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Point to point links AND reverse path flooding

Assume we have a network of nodes connected via point to point links, and a source S sends a message that will be broadcast to all nodes using Reverse-Path-Flooding. Assume that routers do not keep track of broadcast messages they have seen earlier.

Assume also that routing tables change frequently, however, when a node changes its next-hop neighbor towards S, it is always ensured that the spanning tree used in RPF is loop-free (i.e. all nodes remain connected to the tree and there are no loops, the integrity of the tree is preserved)

Show that even with the above restrictions, it is possible that a message traverses the network and never stops (well, it will stop when its time-to-live expires, but assume messages don't have a time-to-live limit)

Solution Preview

Please see the attached files.

When a router receives a multicast packet with a given source address, it will broadcast the packet to all of its port except on the link on which the packet originally arrived, only if the packet arrived on its own link which is the at the shortest path back to the source; otherwise it simply discards the packet without forwarding it. Because the router knows that either it has already received the packet or will be receiving a copy of the packet from the sender on one of its shortest links back to the sender.

Since the network is using spanning tree protocol so that there are no loops then also it is possible that the message ...

Solution Summary

Point to point links AND reverse path flooding are shown.