Now a days I am reading IP Sec. I came to know a fact that crypto engine doesn't recoganize the multicast packets. This is the reason the multicast packets never forwarded over Ip Sec tunnels. Still to know about the fact how the protocol communication will possible over IP Sec. But I get a answer of forwarding multicast stram over IP Sec is possible only with the help of GRE. So if you are enabling the multicast services over ipsec then use GRE in the model, otherwise problem will be there.