Cored-based tree with forwarding regions (CBT-FR); a protocol for reliablemulticasting in mobile ad hoc networks

In this paper we propose a new protocol for reliable multicast in a Multiho p mobile radio network. The protocol is reliable, i.e.. it guarantees messa ge delivery to all multicast nodes even when the topology of the network ch anges during multicasting. The proposed protocol uses a core-based shared t ree. The multicast tree may get fragmented due to node movements. The notio n of a forwarding region is introduced which is used to glue together fragm ents of multicast trees. The gluing process involves flooding the forwardin g region of only those nodes that witness topology change due to node mobil ity. Delivery of multicast messages to mobile nodes is expedited through (i ) pushing the message by witness nodes in their forwarding regions and (ii) pulling messages by a mobile node during (re)joining process. Hence, the p rotocol conserves network bandwidth by using a combination of the push-pull approach and by restricting flooding only to the essential parts of the ne twork that are affected by topology change. We develop a theoretical model to compute the probability of packet loss (a s a function of the mobility rate) for our proposed scheme compared to the the core-based tree protocol (CBT); we also evaluate the effectiveness of f orwarding regions as compared to traditional flooding. Our analysis shows t hat the proposed scheme significantly outperforms CBT. (C) 2001 Academic Pr ess.