[ns] generate new multicast groups dynamically

["Jian Wang" <jwangc@cs.sfu.ca>]

Dear ns users,

Given the following topology for a video on demand system:

S---R0---R1---R2---C1
         |
         |
         C2

Say if at time 0.1 client C1 asks for a video from server S, 
S will send the video data to client C1. At time 0.4 client
C2 asks for the same video from S, then R1 may serve C2 if 
it has cached the data needed. In order to realize these, 
I put every node in a multicast group so that the intermediate
routers can cache the data sent from S. If R1 is going to
serve C2, then a new multicast group needs to be created
dynamically, where R1 is working as a server to send video
data to C2. Could you give me some hints how to do that in
C++ level? Is it ok for a node to belong to multiple multicast
groups?

Thanks. Your help is really appreciated.


Jian