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 multicast tree that connects all group members. Mobile IP is the proposed standard for IP mobility support and provides two schemes for mobile hosts to receive multicast packets, either through tunneling from the home agent (called home subscription) or by joining multicast groups in the visited foreign network (called remote subscription). The former compromises the link sharing of IP Multicast and uses sub-optimal routing, while the latter requires the foreign agent to be a multicast router and may incur frequent modifications of the multicast tree due to host mobility. This paper introduces multicast agents for IP Multicast to mobile hosts. A multicast agent is a multicast router that serves multiple (foreign) networks. A foreign agent in the service area of a multicast agent notifies the multicast agent of the multicast groups that visiting mobile hosts belong to. The multicast agent joins these multicast groups and tunnels multicast packets for these groups to the foreign agent. The foreign agent delivers multicast packets to mobile hosts using local multicast whenever possible. Simulation results show that the delay and the cost of delivery per multicast packet in our approach is close to the optimal case in remote subscription. Our approach has a lower disruption of multicast services due to mobility when groups are sparse.