[ns] How to extract the newly active outgoing interface of a multicast router?

[Ellen Yuan <eyuan@usa.net>]

Hi, ns users,

I want to do some simulation and research on multicast.

When a node is just joining a group, it will send a join message to the 
nearest on-tree router.  After the member joining is successful, 
corresponding to this join or graft message, how can I extract the 
incoming interface (iif) at this branching router? Then, how can I 
translate this iif to an appropriate outgoing interface (oif) at the 
branching router corresponding to the upstream data packets? Because the 
data packets and the join or leave messages transmit on opposite 
directions, the links in the network are all configured as duplex links.

I want to do some packet header modification at the replicator at the 
branching router for the newly grafting outgoing links.

It seems that Centralized Multicast protocol (PIM-SM) implemented in ns 
does not support join or leave message simulation, it only will do 
multicast routing computation. So if I use CtrlMcast, what can I do with 
the above objective? And if I use DM (Dense-Mode multicast) in ns, what 
can I do?

I have read Chapter 5 and Chapter 24 of ns Manual. And I find that the 
multicast protocol code are written in both C++ and OTcl. I am not 
familiar with both C++ and OTcl. So I don't know how to modify these C++ 
and OTcl codes.

Any help and suggestion will be much appreciated.

Best regards,

Ellen

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