LANs and WANs Coatbridge High School Computing Department

What is a Network? A network is a linked set of computer systems that are capable of sharing programs, data and sending messages between them. When a computer is not part of a network, it is called a stand alone computer. A local area network (LAN) covers a small area such as a room or a building. A wide area network (WAN) covers a larger geographical area.

Local Area Networks Each computer on a local area network is called a station. Usually one station on the network is set aside as the file server. Advantages of local area networks:  You can share data and programs between stations.  Everyone on the network can share peripherals such as printers.  An electronic mailing service can be operated.  By using passwords the data can be kept secure.  Different users can have different levels of access.  A user can access their files from any computer on the network.  Many users can work on the same document simultaneously.

Transmission media for LANs Stations on a LAN can be connected using cables or wireless signals as the transmission medium. Two types of cable are unshielded twisted pairs of copper wire (UTP) and optical fibre. Wireless networking includes infrared communication, Bluetooth, WiFi, microwave transmission and satellite links.

Transmission media for WANs WANs use telecommunication links to transmit and receive data. Telecommunications is a general term that describes the communication of information over a distance. Telecommunication links include Microwave Transmission, Satellite Links and Optical Fibre. Submarine cable

Network Security Security methods include passwords, encryption and physical. You should change your password regularly so that no one else can discover it. You shouldn’t choose a password that would be easy for someone to guess. Encryption means putting data into a code to prevent it being seen by unauthorised users. Physical security prevents unauthorised users from getting access. Locking a computer or disks away will prevent physical access.

Client and Server Networks A client and server network is a method of network organisation in which network stations or clients make use of resources available on one or more servers. Desktop computers are the most common type of client on this network. A network interface card (NIC) is required in order to connect to a network. A file server provides central disk storage for user’s programs and data on a network. Multi-access means that many users may be on-line to a computer system at the same time. E.g. airline reservations, cashcard machines.

Social, Legal and Ethical Issues Teleworking is the process of using a wide area network to work from home rather than an office. Use of wide area networks can bring social benefits in that it can improve communications with remote areas and reduce social isolation. Some people believe than WANs can also increase social isolation. Laws which may affect the use of computers include the Computer Misuse Act, the Copyright, Designs and Patents Act and the Data Protection Act. Ethical issues are concerned with people’s judgement as to what is right or wrong. Ethical issues of networks include invasion of personal privacy, censorship and freedom of speech.