Introduction

I. Introduction

In the last five years, the commercial development of the Internet has brought into an enormous increase on its traffic. The Internet has grown from a simple information- sharing medium for academia and the scientific world to a mainstream communication tool for companies and people. New E-commerce applications, information services, community services, and financial services have grown all over the world around this powerful new medium.

One of the recent services provided over the Internet is the broadcasting of news, events, financial information and real-time data. These bandwidth-hungry multimedia applications and large-scale news broadcasts are backing network and service providers into a corner. The heat is on to come up with a solution that will allow broadcasting over the Internet without the escalation in data traffic. One possible solution to this problem is the multicasting transmission scheme.

Multicasting reduces the escalation of data traffic because it requires the transmission of a unique packet by the source and replicates this packet only if necessary. In 1992 the IP Multicast Backbone (MBONE), a virtual network layered on top of the physical Internet, was created to test and refine IP multicast technologies and the transmission of IP multicast packets. A schematic representation of the multicasting model can be seen in figure 1.

Figure 1: The unicast transmission sends multiple copies of data, one copy for each receiver. The

Multicast transmission sends a single copy of data to multiple receivers.

Unicasting and Multicasting - Advantages and Disadvantages

Unicasting is a communication method in which a source host sends a stream of data only to a single destination host. The Unicasting communication method is ideal for on-demand applications but is inefficient when the stream of data is delivered to many hosts at the same time. Broadcasting to many hosts over the Internet is better achieved through the multicasting communication method in which a source host sends a message to a group of destination hosts. The three major advantages of the multicasting model are:

Enhanced efficiency through network traffic control and server/CPU loads reduction.

Optimized performance through the elimination of traffic redundancy.

Distributed application making multi-point applications possible.

Figure two shows how the streaming of an audio file at 8 KBPS to many clients can be more efficiently achieved through the multicasting model compared to the Unicasting model.

Figure 2: Bandwidth utilization using multicast vs. unicast

Applications of the Multicasting Communication Model

Many new multi-point applications are emerging as demand for multicasting content grows. We can divide these applications into two major areas:

Real-time applications such as live broadcasts, financial data delivery, whiteboard collaboration and videoconferencing.

Non-real-time application such as file transfer, data and file replication, and on-demand broadcasting.

For the purpose of this paper, we will focus our attention to the analysis of broadcasting services over the Internet using IP multicasting technology.