Network hardware
Introduction
What typical hardware is used on a network? If you had a group of stand-alone PCs, what hardware and software would you need to connect them all together to make a network?
Physical connections
To link computers together into a network, you need to connect them together. This might simply be done by using some cable to make a physical connection. You would need to think carefully about where the cables will actually go so that they don't suffer from electrical interference and once in position, they are not so easy to change. One of the most commonly used kind of cable is called Category 5, or Cat 5 for short. Cat 5 cable is made up of 4 twisted pairs of copper wire to reduce interference. It's cheap, flexible and is widely used for networks because it can carry a lot of data (referred to as 'bandwidth'). A type of connection that can carry even higher bandwidths is fibre optic cable, although it is more expensive and not quite as strong as Cat 5. This is a glass cable surrounded by protective material. Electrical data is converted to and from light using a wide range of frequencies and bounced down the cable. It doesn't suffer from electrical interference because light is used rather than electrical signals. Coaxial cable (the cable that a TV aerial uses) is also used for some networks, as it's very strong and protects from electrical interference.
Switch (and hub)
The PCs on a network are connected to a 'switch'. A switch manages lots of connections with computers at the same time and lets them all communicate with the server (see below). This job was often done by a 'hub' in the past, but hubs could not handle lots of connections at the same time with many different computers. As technology improved, hubs became more obsolete and switches are almost always used now. Having said that, the terms 'hub' and 'switch' are often used interchangably.
Wireless connections
You could also use wireless technology to connect the computers together. To connect a laptop to a network, you need a WAP, or Wireless Access Point. These are set up so that laptops can connect to them, usually by the user of the laptop typing in a password. WAPs can be set up so that users don't have to enter a password (called an 'open network') but that means that anyone within range of the WAP can get access to the network. Hotspots can be open public networks or a service that you have to log in to, but they present a serious security risk. You should always assume that someone is capturing your communications when using a hotspot and never use it for sending or receiving sensitive inofrmation such as financial information.
Bandwidth
With both physical and wireless connections, an important consideration is 'bandwidth'. Bandwidth is the term used to describe the amount of data transmitted across a network through a communications channel, such as a cable. Transmitting data such as music or video is a high bandwidth activity. Transmitting word-processed documents is a low bandwidth activity. Different interconnections are able to carry different bandwidths.
Bandwidth isn't about the speed data travels, but about the volume of data that can be sent. If you think of water pipes for a moment. The bigger the water pipe, the more water you can send in one second (so the higher the water 'bandwidth'). If the pipe has a smaller diameter, then you can send less water per second down it (smaller water 'bandwidth'). However, the water in both cases travels at the same speed!
Network adapters (also called network cards)
Each computer that is going to be part of a network needs to be able to make a connection to the network. To do this, each computer or laptop needs a network adapter. This is usually but not always fitted inside a computer. The network adapter provides:
-
- a physical means of connecting a computer to a network
- a way of splitting up data that you want to send across a network and then getting that data actually onto the network successfully
- a way of collecting ‘packets’ of data addressed to that particular computer from the network. Each network card has a unique identifier called a ‘MAC address’ that enables this to happen.
Server (or 'File server')
Computers on a client-server network are known as ‘clients’ and they are all looked after by a special computer known as a 'server'. Although a server is just like a normal computer it does have a huge hard disk compared to the clients. This is because it needs to store everyone's data files as well as store many applications centrally. The server will also have much more RAM than the clients and a very fast processor, to enable it to work as quickly as possible with many different clients at the same time. The server will usually have some kind of automated back-up hardware, to ensure that users' files are backed-up regularly.
Print server
Apart from the file server, there are other types of server. One of them is known as a 'print server'. This piece of hardware allows you to connect a printer to a network so that it can be shared by the clients on the network. Every time a job is sent to print, this piece of hardware puts it in a queue and takes charge of sending it to the printer.
Routers
This piece of equipment is usually used as a gateway, to allow a smaller LAN to connect to a larger network such as the Internet. It holds the address of each computer on the LAN so when some information such as an email or a web page comes into the LAN from the Internet, it knows where to send the information.
Modem
Another way of connecting a LAN to a larger network is to use a 'modem'. A modem uses the telephone network. Computer signals (digital) are converted to telephone signals, which are analogue and sent down the telephone wires. At the receiving end,, the analogue signals are collected by a modem and converted back into digital again for the receiving computer.
Network Operating System (NOS)
Hardware on its own is not enough! You need to also buy some software to allow the server to organise and manage the communications around the network and to allow the server to take responsibility for controlling access to the files held on its hard disk. This software is known as the ‘Network Operating System’, or NOS. Typically, the NOS controls access to the facilities on the network by making a user log in. They do this by providing each user with a user ID and a password, which they then have to type in when they want to use the facilities of the network.
ISP account
Of course, if you want to connect a network to the Internet then you need an Internet Service Provider (ISP) account. This is a company that acts as a door to the Internet. You sign up with an ISP for a fixed monthly or annual fee and they then allow you to access the Internet through them, either using your dial-up or your broadband connection.