Multicast routing is an effective way to establish the group communication when the same message or the same stream of data needs to be sent to multiple receivers. Multicast routing has attracted a lot of attention in group oriented computing due to supporting data transmission from a single source node to multiple destinations concurrently. The advantage of multicast routing lies in its capability of reducing the communication cost and saving the network resources by sending only one copy of the message over the shared link leading to different destinations. Generally speaking, this survey classifies the multicast routing protocols into four categories based on the underlying routing structure: tree-based, mesh-based, hybrid, and stateless multicast routing protocols. This survey summarizes the well-known most recent protocols of each category and compares their objectives, performances, advantages, and disadvantages. This survey study helps us to choose the best multicasting protocol for each network application with respect to the requirements of application.
Top1. Introduction
Multicasting is a technique for data routing in networks that allows the same message is forwarded to a group of destinations simultaneously. In mobile ad hoc networks (MANETs), the most challenging issue in multicast routing is to effectively handle the frequent and unpredictable topology changes caused by host mobility, link breakage and host failure. Multicasting is intended for group-oriented computing like audio/video conferencing, collaborative works, and etc. Multicasting is an essential technology to efficiently support one-to-many or many-to-many applications. Multicast routing has attracted a lot of attention in the past decade, due to it allows a source to send information to multiple destinations concurrently. Multicasting is the transmission of packets to a group of zero or more hosts called multicast group which is identified by a single destination address. A multicast group is a set of network clients and servers interested in sharing a specific set of data. A typical example of multicast groups is a commander and his soldiers in a battlefield. There are other examples in which multicast groups need to be established. Typically, the membership of a host group is dynamic: that is, the hosts may join and leave groups at any time. There is no restriction on the location or number of members in a host group. A host may be a member of more than one group at a time. A host does not have to be a member of a group to send packets to it. A multicast protocol has the objective of connecting members of the multicast group in an optimal way, by reducing the amount of bandwidth necessary but also considering other issues such as communication delays and reliability (Nadeem & Parthasarathy, 2006).
Multicast routing plays a critical role in most of the new applications such as web-base learning, video conference, and interactive multimedia games. Multicast routing in mobile ad hoc networks poses several challenges due to inherent characteristics of the network such as node mobility, reliability, and scarce resources. The main difficulty in designing a routing protocol for mobile ad hoc networks is the dynamically changing topology, due to the random movement of mobile nodes. The multicast routing protocols designed for wireless mobile ad hoc networks are fundamentally different from those for conventional infrastructure based networks in that these are self-configuring and formed directly by a set of mobile nodes without relying on any established infrastructure. In such networks, the heterogeneity of the hosts makes it difficult to achieve bandwidth efficiency and service flexibility.
In ad hoc networks, there exist several methods upon which classification of the multicast routing protocols is based. Classification based on the underlying structure of the multicast routes, based on the route acquisition time, based on multicast route initiation (based on the responsibility for route construction), and based on the forwarding state maintenance schemes are the well-known representative methods. Underlying multicast route structure is the most popular approach based on which the multicast routing protocols are classified. This classification considers the connectivity of the forwarding paths through which the multicast receivers are connected. This survey presents a new comprehensive classification of the multicast routing protocols based on the underlying route structure. In this classification, the multicasting protocols are categorized as tree-based multicast routing protocols, mesh-based multicasting protocols, hybrid protocols, and stateless protocols. This survey studies the most recent effective protocols of each category with the emphasis on the objectives, performances, costs, advantages, and drawbacks.
The rest of this paper is organized as follows. The multicast routing problem is defined in Section 2. In Section 3, the multicast routing protocols proposed for ad hoc networks are classified from several points of view. Section 4 presents a new classification of the multicast routing protocols based on the underlying routing structure and compares the existing multicasting schemes from this point of view. Section 5 concludes the paper.