Multicast Routing Protocols in Mobile Ad Hoc Networks: A Comparative Survey and Taxonomy <s> Tree-Based Approach versus Mesh-Based Approach versus <s> In this paper we propose a multicast routing protocol for mobile ad hoc networks (MANETs). The protocol-termed differential destination mmulticast (DDM)-differs from common approaches proposed for MANET multicast routing in two ways. Firstly, instead of distributing membership control throughout the network, DDM concentrates this authority at the data sources (i.e. senders) thereby giving sources knowledge of group membership. Secondly, differentially-encoded, variable-length destination headers are inserted in data packets which are used in combination with unicast routing tables to forward multicast packets towards multicast receivers. Instead of requiring that multicast forwarding state to be stored in all participating nodes, this approach also provides the option of stateless multicasting. Each node independently has the choice of caching forwarding state or having its upstream neighbor to insert this state into self-routed data packets, or some combination thereof. The protocol is best suited for use with small multicast groups operating in dynamic networks of any size. <s> BIB001 </s> Multicast Routing Protocols in Mobile Ad Hoc Networks: A Comparative Survey and Taxonomy <s> Tree-Based Approach versus Mesh-Based Approach versus <s> Group communication has become increasingly important in mobile ad hoc networks (MANET). Current multicast routing protocols in MANET have a large overhead due to the dynamic network topology. To overcome this problem, there is a recent shift towards stateless multicast in small groups. We introduce a small group multicast scheme, based on packet encapsulation, which uses a novel packet distribution tree construction algorithms for efficient data delivery. The tree is constructed with the goal of minimizing the overall bandwidth cost of the tree. Two construction algorithms, for a location-guided k-ary (LGK) tree and a location-guided Steiner (LGS) tree, utilize the geometric locations of the destination nodes as heuristics to compute the trees. They are accompanied by a hybrid location update mechanism to disseminate location information among a group of nodes. Our simulation results show that LGS tree has lower bandwidth cost than LGK tree when the location information of the nodes is up-to-date, and its cost is similar to that of an optimal Steiner multicast tree. When location information of the nodes is out-dated, LGK tree outperforms LGS tree due to its lower computational complexity. <s> BIB002 </s> Multicast Routing Protocols in Mobile Ad Hoc Networks: A Comparative Survey and Taxonomy <s> Tree-Based Approach versus Mesh-Based Approach versus <s> Many potential applications of mobile ad hoc networks (MANETs) involve group communications among the nodes. Multicasting is an useful operation that facilitates group communications. Efficient and scalable multicast routing in MANETs is a difficult issue. In addition to the conventional multicast routing algorithms, recent protocols have adopted the following new approaches: overlays, backbone-based, and stateless. In this paper, we study these approaches from the protocol state management point of view, and compare their scalability behaviors. To enhance performance and enable scalability, we have proposed a framework for hierarchical multicasting in MANET environments. Two classes of hierarchical multicasting approaches, termed as domain-based and overlay-based, are proposed. We have considered a variety of approaches that are suitable for different mobility patterns and multicast group sizes. Results obtained through simulations demonstrate enhanced performance and scalability of the proposed techniques <s> BIB003
Hybrid Approach versus Stateless Approach. Based on how routes are constructed for the members of the multicast group (network topology), multicast routing protocols for MANETs are classified according to the following types of approach. Tree-based, in which a single path between sourcedestination pairs is established. There are two kinds of Treebased approaches: Source-Tree-based and Shared-Tree-based. In the Source-Tree-based approach (persource tree), each source node creates a single multicast tree spanning all the members in a group. Usually, the path between the source and each member is not the shortest. In the Shared-Treebased approach, only one multicast tree is created for a multicast group which includes all the source nodes. This tree is rooted at a node referred as the core node. Each source uses this tree to initiate a multicast. Compared to the Source-Tree-based approach, the Shared-Tree-based approach is less efficient in multicast. In this one, the path between the source and the destination in the pair is not the shortest, but has a single point of failure and more overhead, since it maintains more routing information. In addition, the traffic is aggregated on the shared (backbone) tree rather than evenly distributed throughout the network, which gives it low throughput. Moreover, multicast protocols using a Shared-Tree-based approach require proper protocol operation to manage network partitions and mergers, since multicast group members may be separated into several disconnected partitions. However, multicast protocols intended for a Source-Tree-based approach do not require such protocol operations, because only the partition that includes the source maintains the multicast tree. In addition, the Source-Tree-based approach has a scalability 6 EURASIP Journal on Wireless Communications and Networking problem, but better throughput, since the traffic is evenly distributed throughout the networks. In the Mesh-based approach, a multicast mesh connecting a source to all receivers in the network is constructed. There are multiple paths connecting the source and destination in the pair. These redundant paths provide more robustness (resilient to link failure) and higher packet delivery, but, at the same time, they introduce capacity wastage, power inefficacy, and more overhead because of data packet duplication. In contrast, the Tree-based approach is both capacity and power efficient, but more susceptible to link failure because of lack of node mobility. Finally, the Mesh-based approach is much more suitable than the Treebased approach for MANETs. In order to achieve both robustness and efficiency, the Hybrid approach attempts to combine both the Mesh-based and the Tree-based approaches. Both these approaches have an overhead which is used to construct and maintain the delivery of the multicast tree or mesh, especially in an environment with frequent mobility. The Stateless approach is introduced to minimize the effect of this BIB001 BIB002 BIB003 . Instead of maintaining the routing information at every forwarding node, a source explicitly mentions the destination list in the packet header, and so this approach is intended for a small multicast group.