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Lectures notes for 2010 - KTH

Lectures notes for 2010 - KTH

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Link-State Multicast: MOSPF [5]<br />

Just add multicast to a link-state routing protocol thus OSPF ⇒ MOSPF<br />

• Use the multiprotocol facility in OSPF to carry multicast in<strong>for</strong>mation<br />

• Extended with a group-membership LSA<br />

• This LSA lists only members of a given group<br />

• Use the resulting link-state database to build delivery trees<br />

• Compute least-cost source-based trees considering metrics using Dijkstra’s algorithm<br />

• A tree is computed <strong>for</strong> each (S,G) pair with a given source (S), this is done <strong>for</strong> all S<br />

• Remember that as a link-state routing protocol that every router will know the topology of the<br />

complete network<br />

• However, it is expensive to keep store all this in<strong>for</strong>mation (and most is<br />

unnecessary)<br />

• Cache only the active (S,G) pairs<br />

• Use a data-driven approach, i.e., only computes a new tree when a multicast datagram<br />

arrives <strong>for</strong> this group<br />

Maguire Link-State Multicast: MOSPF [5] 8: 37 of 78<br />

maguire@kth.se <strong>2010</strong>.03.21 Internetworking/Internetteknik

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