[ns] agent/multicast

[Sencun Zhu <szhu1@ise.gmu.edu>]

Hello, all:

     Can one agent at the same time join in two multicast groups?

$node join-group $agent $group(1)
$node join-group $agent $group(2)


so that it can receive and send data to two groups at the same time.

>From the source code : agent.h, node.h , ns-agent.tcl I can not find where 
node_ is defined as instance variable for  class agent, while I noticed:
$agent set node_ ...
  

thank you.

Sencun.