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3.5 Internet protocol (IP)

At the time of writing (2002), two versions of IP are available: versions 4 and 6. In this section I shall describe version 4, which is abbreviated to IPv4, as it is the more widely available version. Version 6 may eventually replace version 4 because it has some additional features that may prove essential for multiservice networks.

IPv4 is the main TCP/IP protocol in the internetwork layer of the TCP/IP reference model. It supports a connectionless service between hosts in an interne
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2.3 Horizontal communication

In the OSI reference model there is a clear separation of services and protocols, but this separation is not always evident in practical applications, so it is worthwhile spending some more time on the differences between them. A service is provided by one layer to the layer above, and the capabilities of a service are defined in terms of primitives and their parameters. A service relates to two adjacent layers in the same system. In contrast, a protocol defines the communication between two
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Learning outcomes

After studying this unit you should be able to:

  • evaluate technical descriptions of communication protocols and demonstrate your understanding of their operation;

  • describe the characteristics of circuit-switched and packet-switched networks, and of connectionless and connection-oriented modes in packet-switched networks;

  • describe the role played by primitives in the OSI reference model;

  • explain how ‘vertical’ and ‘horizontal’
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5.5.5 Summary

In this section I've briefly considered the very contentious question of what digital representations mean, but this debate must be left to another course. I have also described some of the devices that take digital information back into the analogue world of sight and sound, presenting it in a form that is meaningful to human eyes and ears.


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4.4 Representing sound

Sound, such as speech or music, is an analogue physical quantity that varies with time, and so the ideas you have already met in Section 2.5 about converting analogue weights to digital form are relevant here too. In particular, samples of the sound will have to be taken, and each sample will have to be quantised to the nearest binary code in the digital representation.

It's important to appreciate that sound such as speech or music varies rapidly with time, and so samples of it will ha
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10.2 Ports

On the outside of a computer you will see a number of connection points that look like sockets. These sockets are known as ports and they provide connections between the computer and external devices such as a digital camera or printer. Ports control the flow of data between the computer and these devices, ensuring that data is sent and received quickly and reliably.

Modern ICT devices require increasingly large amounts of data to be sent between the computer and the devices. The
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10.1 Introduction

A stand-alone computer receives data from a user by means of input devices. The two most commonly used input devices are the keyboard and the mouse. A computer sends data to a user by means of output devices. Data may be output via devices such as a screen or a printer.

There are many different ways of getting data into a computer. For example, a scanner converts images and texts into a format that can be processed by the computer and displayed on screen. Devices such as t
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4.1.2 The network

The network is a communication channel in that it conveys data from the transmitter to the receiver. The network may also manipulate data in some way, and it may also store or retrieve data.

In a mobile phone system, the network conveys the message from User l's handset to User 2's. It will also store the identity of User 1 and the duration of the call. This data is used to work out the amount to charge User 1, which is a form of manipulation of data. A network can be very comple
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References

Eyewitness Travel Guide (1997) Amsterdam. London, Dorling Kindersley. pp. 120-1.
Götz, V. (1998) Color and Type for the Screen. Berlin, RotoVision (in collaboration with Grey Press).
Hartley, J. (1994) Designing Instructional Text. 3rd edn. London, Kogan Page.
Michaelis, P. R. and Wiggins, R. H. (1982) ‘A human
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4.1 Introduction

Section 2 explained that information is an important asset to an organisation. In this section you will study, in some detail, the characteristics of information assets that make them valuable, and so worth protecting.

In recent years, a combination of computerised processing systems and electronic communication technologies has made possible new forms of working and trading based on the electronic exchange of information. Such activity is called e-business or e-commerce.
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2.3 What is information security management?

Information security management is the process by which the value of each of an organisation's information assets is assessed and, if appropriate, protected on an ongoing basis. The information an organisation holds will be stored, used and transmitted using various media, some of which will be tangible – paper, for example – and some intangible – such as the ideas in employees' minds. Preserving the value of information is mainly a question of protecting the media in which it is
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4.1 Email attachments

Following some simple rules should help you to minimise the risks from malware. The first rule is:

  • Never ‘double click’ to open a file attached to an email

Instead, what you should do is:

  • Create a folder called ‘Attachments’ (or something similar) in an accessible location within your file structure. Mine is in ‘My Documents’ and is called ‘My Received Files’.


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4.3 Search

When you submit your query, the search engine will look up each word of the query in the index and construct a list of hits. Hits are pages that contain all of the words in your query.

If you perform an advanced search, additional filters are applied to the hit list. For example, if you search for documents in the .ac.uk domain only, pages from other domains will be excluded from the hit list.

Some search engines provide extra features. Most will check the spelling of the words yo
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6.6 ZigBee

Development of the ZigBee standard is the result of a group of interested parties coming together to form the ZigBee Alliance. When approved it will be an open standard sitting within a subset of the IEEE 802.15.4 low-data wireless standard. At the outset ZigBee was designed specifically for networks set up for the purposes of monitoring and control. Two of the major development aims were that it should be low cost (so that it is cheap to install and maintain), and low power (for long battery
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6.2 Devices in the home

Activity 24: exploratory

Take a mental ‘walkthrough’ of a typical morning in your own home, making a note of all the events and activities that involve electrical devices!


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5.6 Reliability and usability

In this context we will define reliability as the ability of a technology to perform its intended function, without failure, under stated conditions and for a stated period of time. It is beyond the scope of this unit to provide a detailed comparison of the reliability of WiFi and Bluetooth – we simply want to alert you to some of the issues. Broadly these are:

  • What is the likelihood of data errors being introduced during transmission?


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1.1 Getting an overview

This section starts with an article from a technical journal – the sort that is read by academics and professionals working in a related technical field. It sets the scene for some of the technologies and issues that you will be encountering later in this unit.

We're not going to ask you to read the entire article, but we would like you to get an idea of the article's contents, the kind of points the author is making, and the range of issues that it throws up. With this aim in mind, w
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Acknowledgements

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Figure 1 ENIAC Computer. Photo © Science Photo Library

Rozin, D. ‘Wooden Mirror’, 2001, IEEE Spectrum, March 2001, p.29. Co
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8 Online shopping – what it means

Shopping online is already very big business, and is growing rapidly. This suggests that the concerns of consumers discussed earlier are being addressed by the industry. People wouldn't shop online if they didn't trust it. But in a way the most profound impact of online retailing is being experienced in the ‘real’ world. According to the Economist magazine, for example, the Internet is profoundly changing consumer behaviour in the real world.

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7 What's going on with online shopping

Most e-commerce sites are designed to mimic as far as possible the process of shopping in real life – find store, locate goods, go to checkout, pay. The only difference is that you cannot take the goods away with you, but have to wait for them to be delivered by post or courier. (Even then, there are parallels in real life – for example, when I buy a washing machine or a fridge from a department store, I do not expect to take it home with me; instead I pay and make arrangements to have th
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