Networks

Networks

1. Types

   • Bus
     • All the workstations, servers and printers are joined to one cable (the bus).
     • It is easy to install it is cheap to install as it doesn't require much cable
     • If the main cable fails or gets damaged the whole network will fail As more workstations are connected the performance of the network will become slower Because of data collisions every workstation on the network "sees" all of the data on the network – this is a security risk
   • Star
     • It is very reliable – if one cable or device fails then all the others will continue to work. It is high-performing as no data collisions can occur
     • each device on the network has its own cable that connects to a switch or hub.
     • It is expensive to install as this type of network uses the most cable (network cable is expensive). Extra hardware is required (hubs or switches) which adds to cost. If a hub or switch fails, all the devices connected to it will have no network connection
   • Ring
     • Each device (workstation, server, printer) is connected to two other devices - this forms a ring for the signals to travel around.
     • This type of network 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.
     • If the main cable fails or any device is faulty, then the whole network will fail.

2. Advantages

   • Sharing devices such as printers saves money.
   • Site (software) licences are likely to be cheaper than buying several standalone licences.
   • Files can easily be shared between users.
   • Network users can communicate by email 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.

3. Disadvantages

   • Purchasing the network cabling and file servers can be expensive.
   • Managing a large network is complicated, requires training and a network manager usually needs to be employed.
   • If the file server breaks down the files on the file server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but are isolated.
   • Viruses can spread to other computers throughout a computer network.
   • There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, eg a firewall.

4. WAN

   • A WAN covers a large geographical area. Most WANs are made from several LANs connected together.
   • Examples
     • The Internet
     • A network of bank cash dispensers

5. LAN

   • A LAN covers a small area such as one site or building, eg a school or a college.
   • Examples
     • A school network
     • Home WIFI
     • LAN'S are often connected to WAN'S

6. Components

   • Switch
   • Network interface card (NIC)
   • Gateway
   • Router (generally located at gateways)
   • Bridge
   • Hub

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