New approach for mobile multicast based on SSM

The issue for mobile multicast is classified as two trends. One is route optimization and the other is how fast the multicast routing tree can be reconstructed. In the case of reconstructing the multicast tree, the FA must join the multicast group whenever the attachment point is changed. This mechanism has the advantage of route optimization for transmitting multicast data. However, the tree reconstruction may have occurred whenever the mobile host moves. Its overhead may be increased rapidly. In order to service multicast, the other way is the use of tunneling without tree reconstruction. Because the HA (home agent) is already being subscribed in the multicast session, the multicast datagram is transmitted to the HA. The HA tunnels it to the current FA (foreign agent), to which the mobile host is attached. When this mechanism is applied, the tree reconstruction is not needed. However, the path from the HA to FA may not be optimized. The longer the path distance is, the more the packet delay may increase. If the FA does not support IGMP, a more serious problem is caused. As stated above, the two mechanisms may not be implemented easily on the current network. We propose a mobile multicast mechanism based on SSM (source-specific multicast), which is proposed in order to support one-to-many transmission efficiently. However, automatic tunneling is used instead of the source-based tree. The key feature of this mechanism is to remove the overload caused by tree reconstruction and to optimize the multicast path simultaneously when the handoff occurred.