Efficient Multicast Routing in MANETs Using Prefix Labels

We introduce prefix ordering for efficient multicasting (POEM), the first approach to multicast routing in MANETs in which the network-wide dissemination of control information is independent of the number of groups and sources per group. POEM establishes a labeled directed acyclic graph (LDAG) rooted at an elected node in the MANET and assigns a prefix label to each node denoting its network location relative to the root of the LDAG. Routes between any two prefix labels are implicit in the labels themselves. The sources and receivers of a multicast group use a consistent hashing function to map the identifier of the group (e.g., an IP multicast address) onto the group-prefix-label. The node whose prefix label is the closest match to the group-prefix-label serves as the core of the group. As in prior receiver-initiated multicast approaches, receivers join a multicast group by sending join requests towards the group core, and multicast sources simply forward their multicast data packets towards the cores of the groups. We use simulation experiments to compare POEM with ODMRP and MAODV for different mobility scenarios with varying number of nodes, groups and receivers. The results clearly show that POEM is far more efficient than traditional multicast routing approaches, even in relatively small networks.