It is useful for routers in an OSPFv2 or OSPFv3 routing domain to
know the capabilities of their neighbors and other routers in the
routing domain. This document proposes extensions to OSPFv2 and
OSPFv3 for advertising optional router capabilities. The Router
Information (RI) Link State Advertisement (LSA) is defined for this
purpose. In OSPFv2, the RI LSA will be implemented with an Opaque
LSA type ID. In OSPFv3, the RI LSA will be implemented with a unique
LSA type function code. In both protocols, the RI LSA can be
advertised at any of the defined flooding scopes (link, area, or
autonomous system (AS)). This document obsoletes RFC 4970 by
providing a revised specification that includes support for
advertisement of multiple instances of the RI LSA and a TLV for
functional capabilities.