YANG Data Model for OSPFv3 Extended Link State Advertisements (LSAs)
Extracted elements (21)
The module augments RFC 9129 rather than defining a standalone model, following the NMDA architecture (RFC 8342). This layered augmentation approach allows the base OSPF model to remain independent while Extended LSA support is added as a composable extension.
The YANG module is applicable only when the control-plane-protocol type is 'ospf:ospfv3', enforced by YANG 'when' conditions on all augmentations. This prevents the Extended LSA schema from being applied to OSPFv2 instances.
When extended-lsa-support is disabled, OSPFv3 Extended LSAs may still be advertised in Extended LSA Sparse Mode to support incrementally deployed features, as described in Section 6.2 of RFC 8362. This allows coexistence during phased deployments.
For regular OSPFv3 areas (non-stub, non-NSSA), disabling AreaExtendedLSASupport at the area level is prohibited when ExtendedLSASupport is enabled at the instance level, enforced via a YANG 'must' constraint.
OSPFv3 prefix options are modeled as YANG identities based on 'ospfv3-e-prefix-option': nu-bit (exclude from IPv6 unicast), la-bit (prefix is router interface address), p-bit (NSSA translation trigger), dn-bit (L3VPN prefix marker), and n-bit (host address identifying advertising router).
The 'e-bit' identity under 'ospfv3-e-external-prefix-option' distinguishes Type 2 external metrics (set, metric larger than any intra-AS path) from Type 1 external metrics (clear, same units as interface costs in Router-LSAs).
The E-Inter-Area-Router-LSA container includes a list of inter-router-tlv entries, each carrying LSA options, metric, destination-router-id (router-id), and sub-TLVs.
The E-Intra-Area-Prefix-LSA container includes referenced-ls-type (uint16), referenced-link-state-id (uint32), referenced-adv-router (router-id), and a list of intra-prefix-tlv entries carrying metric, prefix, prefix-options, and sub-TLVs.
The E-Link-LSA container (for link-scope LSAs) includes router priority (uint8), LSA options, and a list of TLVs: intra-prefix-tlv, ipv6-link-local-addr-tlv, ipv4-link-local-addr-tlv, and unknown-tlv for forward compatibility.
The E-Network-LSA container includes LSA options and a list of attached-router-tlv entries, where each entry contains a leaf-list of adjacent neighbor Router IDs.
The E-Router-LSA container includes router LSA bits, LSA options, and a list of link-tlv entries. Each link-tlv carries interface-id (uint32), neighbor-interface-id (uint32), neighbor-router-id, link type, metric, and extensible sub-TLVs.
The 'extended-lsa-support' boolean leaf at the area level inherits from the instance level if unspecified. For regular areas (where AS-scoped LSAs are flooded), disabling area-level Extended LSA support is prohibited when instance-level support is enabled, because E-AS-External-LSAs flood into all regular areas.
The external-prefix-tlv grouping is shared by E-AS-External-LSA and E-NSSA-LSA. It carries external prefix flags (E-bit for Type 1/2 metric), metric, prefix, prefix-options, and sub-TLVs: ipv6-fwd-addr-sub-tlv, ipv4-fwd-addr-sub-tlv, route-tag-sub-tlv, and unknown-sub-tlv.
The module defines YANG identities for eight OSPFv3 Extended LSA types: E-Router-LSA (0xA021), E-Network-LSA (0xA022), E-Inter-Area-Prefix-LSA (0xA023), E-Inter-Area-Router-LSA (0xA024), E-AS-External-LSA (0xC025), E-NSSA-LSA (0xA027), E-Link-LSA (0x8028), and E-Intra-Area-Prefix-LSA (0xA029).
The YANG module 'ietf-ospfv3-extended-lsa' augments RFC 9129 (IETF OSPF YANG model) to add configuration and operational state for OSPFv3 Extended LSAs as defined in RFC 8362. It provides global and area-level configuration, plus LSDB operational state for link-scope, area-scope, and AS-scope Extended LSAs.
Unknown TLVs and sub-TLVs are modeled using the 'ospf:tlv' grouping with type (uint16), length (uint16), and value (yang:hex-string) fields, providing forward compatibility for future TLV extensions.
IANA registered the URI 'urn:ietf:params:xml:ns:yang:ietf-ospfv3-extended-lsa' in the IETF XML Registry (RFC 3688) as an XML namespace for this YANG module.
IANA registered the YANG module 'ietf-ospfv3-extended-lsa' in the YANG Module Names registry (RFC 6020) with namespace 'urn:ietf:params:xml:ns:yang:ietf-ospfv3-extended-lsa', prefix 'ospfv3-e-lsa', and reference RFC 9587.
NETCONF access must use SSH (RFC 6242) as the mandatory-to-implement secure transport; RESTCONF must use HTTPS with TLS (RFC 8446). NACM (RFC 8341) provides access control for NETCONF/RESTCONF operations and content.
Read access to LSDB operational state nodes exposes detailed network topology, including information from other routers. This may facilitate attacks or expose sensitive topology data that operators consider confidential. NACM (RFC 8341) should be used to restrict access.
Write access to 'extended-lsa-support' at instance or area level can cause a Denial-of-Service attack: toggling this setting causes OSPFv3 routers to use incompatible LSA types (Extended vs Legacy), resulting in incomplete reachability and possible routing domain partitioning.