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COMPUTER NETWORKS

A network is a group of computers or computer like devices that communicate to one another using a common transmission medium. Computers send requests and data through the transmission medium, usually network cables or optical fibres. Wireless networks use radio waves as the mode of transmission and are becoming increasingly common.

Resources made available on the network are accessible by the users of the networks, this include documents, images, video and audio clips. It is also possible to share software across the network and this can lead to a reduction in the maintenance of software on each computer on the network.

Devices on a network communicate to another by breaking down data into groups of electrical pulses which are known as packets. These packets contain information about the address of the source of origin of the packet and its destination. It is this information that is used by the network equipment to ensure that packet gets to its intended recipient.


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Network Classification

There are several types of networks available and a variety of ways in which they can be classified. The following three are just some of the classifications used are:

  • Topology
  • Size
  • Connection Medium

Topology

Networks classified by their topology are typically divided into two categories:

  1. Point-to-point networks: are networks where the devices are linked together between two end systems to create a star, lattice or hierarchical structure. There is a direct passage of packets to their recipients and there is no doubt where it cm from (as it cam only come from the other end of the communication link).

    A good example of a point-to-point network is two computers linked together using modems and a dedicated telephone. This can be found in some rural hospitals linking their computers to those of the larger urban centers close to them.

  2. Broadcast networks: are networks where a single communication channel is shared by all the computers on a network, hence packets from one computer is sent to all the computers on the network. The network topology using a bus or a token ring. It may also make use of wireless technologies for communication.

    Computers on the network read the header of all the packets sent to them. The header would contain the address information of the recipient, and only when the packets are addressed to them, will the computers then proceed to read the body of the packets.

    The broadcast network topology is favoured in building local area networks and wide area networks.

Size

Networks can also be classified according to the size of the area they cover. There are three common types of ‘area’ networks:

  1. Local Area Network (LAN): This network is confined to a relatively small area (from a few meters to a few kilometres apart). Must LANs can have two to several hundred computers connected to it and each computer is known as a node. These nodes are usually connected by Ethernet (special high-data-rate) cables, although wireless technology is increasingly being used to develop wireless LANs.

  2. Metropolitan Area Network (MAN): These are large networks that cover areas larger than those covered by LANs but smaller than those covered by wide area networks (WANs). MANs usually spans a city or university campus and that can be anything within a 5 to 50 kilometres diameter and they can also be a series of LANs that come together to form a larger network. MANs are implemented using technologies such as optical fibres, Asynchronous Transfer Mode (ATM), gigabit Ethernets and switched multi-megabit data services.

  3. Wide Area Network (WAN): Wide area networks cover a large geographical area, often across the world. Because of the large geographical are they cover, WANs make use of communication circuits from telephone companies or other communication carriers.

    WANs are usually owned by a single organisation, company or individual and when two or more of these networks connect together, they form what is known as an ‘Internetwork’, the most popular of these being the Internet.

    WANs owned by individuals and organisation are usually private, while public WANs include those that are owned by Internet Service Providers (ISPs).

Connection Medium

In terms of connection media, networks can be divided into wired and wireless networks.

  1. Wired networks: These make use of optical fibres, Ethernet cables and other communication cables to connect the computers onto the network.

  2. Wireless networks: These make use of wireless technologies to connect the computers onto the network. They are easier and cheaper to set up and usually tend to be the size of LANs, although wireless WANs are now available. It is not uncommon for both wired and wireless networks to be combined. In most cases, a wireless LAN (WLAN) is connected with a wired WAN. Wireless networks are especially important in organisations that need to implement wireless computing solutions.

 

 

QUICK LINKS
International Medical Informatics Association
American Medical Informatics Association
UK Health Informatics Society
Healthcare Information and Management Systems Society


Knowledge Center
Biomedical Informatics
Bioinformatics
Health Informatics
Healthcare Technologies
Software
Hardware
Networks
Hospital Information Systems


Computer Networks Topics
Client/Server Networks
Internet
Intranets and Extranets
Peer-to-Peer Networks
Thin Client Server Technology
Virtual Private Networks
Wireless Technology


Last Updated: 10 August 2006.



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