The 6 Main Components of a Network
When a data packet is given to the router, it first reads the packet's destination address, then looks up all the paths it has available to connect to that address, and chooses the least congested one. The router then sends the data packet along that route.
If the data packet destination is outside the local network, then the router will send the packet to the internet modem. It is then sent to the internet service provider's router, which forwards the packet to it's address. This will send the data to many routers around the world before it eventually gets to it's destination.
Routers can also filter traffic and exchange protocol information across networks.
Network switches also stop data collisions (Data colliding on the same line) from occurring. If a data collision is detected, the switch sends the data back to the computers and makes them resend it at a different time to avoid data collision. However, on networks with many, many computers, this can slow down the network severely.
Because every computer encounters every data packet, security can be an issue. Say one computer downloads a virus infected piece of data. The data then goes on to the hub, which then could possibly transmit the virus to every other computer on the network.
Hubs are useful for small home networks, but for large business networks, security and network slowdown is too much of an issue. These larger networks usually use switches.
Servers usually have very large hard drives to store all the data they will need to be sending out to the network's computers. If a server gets infected with a virus however, the virus could be sent out to any computer that requests data from the server computer. This means that security on server computers is paramount.
Each NIC has a 48 bit identification code - its MAC address. The NIC card will only allow the data packet through if the network card sees that the destination address within the data packet matches it's MAC address.
MAC addresses can also be used to only allow certain computers onto a network. Any other computers are just ignored by the network.
Wireless Network Cards can also be used - these allow data packets to be transferred wirelessly.
Transmission of data is simple because data only travels in one direction, and there are no data collisions. Extra computers can be added without much trouble. However, because data has to pass through many other computers before reaching it's destination, these networks can be slow, and if a single cable or computer breaks, the whole network doesn't work. There can also be problems with security, because data has to pass through many other computers before reaching it's destination.
Ring networks are used in some offices and schools.
They are very reliable, because if a computer breaks, or a single cable breaks, the whole network carries on, but the computer that is unconnected cannot connect to the server. There are very few data collisions and excellent security as no computer can connect to another one other than through the server.
These networks, however, are very expensive to create, need extra hardware such as hubs and switches, and usually need professional help to set up. Also, if the server crashes, no computers will be able to access their data.
These networks are the choice for most schools and offices because of high security and reliability.
These networks are easy to install, are cheap, and you can add other components to the network easily. They are also cheaper than other networks, because they use less cable.
However, any problem with the central cable and the entire network goes down. These networks can also be quite slow if there are multiple computers on the network. Data collisions can be common if the network is busy, security is poor because all computers can see all the data on the network, and there is a maximum number of computers that can be installed due to cable length limitation.
These networks are often used for temporary networks and home LAN networks.
You usually need a user name and password to log onto a LAN network. This is so the server can recognise that you are part of the server.
An example of a WAN is the internet, the largest WAN ever.