Multicast Routing Protocols in Mobile Ad Hoc Networks: A Comparative Survey and Taxonomy <s> Associativity-Based Ad Hoc Multicast (ABAM) <s> Multicast has emerged as a very desirable feature in communication networks. With multicast, data can be distributed to multiple recipients in an efficient and economical manner. We present a performance evaluation of a novel multicast routing strategy for a mobile ad hoc network environment, which is characterized by a highly-dynamic topology with constrained bandwidth and limited power. The associativity-based ad hoc multicast (ABAM) protocol establishes multicast session on demand and utilizes an association stability concept, which is introduced in the ABR protocol for mobile ad hoc unicast routing. The performance of ABAM is simulated and compared with a flooding-based multicast routing protocol. The results show impressive throughput and very low communication overhead. <s> BIB001 </s> Multicast Routing Protocols in Mobile Ad Hoc Networks: A Comparative Survey and Taxonomy <s> Associativity-Based Ad Hoc Multicast (ABAM) <s> An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile and hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation. <s> BIB002
Protocol Description. ABAM BIB001 is an On-Demand Sourcebased multicast routing protocol for mobile ad hoc networks. A multicast tree rooted at the multicast sender is established for each multicast session based primarily on association stability. Association stability helps the source to select routes to receivers which will probably last longer and need less reconfiguration. To initiate the multicast session, a multicast sender broadcasts a Multicast Broadcast Query (MBQ) message throughout the network. Nodes receiving the MBQ message will append their addresses and other information (route relaying load, associativity ticks, signal strength, power life) to the MBQ message before it is rebroadcast. Hence, each MBQ message accumulates information about the path traveled as it is forwarded. Multicast receivers will collect all the MBQ messages for the multicast group it wants to join. The most stable route back to the multicast sender will be chosen from all these possible routes and the MBQReply message will be sent back to the multicast sender via the chosen path. Several MBQ-Reply messages, one from each multicast receiver, will be received by the multicast sender. With all received MBQ-Reply messages, the multicast sender will compute a stable multicast tree that results in shared links and generate an MC-Setup message to establish the multicast tree. That message will be propagated to all nodes along the tree, and these nodes will be programmed to participate in multicast forwarding. The tree construction phase is illustrated in Figure 3 . A broken link is detected and repaired by the upstream node. When the upstream node, say node X, detects a broken link, it sends a LocalQuery packet (TTL = 1) searching its downstream node (receiver R 2 ). When the downstream node receives a LocalQuery packet, it replies with a LocalQuery-Reply packet and rejoins the multicast group. If the upstream node failed to find its downstream node, the next upstream node is responsible for repairing the broken link. This process terminates at a branch node Y (a node connecting many receivers). After that, R 2 sends a JoinQuery packet to join the multicast group. If a branch node Y moves, it sends a LocalQuery packet (TTL = 2, the number of hops to the furthest affected receiver on that broken branch) searching for the two receivers R 1 and R 2 . When a receiver leaves a multicast group, it sends a Leave message, which results in the branch being pruned (if there are no other receivers in that branch). When a multicast group has no more receivers, that is, when all the members have decided to leave the group, the tree will be pruned incrementally. The multicast tree can also be deleted when the source no longer wishes to act as a multicast sender. It can do this by sending a multicast Delete message to prune the tree. Discussion. ABAM introduces less control overhead traffic and achieves a higher packet delivery ratio in comparison with ODMRP BIB002 , due to the stability of the path between the source and destination nodes. At the same time, the path may be long, and some latency in delivering the data packets will be incurred. In addition, ABAM suffers from scalability issues.