Higher Grade Computing Studies 5. Networks

1. Higher Grade Computing Studies5. Networks Categories of Computer - Network Computer • Computers are networked for the purpose of sharinghardware, software and data. • Alternatively, the main reason for networking may be the supply of applications softwareto a number of users or to allow them access to important shared documents.

2. Higher Grade Computing Studies5. Networks Networks - LANs • A Local Area Network is a network of computers that are all situated close together for example in a room or building. Since the distance between computers is relatively small wire cables are frequently used to connect the computers together. LANs are usually set up to allow users to share data, communicate and share expensive peripherals.

3. Higher Grade Computing Studies5. Networks Networks - LANs

4. Higher Grade Computing Studies5. Networks Networks - WANs • This is a network of computers connected across a distance. Telephone lines, satellites or other communication technology is required for WANs to work. Most major companies need a WAN in order to communicate with other branches either nationally or internationally.

5. Higher Grade Computing Studies5. Networks Networks - WANs

6. Higher Grade Computing Studies5. Networks Networks - Intranet • This is a network that allows a private connection access to Internet services. This usually happens within a particular company or organisation. Authorised users only are allowed to access these services and this makes the network relatively secure. It allows secure email communication and the distribution of information similar to the World Wide Web.

7. Higher Grade Computing Studies5. Networks Networks - Intranet

8. Higher Grade Computing Studies5. Networks Networks - Internet • This is the most common example of a WAN. It uses telecommunications to transfer data between computers and distribute information. The World Wide Web (WWW) is a collection of information held on the Internet. The WWW is made up of millions of documents called web pages and these pages are available to any user of the Internet.

9. Higher Grade Computing Studies5. Networks Networks - Internet

10. Higher Grade Computing Studies5. Networks Mainframe Computer • A mainframe computer system has very fast powerful multiple processors, large fast memory and backing storage systems and the ability to support many network terminals at the same time. • Terminals usually consist of a keyboard and monitor only and rely on the mainframe to carry out all the processing and backing storage required.

11. Higher Grade Computing Studies5. Networks Network of Computers • Most computer networks have stations (computers) that can work efficiently on their own without the aid of a mainframe. These networks usually consist of desktop computers being linked together.

12. Higher Grade Computing Studies5. Networks Client Server Networks • Servers are powerful computers used to carry out various tasks across the network. Clients are computers that form the network.The user logs in to the server from the clients (username and password) and is permitted access to some resources on the network and denied access to others. • Servers can have a variety of functions ....

13. Higher Grade Computing Studies5. Networks Client Server Networks • File server • This provides a central disk storage area for any users across the network. The file server stores users files separately. Users can then access their files from any workstation on the network. • Web server • A computer connected to the Internet that stores and distributes Web pages upon request to users on the network. The "server" is actually a software program running on the computer .

14. Higher Grade Computing Studies5. Networks Client Server Networks • Print server • This computer allows the management of printing across the network. It uses a spooler to store users' files and can provide a queuing facility with prioritising if necessary. • CD-ROM server • This server allows all workstations across the network to obtain data from CD-ROM disks.

15. Higher Grade Computing Studies5. Networks Client Server Networks

16. Higher Grade Computing Studies5. Networks Peer-to-Peer Network • In a peer-to-peer network there are no dedicated servers among the computers. All of the computers on the network handle security and administration for themselves. The users must make the decisions about who gets access to what.

17. Higher Grade Computing Studies5. Networks Peer-to-Peer Network • Security on a peer-to-peer network is not very powerful. So if you have security concerns go for something you can control (like a server). Because the users will be required to give access to folders, they can choose to not require passwords.

18. Higher Grade Computing Studies5. Networks Peer-to-Peer Network

19. Higher Grade Computing Studies5. Networks Network Topology • The design of a network is called its topology. • A node is any device on the network, e.g. workstation (computer), server, printer. • A channel is the path over which the data is transmitted between computers, e.g. telecommunications links, wireless connection, fibre-optics or twisted pair copper cables.

20. = Node = Channel Higher Grade Computing Studies 5. Networks Network Topology • Mesh • Ring • Bus • Star

21. Higher Grade Computing Studies 5. Networks Network Topology TYPE OF NETWORK AFFECT ON PERFORMANCE ADVANTAGE DISADVANTAGE Mesh • Fault in one channel doesn't affect network - messages re-routed. • Lots of wiring. • Excellent performance • Multiple transmissions can occur at the same time. • Expensive

22. Higher Grade Computing Studies 5. Networks Network Topology TYPE OF NETWORK AFFECT ON PERFORMANCE ADVANTAGE DISADVANTAGE Star • Short path between any 2 nodes. • Fault in the central node means network is unusable. • Control computer gives more robust network but slows down communication between nodes • Easy expansion. • Congestion at central node.

23. Higher Grade Computing Studies 5. Networks Network Topology TYPE OF NETWORK AFFECT ON PERFORMANCE ADVANTAGE DISADVANTAGE Bus • Fault in one station has no effect on rest of network. • All stations use the same channel - each station has to compete for the central channel. • Central channel breaks – network fails. • Instant access but high rate of data crash. • Very easy to expand. • Cheap

24. Higher Grade Computing Studies 5. Networks Network Topology TYPE OF NETWORK AFFECT ON PERFORMANCE ADVANTAGE DISADVANTAGE Ring • Control system in charge of transmissions. • Additional expense for control software and system. • Network down to add new station but thereafter, few if any data crashes. • Stations guaranteed access to transmissions. • May have to wait to transmit.