Networks Unit 3
Disadvantages of a network
Advantages of a network:
Share peripherals such as printer
Share software
Share data/files
Easier for internal communication/can send an email
Centralised backup
Easier to monitor network activity
Centralised maintenance (manage the network from one location)
Can acces data from any computer
A network manager may need to be employed - expensive
Security problems - files sent between computers could spread a virus
Hackers can gain access to data more easily.
If the server is down, all workstations on the network are affected.
Initial costs of servers, communication devices, etc can be expensive
LAN and WAN
There are two main categories of network - local area network (LAN) and Wide Area Network (LAN)
A WAN is a network in which the computers systyems are all located distantly from each other, for example, in different buildings all over the county or in different countries. The internet is an example of a WAN. Many LANs could be linked using a WAN.
A LAN is a network in which computer systems are all located relatively close to each other, for example in the same building or on the same site such as school.
Bus
If the address does not match, the computer system ignores the packet. If the address of the computer system matches that contained in the packet, it processes the data.
Hardware
Switches - A switch analyses each packet of data and sends it to the computer it was intended for.
Hubs - A hub copies all packets of data to all devices on the network.
Routers - A router stores the addresses of computers on the network and transfers data between devices.
Gateways - A gateway joins together two networks that use different base protocols, e.g. links a LAN to WAN.
Bridge - A bridge joins together two networks that use the same base protocols, e.g. links LAN to LAN.
A network is a number of computer systems connected together.
As the packets arrive at each computer system, it checks the destination address contained in the packet to see if it matches its own.
The bus carries data packets along the cable.
The bus has terminators on each end, which are needed to close each end of the cable.
The computers (nodes) are connected to a single cable on which data can be sent, called the bus.
Ring
Star
Advantages
Good performance/fast network speed
Easy to set up
Easy to add more computer systems without taking the network down.
Minimal network collisions
Better security
Disadvantages
Expensive to install as more cable is required
Extra hardware required, such as a hub
Mesh
Each node relays data for the mesh network. All mesh nodes cooperate in the distribution of data in the network.
This is very reliable as it can 'self-heal' by reconfiguring around broken paths. This network is complex, expensive and difficult to set up. A large part of the network may be redundant
Each node connects to exactly two other nodes, providing a single pathway for signals through each node.