The current video conference applications assume that a fixed average bandwidth is uniformly present throughout the network. Consequently, sources adjust their transmission rate to match the lowest bandwidth capacity, even though high bandwidth connectivity might be available to many of the participants. This paper proposes a new transmission system where source can selectively forward subset of layers at constrained network link. Under this transmission system, each user can receive the good quality video signal that the network can deliver. The selective forwarding is carried out using multiple IP Multicast groups where each source specifies the TTL scope of the groups. Sources find the optimal TTL scope of IP Multicast group with the feedback messages from receivers. There is TTL scope control algorithm which finds the optimal TTL scope. A prototype of the new transmission system is implemented in NV video conference application. It proves that the new transmission system works well.
