Multicast Extensions to OSPF

Moy

network routing multicast

@misc{moy:ietf-1994,
  author={J. Moy},
  title={Multicast Extensions to {OSPF}},
  series={Request for Comments},
  number={1584},
  howpublished={{RFC} 1584},
  publisher={IETF},
  organization={Internet Engineering Task Force},
  year={1994},
  month={March},
  url={\url{http://www.ietf.org/rfc/rfc1584.txt}}
}

Multicast OSPF (MOSPF)~\cite{moy:ietf-1994} instead constructs shortest path multicast trees via link state computation. Group membership for all of a router's directly connected hosts are included in the route's link state advertisements (LSA) via an extension to the OSPF LSAs. As the LSAs propagate, all routers thus know the location of all members of all groups in addition to the standard OSPF network topology information. When a multicast source is detected, routers compute the shortest paths from that source to all members in the group using that global information, caching the results until network change triggers recomputation. The router then forwards received messages appropriately, or not, based on its position in that tree. Notably, every router thus maintains state about the combination of all sources for all groups, which can be significant.