In the age of multimedia and high-speed networks, there are many applications that involve sending information to a selective, usually large, number of clients. Common examples of such applications include audio/video conferencing, distance learning, video-on-demand, distributed interactive games, data distribution, service location/discovery, collaborative computing, collaborative visualization, distributed simulation, communicating to dynamic group, and so on. To support such applications, multicast is considered a very efficient mechanism (Lao 2005) since it uses some delivery structures to forward data from senders to receivers, with the aim that the overall utilization of resources in the underlying network is minimized in some sense (Oliveira 2005). For example, multicast is heavily used for mass media TV distribution which can be seen from a survey conducted by NAB Research and Planning (NAB 2005). NAB Research and Planning conducted this survey in July 2005 of all U.S. full-power commercial television stations on their plans for DTV (Digital TV) multicast services. Among the 450 response stations, 50% of stations are currently multicasting, and 79% among non-multicasting stations are considering multicasting at some point in the future.
Key Terms in this Chapter
Internet Protocol (IP) Multicast: A routing technique that allows IP traffic to be sent from one source or multiple sources and delivered to multiple destinations. Instead of sending individual packets to each destination, a single packet is sent to a multicast group, which is identified by a single IP destination group address. IP Multicast is a bandwidth-conserving technology aiming that the overall utilization of resources in the underlying network is minimized.
Domain: A domain or an autonomous system (AS) is a network or group of networks under a common routing policy, and managed by a single authority.
Multi-Protocol Label Switching (MPLS): A datacarrying mechanism which emulates some properties of a circuit-switched network over a packet-switched network. MPLS operates at a OSI model layer that is generally considered to lie between traditional definitions of Layer 2 (data link layer) and Layer 3 (network layer), and thus is often referred to as a “Layer 2.5” protocol. It was designed to provide a unified datacarrying service for both circuit-based clients and packet-switching clients which provide a datagram service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames.
Quality of Service (QoS): QoS represents the set of techniques necessary to manage network bandwidth, delay, jitter and packet loss. From a business perspective, it is essential to assure that the critical applications are guaranteed the network resources they need, despite varying network traffic load.
Routing Tables: Used to direct forwarding by matching destination addresses to the network paths used to reach them. The construction of routing tables is the primary goal of routing protocols.
Routing: A means of discovering paths in computer networks along which information can be sent. Routing directs forwarding, the passing of logically addressed packets from their source toward their ultimate destination through intermediary nodes, called routers. Forwarding is usually directed by routing tables within the routers, which maintain a record of the best routes to various network destination locations. Thus, the construction of routing tables is important to efficient routing.
Inter-Domain Routing: The Internet is an interconnection of multiple networks called domains or autonomous systems (ASes). Inter-domain routing in the Internet takes place between autonomous routing domains and routing information must be exchanged between domains to ensure that a host in one domain can reach another host in a remote domain.