Networks - LANs and WANs 5.3.4

Types of networks:

Networks are divided into two types, a LAN (Local Area Network) or a WAN (Wide Area Network).

LANs - Local Area Networks

Definition - A LAN is a network that is limited to an area such as a building or school.

In a LAN, computers and hardware such as printers can be connected by cable (copper wiring), fibre optic cabling (glass fibres) or using a wireless (radio waves) connection.

Advantages of LANs:

• Hardware such as printers can be shared so individual workstations do not need their own printer. When they print, the data is stored in a queue on a server. The data is then passed to the printer.
• All the users work can be stored in a central place (the dedicated file server) so a user can access their work through any computer on the network.
• Software can be shared, software packages are stored on the server and downloaded to workstations as requested. Note that a licence still has to be bought for each copy of the software needed.
• Data can be shared because database files stored in the server are available to users around the network; data from CD-ROMs can also be shared across the network.
• Central back-up can take place automatically at regular intervals. A user will usually be able to retrieve work that has been deleted by mistake.
• Messages can be sent to people working at other computers on the network which can save time and paper.
• It is possible to set up a local intranet such as that on the KLB school network. The web pages of information can be accessed only over the LAN.  An intranet is free because it does not involve phone links.
• There is control over users’ access rights to programs and data.

Disadvantages of LANs:

• Printing can be slow. Where a lot of workstations are served by only one or two printers, long print queues may develop.
• A virus can spread more easily. If a virus gets into one computer, it is likely to spread quickly across the network because it will get into the central backing store.
• As data is shared there is a greater need for security. Users of the network have to have authentication techniques such as user ids and passwords. Unique user ID's control access to the files and settings on the network while passwords prevent unauthorised users from logging onto the network.  Data may also have to be encrypted so that it is meaningless if intercepted.
• If the server fails, all the workstations are affected. Work stored on shared hard disk drives will not be accessible and it will not be possible to use network printers either.
• The cost of installing the equipment is greater. Cabling can be expensive to buy and to install.
• Damage to cables can isolate computers. Some sections of the network can become isolated and will not be able to communicate with the rest of the network.
• Because networks can be complicated to maintain, a network manager may be need to be employed to run the system.

WANs - Wide Area Networks

Definition - a Wide Area Network is not confined to one building. The computers and terminals forming part of the network can be spread around the world.

External communication links such as satellites, microwaves, telecommunication links and optical fibre will be used to connect the parts of a WAN. The connection must normally be paid for because the links are external.

The Internet is a worldwide WAN and a LAN can be connected to it using a router.

Advantages of WANs:

• These are similar to those of LAN's except the scale of sharing etc. becomes far greater and can be world-wide.

Disadvantages of WANs:

• Again these are similar to those of LAN's except that issues such as security become even more important as potential hackers could break into a computer system from anywhere in the world rather than having to physically be in a building.
• Encryption of secure data such as financial transactions is necessary because it is even easier to intercept data.

Revision points - you should be able to do the following:

• Explain what is meant by a network and know the benefits of networking computers 
• Define a LAN (Local Area Network) and a WAN (Wide Area Network) and discuss the advantages and disadvantages of each

Questions: (Check Answers)

1. What is a network?

2. Explain what a Wide Area Network is.

3. State one advantage and one disadvantage of a WAN.

4. When using a LAN, why is it necessary to have a password?

5. Describe the software that makes up a network.

6. Describe the devices that make up a typical network.