Network

What is a Network?

A network is two or more computers, or other electronic devices, connected together so that they can exchange data.

For example a network allows computers to share files, users to message each other, whole room of computers to share a single printer, etc.

Network connections between computers are typically created using cables (wires). However, connections can be created using radio signals (wireless / wifi), telephone line (and modems) or even, for very long distances, via satellite links.

Advantages of networks Disadvantages of networks

Easily share files and data.Share resources such as printers and internet connections.

Communicate with other network users (e-mail, instant messaging, etc.

Make use of online services such as shopping or banking.

Get access to a huge range of information for research.

Access different form of entertainment (games, video, etc.)

Join online communities (e.g. MySpace, Facebook, etc.

The computer is venerable to hackers. If the network breaks, many tasks

become very difficult. The computer can more easily be

attacked by a virus. Information found on the internet is

not always accurate or reliable.

Types of NetworkLocal Area Network (LAN) A local area network is a network confined to one building or site.Often a LAN is a private network belonging to an organisation or business.Because LANs are geographically small, they usually use cables or low-power radio (wireless) for the connections.

Network TopologiesThere are three common network topologies...

Bus NetworkIn this type of network, a long, central cable, the ‘bus’ is used to connect all of the computers together. Each computer has a short cable linking it to the ‘bus’.Advantages of Bus Network disadvantages of Bus Network Is cheap to install (just one long cable) Easy to add extra workstation. Uses less cables then a star network. Best choice for temporary networks.

If there is a problem with the central cable, the entire network stops working

If there are a lot of workstations on the network, data can travel slowly.

Data collisions can happen as the network becomes busy

Low security - every workstation can see all of the data in the network

Limited cable length and a maximum number of workstations

Ring Network

In a ring network layout, all of the computers are connected to one another in a circle. The data passes from one computer to the next one and then all the way around the ring layout until it reaches the destination computer.

Advantages of Ring Network disadvantages of Ring Network Transmission of data is fairly simple

as it only travels in one direction No data collisions Extra computers can be added easily

with little effect on performance - although you have to shut down the network to be able to do this.

If a single machine is switched off, the network doesn't work

If a cable breaks, the network doesn't work

Data must pass through every computer until it reaches its destination. This can make it slower than other network layouts.

If there are any problems with the network, they can be difficult to identify the cause.

Star Network

In this type of network every computer is connected to a central device. The device passes messages between computers. At the centre of a star network you might use a hub (cheap, but slower) or a switch (more expensive, but faster).

Advantages of Star Network disadvantages of Star Network Star networks are very reliable. If

one connection fails, it does not affect other users

Very few data collisions as each workstation has its own cable to the server

Good security - no workstation can interact with another without going through the server first

The most expensive network layout to install because of the amount of cables needed

Installing the network usually needs experts to set it up

Extra hardware such as hubs and switches may be needed

If the server crashes or stops working then nobody will be able to access their files or use the network.