Networks

By Jonathan Russell

Lan

A local area network (LAN) is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media. The defining characteristics of LANs, in contrast to wide area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines.



WAN

A Wide Area Network (WAN) is a network that covers a broad area (i.e., any telecommunications network that links across metropolitan, regional, or national boundaries) using private or public network transports. Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. The Internet can be considered a WAN as well, and is used by businesses, governments, organizations, and individuals for almost any purpose imaginable.


Advantages and Disadvantages of a Network

Advantages

Sharing devices such as printers saves money.

Site (software) licences are likely to be cheaper than buying several standalone licences.

Files can easily be shared between users.

Network users can communicate by email and instant messenger.

Security is good - users cannot see other users' files unlike on stand-alone machines.

Data is easy to backup as all the data is stored on the file server.


Disadvantages

Purchasing the network cabling and file servers can be expensive.

Managing a large network is complicated, requires training and a network manager usually needs to be employed.

If the file server breaks down the files on the file server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but are isolated.

Viruses can spread to other computers throughout a computer network.

There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, eg a firewall.

Bus Network

In a bus network all the workstations, servers and printers are joined to one cable (the bus). At each end of the cable a terminator is fitted to stop signals reflecting back down the bus.

Ring Network

In a ring network each device (workstation, server, printer) is connected to two other devices, this forms a ring for the signals to travel around. Each packet of data on the network travels in one direction and each device receives each packet in turn until the destination device receives it.

Star Network

In a star network each device on the network has its own cable that connects to a switch or hub. A hub sends every packet of data to every device, whereas a switch only sends a packet of data to the destination device.