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Multicast Routing in Datagram Internetworks and Extended LANs

Steve Deering and David R. Cheriton, Stanford Univ.

One-line summary: Extensions and refinements to distance-vector and link-state/OSPF routing to support efficient multicast tree creation and maintenance in wide area internetworks. Main tradeoff is low delay (for joining or delivery) vs. increased cost in bandwidth or router state. Distance-vector routing seems to scale better.

Overview/Main Points

  • Hierarchical mcast routing: if a host or superdomain router attached to a subdomain sends mcast packet addressed to G into the subdomain, packet is delivered to all hosts in G plus all other superdomain routers attached to the subdomain.


    Extends existing routing algorithms, by successive optimizations, to handle multicast routing reasonably efficiently. Delay vs. cost tradeoffs are well illustrated, as is separation of logical (mcast group) from physical addressing.


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