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

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

I managed to fix the classifier problem (removed a bit of unnecessary code 
making the dest address = the node, hence explaining the classifier 
error).  However, I am now experiencing a new, much more difficult error as 
the copy mechanism for the packet does not appear to work.

if(pOutgoingLink != NULL)
{
   pOutgoingLink->recv(pPacket->copy());
}

However, although my packet makes it to the next node appropriately, it has 
lost all semblance of a destination address or source address (always 
-1).  Plus, the original pPacket object appears to get corrupted as well 
due to this code.  This is the exact same code that I have for the control 
tree replication which works 100% correct.  In fact, I just cut and paste 
the code over to remove any changes that I made.  Anyone have any 
experience working with the copy() function of the Packet object?  This 
should work for all practical purposes as I've used this before and it uses 
roughly the same principle as the replicator objects for multicast.

If anyone could contact me that has done similar work or actually wrote the 
multicast code for ns, that would be great.  Thanks

Aaron

At 05:57 PM 5/8/2001 -0500, you wrote:
>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