Multicast routing [3]
l Networks with no
group members
pruned from tree
l Must somehow allow
tree to re-grow
l Soft-state:
– timeout – re-flood
– downstream nodes
prune again
l Explicit graft:
– downstream nodes join
tree
•  Third refinement:
•  pruning
•  need to refresh tree – soft-state
•  reverse path multicasting (RPM)