Algorithm Definition. If such include-any 3 rule exists, check if any color that is part of the include-any rule is also set on the link. If no such color [RFC9350, Section 13] is set, the link MUST be pruned from the computation. Check if any include-all Administrative Group rule is part of the Flex-Algorithm Definition. If such include-all 4 rule exists, check if all colors that are part of the include-all rule are also set on the link. If all such [RFC9350, Section 13] colors are not set on the link, the link MUST be pruned from the computation. If the Flex-Algorithm Definition uses something other than the IGP metric (Section 5 of [RFC9350]), and such 5 metric is not advertised for the particular link in a topology for which the computation is done, such link MUST [RFC9350, Section 13] be pruned from the computation. A metric of value 0 MUST NOT be assumed in such a case. Check if any exclude FAEMB rule is part of the Flex-Algorithm definition. If such exclude rule exists and the 6 link has Maximum Link Bandwidth advertised, check if the link bandwidth satisfies the FAEMB rule. If the link [RFC9843, Section 6] does not satisfy the FAEMB rule, the link MUST be pruned from the Flex-Algorithm computation. Check if any exclude FAEMD rule is part of the Flex-Algorithm definition. If such exclude rule exists and the 7 link has Min Unidirectional link delay advertised, check if the link delay satisfies the FAEMD rule. If the link [RFC9843, Section 6] does not satisfy the FAEMD rule, the link MUST be pruned from the Flex-Algorithm computation. Check if any exclude reverse Admin Group rule is part of the Flex-Algorithm definition. If such exclude rule 8 exists, check if any Admin Group that is part of the exclude rule is also set on the link in the reverse [RFC9917, Section 11] direction. If such Admin Group is set on the link in the reverse direction, the link MUST be pruned from the computation. Check if any include-any reverse Admin Group rule is part of the Flex-Algorithm definition. If such include-any 9 rule exists, check if any Admin Group that is part of the include-any rule is also set on the link in the [RFC9917, Section 11] reverse direction. If no such Admin Group is set on the link in the reverse direction, the link MUST be pruned from the computation. Check if any include-all reverse Admin Group rule is part of the Flex-Algorithm definition. If such include-all 10 rule exists, check if all Admin Groups that are part of the include-all rule are also set on the link in the [RFC9917, Section 11] reverse direction. If all such Admin Groups are not set on the link in the reverse direction, the link MUST be pruned from the computation. Licensing Terms