Multicast Routing Protocols in Mobile Ad Hoc Networks: A Comparative Survey and Taxonomy <s> Dynamic Core-Based Multicast Routing Protocol (DCMP) <s> Ad hoc wireless networks are self-organizing dynamic topology networks formed by a collection of mobile nodes through radio links. Minimal configuration absence of infrastructure and quick deployment make them convenient for emergency situations other than military applications. Multicasting plays a very crucial role in the application of Ad hoc networks. As the number of participants increases scalability of the multicast protocol becomes an important issue. Among the existing multicast protocols On Demand Multicast Routing Protocol (ODMRP) perfo exhibits a high packet delivery ratio even at high mobility. But ODMRP suffers from higher control overhead as the network size and the number of sources increase.In this paper we propose an efficient multicast routing protocol for Ad hoc wireless networks. This protocol reduces the control overhead by dynamically classifying the sources into Active and Passive categories. The control overhead is significantly reduced by about 30% compared to ODMRP which contributes to the scalability of the protocol. We study the effectiveness of the proposed multicast routing protocol by simulation studies and the results show that the multicast efficiency is increased by 10--15% and packet delivery ratio is also improved at high network load. <s> BIB001 </s> Multicast Routing Protocols in Mobile Ad Hoc Networks: A Comparative Survey and Taxonomy <s> Dynamic Core-Based Multicast Routing Protocol (DCMP) <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. DCMP BIB001 is an extension to ODMRP BIB002 and attempts to reduce the number of senders flooding JREQ packets by selecting certain senders as cores. This reduces the control overhead and therefore improves the efficiency of the ODMRP multicast protocol. DCMP constructs a mesh similar to that in ODMRP. It reduces the number of sources flooding the JREQ by having three types of sources: active, passive, and core active. Only active sources and core active sources flood the JREQ. Packets initiated at passive sources are sent to the core active node (as a proxy for passive sources), which forwards them to the mesh. The number of passive sources a single core active source can serve must be limited for robust operation. The distance (number of hops) between a passive source and its core active node must also be limited to ensure that the packet delivery ratio is not reduced. Figure 18 reveals the mesh construction in DCMP, where the parameters MaxHop and MaxPassSize (the maximum number of passive sources, a limitation that allows the mesh to have enough forwarding nodes for robust operation) are set to two. Since S 2 and S 3 are at a hop distance of 2 from each other (which is equal to MaxHop), S 3 becomes passive and uses a proxy in the core active node S 2 . No other pair of sources is separated by a hop distance of less than 2, and so eventually S 1 becomes the active source, S 3 a passive source, and S 2 a core active source. The number of forwarding nodes is reduced, as compared to ODMRP BIB002 , without much reduction in robustness or packet delivery ratio. Discussion. DCMP does not entirely alleviate the drawback of ODMRP, which is multiple control packet floods per group, but it is still much more scalable than ODMRP. It also has a high delivery ratio compared to ODMRP. However, in the case of failure of the core active source, multiple multicast sessions will fail.