Supporting IP Multicast for mobile hosts

IP Multicast is an efficient mechanism of delivering a large amount of data to a group of members over the Internet. Link sharing is achieved by a mul ticast tree that connects all group members. Mobile IP is the proposed stan dard for IP mobility support and provides two schemes for mobile hosts to r eceive multicast packets, either through tunneling from the home agent (cal led home subscription) or by joining multicast groups in the visited foreig n network (called remote subscription). The former compromises the link sha ring of IP Multicast and uses sub-optimal routing, while the latter require s the foreign agent to be a multicast router and may incur frequent modific ations of the multicast tree due to host mobility. This paper introduces mu lticast agents for IP Multicast to mobile hosts. A multicast agent is a mul ticast router that serves multiple (foreign) networks. A foreign agent in t he service area of a multicast agent notifies the multicast agent of the mu lticast groups that visiting mobile hosts belong to. The multicast agent jo ins these multicast groups and tunnels multicast packets for these groups t o the foreign agent. The foreign agent delivers multicast packets to mobile hosts using local multicast whenever possible. Simulation results show tha t the delay and the cost of delivery per multicast packet in our approach i s close to the optimal case in remote subscription. Our approach has a lowe r disruption of multicast services due to mobility when groups are sparse.