If it's not added to your threads then I guess there are no answers.
I can give you a few links to peruse, but basically questions like these should be in /networking its way too technical.
Search this loc for info on PIM-SM and multicast references (huge):
http://citeseer.nj.nec.com/cs,
IP Multicast Links:
http://www.cs.uoregon.edu/~kurtw/multicast/, Multicast over TCP/IP HOWTO
:
http://www.yolinux.com/HOWTO/Multicast-HOWTO.html, IETF's on IP Multicast:
http://www-lor.int-evry.fr/~pascal/Mcast/drafts.htm, and maybe some from the GateDaemon Configuration Guide under 6.3.2:
http://netstats.ucar.edu/gated-4-0-3/config_guide/
You can also try to find RFC's but I don't know if you're that masochistic :-]
HTH.