H-bit Support for OSPFv2

OSPFv3 defines an option bit for router-LSAs known as the R-bit in RFC5340. If the R-bit is clear, an OSPFv3 router can participate in OSPF topology flooding, however it will not be used as a transit router. In such cases, other routers in the OSPFv3 routing domain only install routes to allow local traffic delivery. This document defines the H-bit functionality to prevent other OSPFv2 routers from using the router for transit traffic in OSPFv2 routing domains as described in RFC 2328. This document updates RFC 2328.