Multicast Routing Algorithms and Protocols: A Tutorial

90 ulticasting is the ability of a communication network to accept a single message from an application and to deliver copies of the message to multiple recipients at different locations. One of the challenges is to minimize the amount of network resources employed by multicasting. To illustrate this point, let us assume that a video server wants to transmit a movie to 1000 recipients (Fig. 1a). If the server were to employ 1000 separate point-to-point connections (e.g., TCP connections), 1000 copies of the movie may have to be sent over a single link, thus making poor use of the available bandwidth. An efficient implementation of multicasting permits much better use of the available bandwidth by transmitting at most one copy of the movie on each link in the network, as shown in Fig. 1b. Recently, there has been a lot of research in the area of multicast communication. Although many excellent surveys and books exist which examine various aspects of multicasting [1–6], in the course of our studies we have found a need for a tutorial-cum-survey of the various multicast routing algorithms and their relationship with multicast routing protocols. In this work we present a tutorial-cum-survey of the following two important topics in multicasting: • Multicast routing algorithms • Multicast routing protocols Communication networks can be classified into two categories: local area networks (LANs) and wide area networks (WANs). A LAN spans a small geographical area, typically a single building or a cluster of buildings, while a WAN spans a large geographical area (e.g., a nation). Often, nodes connected to a LAN communicate over a broadcast network, while nodes connected to a WAN communicate via a switched network. In a broadcast LAN, a transmission from any one node is received by all the nodes on the network; thus, multicasting is easily implementMulticast Routing Algorithms and Protocols: A Tutorial