Types of computer networks

There are two main type of network:

• Local Area Network (LAN) - E.g. your home network or the school network (covers a small area such as a school, home or office)

• Wide Area Network (WAN) - E.g. The Internet (covers countries and continents)

• A LAN covers a small area such as a single room or a building and is usually owned by an individual or single company.
• The school has a LAN that connects all of the computers within it together and on to a bigger network.

• A WAN covers a much larger area than a LAN. For example, a WAN may cover a whole country (e.g. BT or Sky Broadband) or a whole continent.
• The Internet is an example of a WAN.
• WANs are often made up of smaller LANs.

Advantages of LANs:

• Allows sharing of expensive hardware
• Allows fast transmission of files
• Allows for reliable transfer of files
• Allows computers to share one Internet connection

Advantages of WANs:

• Allows data and files to be shared around the world
• Allows users to remotely access their computers
• Allows services such as ATMs (cash machines) to be connected directly to the bank’s network and accessed anywhere
• Allows companies who are in different countries or continents to communicate as if they were in the same building

A server is a special computer designed to carry out one specific job for another computer. There are several types of server including:

• A file server is used as a central file storage. Users are given specific rights (such as read and write) to certain parts of the file server.
• A print server is used to share a printer on the network
• A mail server is used to send and receive emails
• An application server is one that allows applications to be stored once on a server and then loaded on to the client computer's RAM when it is needed
• Web servers are connected to the Internet and are used to host web and deliver webpages and files that can be accessed from any computer using a web browser.

• At the centre of a client-server network is a server that is responsible for allocation of resources and all nodes connect to it.

• The client(s) access resources that the server manages and provides users with access to these resources

• In a peer-to-peer network each computer has it's own resources and security settings.

• Each computer is either directly (through a cable from each computer to the next and back) or indirectly (through many network hubs or switches) connected to each other.

Client-server advantages:

• One central file storage means that it is easier to set access rights to files and to back up the files

• The same files can be accessed from any computer

Client-server disadvantages:

• Cost – initial set up is expensive

• Requires someone to manage the server

Peer-to-peer advantages:

• Easy setup: most computers are ready to go out of the box

• Cheap to setup: you need a few computers and cables and you’re good to go

Peer-to-peer disadvantages:

• Backups are difficult because files are stored on different computers across the network

• Security of files is not easy to enforce since it is not in a single central location

• There are several types of networking devices, each with its own specific purpose within a network topology. The following devices are used to make up a network:
  • Hub
  • Switch
  • Router

• A hub is a very basic device that allows multiple users to share one connection. 
• Any data sent to a hub is distributed to all devices on the hub. It's then up to each device to figure out if it was meant for them. 
• Hubs are very simple to build but also very slow compared with the more advanced switch.

• A switch is a more advanced version of a hub whereby the ports are given the full bandwidth of the network connection they are connected to.
• They achieve this by using a technique known as polling where they move through each port on the switch very quickly and gives the full bandwidth of the port for a short period then moves on.
• Each device only receives the data it requested with a switch.

• Routers are used to connect multiple networks together. For example, your home router will connect your home network (often built-in to the router too) to the Internet.
• Routers are very common now, but back in the early 2000s most people had one connection to the Internet through a modem.

• There are four common topologies that describe how networks are organised.
• Most of us use a star topology.
• If you're interested in these words, feel free to look them up.