During the last few years the Internet has grown tremendously and has penetrated all aspects of everyday life. Starting off as a purely academic research network, the Internet is now extensively used for education, for entertainment, and as a very promising and dynamic marketplace, and is envisioned as evolving into a vehicle of true collaboration and a multi-purpose working environment. Although the Internet is based on a best-effort service model, the simplicity of its packet-switched design and the flexibility of its underlying packet forwarding regime (IP) accommodate millions of users while offering acceptable performance. At the same time, exciting new applications and networked services have emerged,.
