1. Networks 1
Key Revision Points

2. Key Points to Learn Key Terms
Advantages/Disadvantages of a LAN vs. stand-alone computers
3 topologies – benefits and drawbacks of each

3. Definitions
A computer network is a number of computers linked together to allow them to share resources. Networked computers can share hardware, software and data.
Most computer networks have at least one server. A server is a powerful computer that provides one or more services to a network and its users. For example, file storage and .
A LAN (Local Area Network) covers a small area such as one site or building, e.g. a school or a college.
A WAN (Wide Area Network) covers a large geographical area. Most WANs are made from several LANs connected together.

4. LAN and WAN

5. Benefits Sharing devices such as printers saves money.
Advantages
Sharing devices such as printers saves money.
Files can easily be shared between users.
Network users can communicate by and instant messenger.
Security is good - users cannot see other users' files unlike on stand-alone machines.
Data is easy to backup as all the data is stored on the file server.

6. Drawbacks
Disadvantages
Purchasing the network cabling and file servers can be expensive.
Managing a large network is complicated. A network manager usually needs to be employed.
If the file server breaks down the files on the file server become inaccessible.
There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, eg. a firewall.

7. Bus Network Benefits Easy to install new devices on the network
Cheap to install, as it doesn’t require much cable
Drawbacks
As more workstations are connected the performance of the network will become slower because of data collisions
If the main cable fails or gets damaged the whole network will fail

8. Ring Network
Benefits
Can transfer data quickly, even if there are a large number of devices connected.
Because the data only flows in one direction, so there won’t be any data collisions.
Drawbacks
If the main cable fails or any device is faulty then the whole network will fail.

9. Star Network
Benefits
Very reliable – if one cable or device fails then all the others will continue to work
High performing as no data collisions can occur
Drawbacks
Expensive to install as this type of network uses the most cable (network cable is expensive)
If a hub or switch fails all the devices connected to it will have no network connection