NETWORKS

The 6 Main Components of a Network

1. Router

This component sends data packets to and from networks in the fastest and most efficient way possible. It can be used to transfer data from a computer to the internet, and from the internet to a computer. Routers have a micro-computer inside them, storing a "Routing Table" - a table that holds a list of all the networks it is connected to. It also holds how busy each network is at that moment.


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.


2. Switch

A network switch links network segments or network devices together. It receives data from one network device and then sends it on only to the device that the data was meant for, unlike the hub (see item 3), which sends the data on to all the devices on the network. It is very important for LAN (Local Area Networks) 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.

3. Hub

A hub connects all the computers on a network together, allowing them to send data packets to each other. When data arrives at a hub, it transmits the data to every other port (the computer connection site) on the hub. It doesn't examine data packets like the switch, so data collision is much more frequent and much more of a problem.


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.

4. Server

Servers are computers that serve the needs of all the other computers on a network. This could be for sending out files and storing them, for storing databases, or for gaming.


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.

5. Client

Network clients are the computers that data is "Served" to. These are usually personal desktops or laptops that are used by people on the network.

6. NIC

Network Interface Cards (NICs) are inserted into a computer if it does not have a network chip on the motherboard. It allows data packets to be transferred to and from the computer.


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.

RING NETWORKS

Ring networks are where all computers in a network are connected in a circle. Data passes through the other computers in order to reach it's destination, a bit like a game of pass the parcel.


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.

STAR NETWORKS

In a star network, all computers are connected to the server directly by it's own cable.


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.

BUS NETWORKS

Bus networks are the simplest of all networks to create, because only a single cable joins all computers and other components of the network together. Two signal terminators sit at the ends of the network to stop data bouncing back.


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.

LAN NETWORKS

When computers close to each other are connected either by cables or wireless technologies, then they form a LAN network (Local Area Network). These computers can then share data, peripherals and software quickly at the same time.


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.

WAN NETWORKS

WAN networks (Wide Area Networks) are used to transmit data between computers situated far away from each other. For example, a large company has offices all over the world that need to communicate with each other. They would use a WAN to let employees access the same data wherever they are. WAN Networks connect multiple smaller LAN Networks together over long distances, usually using a telephone system or a modem. They can also be connected by fibre-optic cables or sattelites.

An example of a WAN is the internet, the largest WAN ever.

DIFFERENCES BETWEEN LAN AND WAN NETWORKS (using examples)

LAN networks are local to a certain area, so a home network where all peripherals are connected to the computers, and all computers are connected to each other would be a LAN network, even if it had a modem connecting it to the internet. WAN networks are much bigger (geographically speaking), and so an example of a WAN network would be the connection of company offices across the world.