[ns] Problems with multicast (BST/etc.)

[Aaron D Striegel <adstrieg@iastate.edu>]

I'm having several difficulties with the multicast portion of the ns 
code.  I am attempting to port the replication process over to C++ (which I 
have done crudely once for a different protocol) such that the replication 
process is based off of a header included in the C++ file such that I can 
avoid stateful information in the node.

I have this all working successfully for control packets so I know my 
technique does work.  However, when I am trying to do this for the data 
packets, I get an no-slot handler message.  This occurs only when the 
packets are actually arrive at a node (i.e. it works for packets that are 
produced at a given node).  This behavior is extremely weird as I would 
expect the initial arrival at the node to cause a problem with a no-slot 
classifier.

So here are my questions and perhaps someone can enlighten me:

- How does a packet actually make it to the multicast classifier, 
specifically the control classifier and the data classifier?  I can get the 
packet to the control classifier (no problem) and to the data classifier 
(source node only) so what do I need to do to get it to my custom multicast 
classifier object?  It does arrive at my classifier object as a source so 
it appears to be some sort of linkage problem upon arriving at an incoming 
interface.

- Do I need to install another agent or put on a replicator that responds 
to that group?  If so, how can I do that if I can't see the data packet in 
the first place to do anything.  Any suggestions on how to debug what/where 
things are going bad?

- Finally, is there any way that someone who is working on the multicast 
internals could contact me?  I fear this question is a bit more technical 
than your average sort of questions for the users group.  Of course, I 
would like to be proven wrong on this point but if someone could e-mail me 
so I could go into more detail on this subject/help debug my problem, that 
would be great.

--------------------------------------------
Aaron Striegel
Ph.D. Candidate, Computer Engineering
Iowa State University
http://www.public.iastate.edu/~magico