An introduction to computers and computer systems
An introduction to computers and computer systems

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1.1 An example network

The internet provides the backbone for worldwide communication. You will look specifically at the internet and the technology that makes it work in Section 2. The term internet derives from the fact that the internet is itself made up of many other joined-together networks. But the internet is not the only player in providing communication. For example, there are the suppliers of broadband, the internet service providers, mobile phone operators, Wi-Fi access points and local area networks at work, to name most of the important ones. It is the joining together of all these different networks belonging to these service providers that allows us to access our workplace or browse the web seamlessly – that is, without being aware of the underlying networks that support the service.

Case study: A home office set up

Figure 1 shows one possible representation of the joining together of networks. In this example, a home network, a campus network and a branch office network are all joined together using the internet.

This is a diagram showing a home-to-office network: Home - Internet - University LAN - Branch office LAN.
Figure 1 Home-to-office network.

This is a representation of my own home-to-workplace set-up. At home, I have a laptop and iPad which both connect to my home hub using Wi‑Fi. My printer is plugged into the hub using an Ethernet port. The hub was provided to me as part of my contract with my broadband supplier and connects from my home to fibre-optic broadband. My broadband link will eventually get me to my internet service provider (ISP), where I will be connected to the internet through a router, called a gateway router in this location as it acts a gateway between two networks – in this case, the ISP and the internet. A connection is established across the internet to get me to another gateway router at the edge of the Open University network.

In this example, I wish to access a server at my office, which is shown at the bottom of the diagram. I have to pass through a hierarchy of network devices (routers and switches) to reach the server as the OU network supports over 3000 staff and many thousands of students. I would follow a similar pathway if I wanted to exchange emails with a colleague. Connections can be made in a similar way to a branch office. At both the University and the branch office, the collection of networking equipment is joined together using a Local Area Network (LAN). As an alternative to using the internet, the part in the middle of the diagram, which connects the university to the regional office, can be provided over privately leased links, when it then is referred to as a Wide Area Network (WAN).

In summary, my connection from home to office (university) has been made possible by joining together my home network, a WAN and a LAN: a network of networks.

Now you’ll look in more detail at these technologies.

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