Internet

The Internet is the world’s biggest computer network, designed essentially as a network of networks. It uses TCP/IP technology, a set of protocols for network communications. Some of the many services that the Internet offers are email, chat, file sharing and access to hyperlinked documents (the World Wide Web).

The Internet is freely accessible. The Internet has grown exponentially since its creation, not only in the number of computers attached to it, but also in the number of services offered by it. The Internet had about 16 million users in 1995 and reached 1.1 billion users by December 2006. The Internet has revolutionized the way people communicate, both locally and around the globe.

Hosts and routers are two basic elements that the Internet requires. Hosts are mostly computers but can also be cell phones, satellites, personal digital assistants (PDA) and other devices. Hosts send and receive information in formatted blocks called packets. Routers receive the packets and direct them to their specific destination. The Internet relies on this "packet-switching" technology.

All hosts and routers have IP addresses and some, such as servers, have a name or Uniform Resource Locator (URL). The speed of the links, as well as the Internet in general, has grown amazingly fast, from an average of 56 kbps (1 kbps = 1000 bits per second) in January 1993 to 60,000 kbps by Fall 2006, more than a 1000-fold increase.

There are two main types of hosts: clients and servers. Clients are computers that receive information, and servers are computers that store and provide the information that is needed or requested. This distinction has blurred with the advance of P2P technology, in which clients are also used as servers to provide information to other clients.