Computer Networks

Computers on a network are sometimes called nodes. To network is to connect two or more computers together with the ability to communicate with each other. A global network connects millions of computers. More than 100 countries are linked into exchanges of data, news and opinions. Unlike online services, which are centrally controlled, the Internet is decentralized by design. Each Internet computer, called a host, is independent. Its operators can choose which Internet services to use and which local services to make available to the global Internet community. When a group of two or more computer systems linked together they are considered to be in a network. There are many types of computer networks, including:

• Local-area networks-LANS: The computers are geographically close together (that is, in the same building).
• Wide- area networks - WANS: The computers are farther apart and are connected by telephone lines or radio waves.
• Campus-area networks- CANS: The computers are within a limited geographic area, such as a campus or military base.
• Metropolitan- area networks- MANS: A data network designed for a town or city.
• Home- area networks- HANS: A network contained within a user's home that connects a person's digital devices.

In addition to these types, the following characteristics are also used to categorize different types of networks:

• Topology: The geometric arrangement of a computer system. Common topologies include a bus, star and ring.
• Protocol: The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for personal computers is the IBM token-ring network.

Architecture: Networks can be broadly classified as using either a peer to peer or client to server structure.

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