You will not be able to forward multicast with mcast policies. Basically the nature of multicast traffic is that it is not forwarded by routing devices. Multicast traffic is always seen as self traffic to layer 3 devices, and in order to forward you must have PIM dense mode enabled or PIM-SM or PIM-SSM with proper PIM or IGMP joins. This is not specific to Juniper devices, it applies to all layer 3 devices. Once you have PIM working then this is when the mcast policies would come into play to permit/deny the mcast stream.
So the question to ask with regards to your IP phone system is does the IP phone use PIM-DM, PIM-SM or PIM-SSM? If PIM-SM then this is supported on ScreenOS 5.4.0. Your IP phone will need to send IGMP joins to a multicast group and receivers would also need tp send join to their nearest router. If PIM-SSM, then that is supported in later versions of ScreenOS but not on 5GT because latest for 5GT is 5.4.0. If PIM-DM then this is not supported on ScreenOS at all.
Hope this helps.
-Richard
Message Edited by rkim on 03-17-2009 11:14 PM