LANs – Local Area Networks

A LAN is confined to a small area, usually within a single building.

A line (bus) topology is the cheapest in terms of cabling costs.

Computer networks - LAN and WAN

A description of a Local Area Network (LAN) in an office setting, and a Wide Area Network (WAN). Businesses and other organisations often link computers together to make communication more efficient. Each computer is linked to a central server which acts as a go-between within this LAN and beyond. A WAN links computers together over a wide geographical area. The internet is the ultimate WAN. Browsers are software packages which allow you to navigate around the internet.

Advantages of LANs:

You must be able to describe a system in terms of advantages and disadvantages. Do not always remember the good points.

• Costly resources such as printers can be shared by all of the computers. This means that better quality printing is available to everyone because one or two expensive, high specification printers can be bought instead of several cheaper, lower specification models. A line (bus) topology is the cheapest in terms of cabling costs.
• Central backing store can be provided in one place (the dedicated file server) so all work is saved together. An individual user can load his or her work on any computer on the network.
• Software can be shared, and upgrading is easier too. This gives continuity in the workplace. However, sharing software is often not much cheaper than providing a copy for each machine because a licence has to be bought for each copy of the software needed.
• 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.
• Data can be shared across the network. For example, this would allow several people to work on the same project. The setting up of hierarchical system passwords to allow different users different access is the key to controlling access to most company databases.
• If the data being shared is in a database, several people will be able to use the database at the same time, but they will not be able to edit the same record at the same time. When a record is opened by one user, it is locked so that other people cannot try to edit it at the same time. This avoids the confusion that would result if several people were trying to edit data at the same time. Once the first user has completed and saved the operation, the record is unlocked again.
• Local email messages can be sent to people working at other terminals on the network. This can save time and ensures that messages get to the right place.
• There may be a local Intranet. This works like the World Wide Web, with pages of information. The difference is that the pages can be accessed only over the LAN. As it does not involve phone links, an Intranet is free.

Disadvantages of LANs:

• The use of email within the network can lead to problems of time wasting as people send messages that do not relate to work. Some companies discourage the use of in-house email because they believe that it is better for employees to communicate face to face.
• Where a lot of terminals are served by only one or two printers, long print queues may develop, causing people to have to wait for printed output. Rings provide the fastest form of local area networking.
• Network security can be a problem. 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.
• Users of the network have to have user names and passwords. Some users are not very good at keeping passwords secret, or they may use passwords that are easy to guess. Other people can then log onto the network.
• If the dedicated file server fails, work stored on shared hard disk drives will not be accessible and it will not be possible to use network printers either.
• Cabling can be expensive to buy and to install. In a busy office situation, cabling must often be placed under the floor so that people will not trip over it. If connecting cables are damaged, some sections of the network can become isolated. They will not be able to communicate with the rest of the network. Try to remember at least three advantages and three disadvantages for each system. Look carefully at the exam question to see how many points the examiner wants.