1. Computer communication
Networks

2. Specification Requirements
Candidates should be able to:
describe the hardware needed to connect stand-alone computers into a local area network, including hub/switches, wireless access points
explain the different roles of computers in a client-server and a peer-to-peer network
describe, using diagrams or otherwise, the ring, bus and star network topologies

3. Network Hardware Network interface card:
A network adapter such as a network interface card (NIC) is needed to connect computers and other peripherals to a network, either by cable or wirelessly. Each connected device is allocated an IP address to uniquely identify it on a TCP/IP network.

4. Network Hardware Terminator Device attached to the end of bus network
Prevents signals from bouncing

5. Network Hardware Repeaters
Signals can lost integrity, become attenuated over long distances
Repeaters clean the signal up, then sends it on.

6. Network Hardware Hubs Effectively repeaters
Sends signal to all devices connected to it
Only intended receiver will process it
Used in star networks
Not good for large networks – collisions
Whole network goes down if Hub is broken

7. Network Hardware Bridges Connects different network segments together
Can speed up a networks performance
Only sends on to different segments, determined by reading MAC address
If not different segment then packet is discarded clearing up traffic.

8. Network Hardware Switches High Speed Bridge Has a dedicated CPU
Intelligently determines route of packet to destination

9. Network Hardware Twisted pair Cables
are the most common and is often called Ethernet cabling. Category 5 (Cat5) twisted-pair cables can carry 100Mb per second over distances of up to 100 metres.

10. Network Hardware Coaxial cable
is better at resisting electrical interference so it can be installed over longer lengths, but it is not as flexible.

11. Network Hardware Fibre Optic Cable
has a central glass core and transmits signals using light at extremely high speeds over huge distances. It can be used outside buildings but it is significantly more expensive to purchase and install.

12. Network Types Client Server
On a client-server network there are two types of computers with two distinct roles. One or more server computers have the role of controlling access to shared resources like files and printers. Multiple client computers are then connected to the server computers and these are where the user works.
The user typically logs onto a client computer which then connects to the server, verifies the user and then allows them access to the files and software stored on the server that they have permission to access.
All the data is stored on the servers, which generally have far greater security controls than the client computers. Since data storage is centralised, security is easier to manage, updates to the data are far easier to administer and it is far easier to backup the data centrally.
Some servers may have a more specialised role such as a print server, dedicated to controlling access to shared printers on the network and queuing print jobs in the order that they were sent by the users.

13. Network Types Peer to Peer
In a peer-to-peer network computers are simply linked together, either using cables and a hub or wirelessly.
Such networks do not have computers with particular roles, instead, each computer can simultaneously act as both a client and a server, and each has equivalent responsibilities and status.
This means that any computer on the network can load information from the hard disk of any other computer and a computer on the network can use any printer connected to any other computer.
A peer-to-peer network will be cheaper to set up and, provided there are only a small number of computers, will be easier to manage than server based networks.
However they are less secure and peer-to-peer networks are used mainly by home users and small companies who do not have the necessary technical staff to maintain a client-server network.

14. Network Types Peer to Peer Vs Client Server Peer to Peer Client Server
No network wide security
Central control of security.
Soon become unworkable
Easier to supervise network performance
Machines slow down when being accessed by others
Easier to perform software upgrades
Machines holding data being accessed can be restarted
Faster performance – fewer data collisions
Difficult to keep track of who has what information
Client machines freed up
Backup becomes complicated
Easier to perform back-ups
Expensive to set up and good expertise required
Infrastructure may be required.
Server failures have more impact

15. Network Hardware Servers Application Servers Communication Servers
DBMS Systems and other software
Communication Servers
Entry point to network for external users
File and Print Servers
Stores of data and access to printers
Mail Servers
Access to .
Web servers
Allows intranets
Contains devices such as webcams, routers etc.