LAN's

LANs – Local Area Networks – link computers within a limited area – an office or a building.

They can be built with two main types of architecture:

• peer-to-peer

  The computers have the same capabilities

• client-server

  One computer acts as a server containing the main hard disk and controlling the other workstations or nodes and all the devices linked in the network.

Each node (individual computer) in a LAN has its own CPU which executes programs, but it also is able to access data and devices anywhere within the LAN. This means that many users can share expensive devices, such as laser printers, as well as data. Users can also use the LAN to communicate with each other.

Computers in a LAN need to use the same protocol – the language or a set of rules that computers use to communicate with each other (TCP/IP in case of the Internet). Ethernet is one of most common protocols for LANs.

LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.

LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).

A router is a device needed to link a LAN to another network (Internet).

Intranet is network based on TCP/IP protocols belonging to an organization, usually a corporation, accessible only by the organization's members, employees, or others with authorization. An intranet's Web sites look and act just like any other Web sites.

Like the Internet itself, intranets are used to share information. Secure intranets are now the fastest-growing segment of the Internet because they are much less expensive to build and manage than private networks based on proprietary protocols.