How to attach a replicator?

[Daniel Friedman <danielf@isr.umd.edu>]

How do I attach a replicator to..
1) an agent in a node, and
2) a node with no explicitly-attached agents?

Then, ..
3) Once I achieve #2, how do I populate the slot_ table as I like within
   Tcl?
4) For at least #1 and #2, does it make a difference if I enable
   multicasting in the simulator?  Or, must I enable it?

4) My understanding is that ns doesn't allow parallel links.  Once I
   achieve #1, can I have a link from the node 1's agent to node 2,
   and also a link from the replicator in node 1 [attached to node 1's
   agent] to node 2?  

Thank you,

--dan