June 2010 Edition
Computer Science Department, University of Cape Town
| MSc-IT Study Material June 2010 Edition Computer Science Department, University of Cape Town |
Although many Web designers may never set up a local area network (LAN), some background knowledge is essential to understand the protocols explained later in this unit.
Firstly, a definition of a LAN:
' a communications network that interconnects a variety of devices and provides a means for information exchange among those devices' - (Stallings, Data and Computer Communications, 1997)
This definition does not provide a clear distinction between WANs and LANs. There are several key differences that need to be mentioned:
LANs are usually owned by the same organisation.
The area covered by a LAN typically spans only hundreds of metres, rather than hundreds of kilometres, which is the case for a WAN.
Typically, a LAN is no larger than an office floor. Such a relatively small size leads to different technical solutions.
Because the area covered by a LAN is so much smaller, the technology to transmit data is substantially different from that of switching techniques.
LANs use broadcasting strategies. Broadcasting strategies transmit data from the source device to all other receiving devices connected to the LAN. Although Web designers do not need to understand these strategies, they should be aware of this distinctive nature of LANs.
Read up about LANs in your textbooks and the Internet. You should focus on LANs as carriers of multimedia applications.
Do Review Question 2
We now describe the infrastructure of the Internet. This will be done by first defining the simplest components of the Internet, and from there working towards the larger components. Remember that the Internet is a network of networks. It is the largest, and most successful, example of internetworking. This term is used by some suppliers of network technologies to capture all the concepts, technologies and devices that allow computers to communicate between different networks. This is typical of the Internet. By extension, an internetwork is simply a collection of networks that are connected together by intermediate devices to create a single, larger network.
A simplified diagram of such a construction is shown in the figure below, which shows an internetwork architecture using WANs and LANs.
The simplest component on an internetwork is a user device, typically a computer terminal.
In order for devices from different LANs located in different geographical locations to communicate, it is necessary to construct a WAN.
We now turn to the protocols used in the biggest internetwork, the Internet.