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Information Systems The Internet Unit

[HIGHER] Bruce Kerr

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The Scottish Qualifications Authority regularly reviews the arrangements for National Qualifications. Users of all NQ support materials, whether published by LT Scotland or others, are reminded that it is their responsibility to check that the support materials correspond to the requirements of the current arrangements.

Acknowledgement Learning and Teaching Scotland gratefully acknowledge this contribution to the National Qualifications support programme for Information Systems. First published 2005 Š Learning and Teaching Scotland 2005 This publication may be reproduced in whole or in part for educational purposes by educational establishments in Scotland provided that no profit accrues at any stage. ISBN 1 84399 031 8

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CONTENTS

5

Tutor notes Section 1:

Introduction

11

Section 2:

Internet services and resources

13

Section 3:

Technical issues

25

Section 4:

Regulating the Internet

47

Section 5:

Internet security

55

Section 6:

Policing the Internet

71

Section 7:

Introducing HTML

79

Section 8:

HTML design elements

89

Section 9:

Website design

107

Section 10: Uploading and publishing web pages

121

Section 11: Client-side scripting

125

Section 12: Server-side scripting

141

Section 13: Cascading style sheets

143

Section 14: Practical task and checklist Outcome 2 Observation checklist

155 159

Appendix:

161

HTML tags

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TUTOR NOTES

About this pack The materials in this pack cover: • Internet (theory) • HTML. Sections are included on: • creating a multi-page website • observation checklist for Outcome 2. The materials covering Internet (theory) and HTML contain a number of student-based tasks. Internet (theory) deals with such matters as TCP/IP and IP addressing, while HTML looks at all aspects of creating an interactive website. In Section 2, students gain knowledge and understanding about the development of the Internet and the services that are supported by it. The list of Internet services includes: • • • • •

World Wide Web (WWW) e-mail conferencing and newsgroups file transfer and file updating chat/instant messaging.

The WWW can be used for: • • • • • • • • •

education shopping booking holidays booking flights banking advertising 24-hour news interactive gaming virtual reality.

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TUTOR NOTES

In Section 3, students gain knowledge and understanding about the transmission hardware that is used by the Internet. Students gain knowledge about the specific use of, e.g. routers, multiplexors and gateways. Students gain some understanding of the structure of URLs, including: • • • • •

protocol domain name path file identifier port number (optional).

Students are required to carry out a number of practical tasks, which will illustate the dynamic nature of the Internet. These tasks require access to the C:> prompt, which will allow students to PING and ROUTE and TRACERT (trace route). These tasks may be difficult to carry out on a school computer system, but students should be encouraged to try. The information supplied by these utilities will give breadth to the topic. Protocols and IP address classifications are used to transmit information between networks. This section looks at TCP/IP transmission protocol and packet switching, and how IP addresses contain information about the network ID and the host ID. The notes explain IP address structure and classification in some detail. This section then looks at sub-netting. In Section 4, students examine the main Internet regulatory bodies and gain an understanding about how they function and what they try to regulate. Students will use advanced searches to investigate top-level domain names and generic domain names. In Section 5, students gain an understanding about the need for virus protection and the need to keep virus protection software up to date. Internet security also covers the use of firewalls, proxy servers and packet filtering routers, and how filters are allocated. This section also looks at: • • • •

encryption key distribution problem RSA public and private keys

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TUTOR NOTES

• PGP • secure sockets. Asymmetric mathematics and one-way functions are looked at; this is required for completeness. Students may find the maths difficult to follow; all that matters is that students gain an understanding of the principles and processes involved. Students are also required to establish their browser software encryption security level. Section 6 covers UK laws and how the Internet affects these laws. Students gain understanding about the collection of information via the Internet, which uses methods like submission forms and visitor books. Is the information gathered covered by UK laws? The Data Protection Act is looked at, and how it attempts to deal with Internet users who gather and process information over the Internet. Students are encouraged to look up open websites to see the personal information that is accessible on the Internet. Section 7 looks at HTML script, client-side script and cascading style sheets. Students can only gain a flavour of these topics; each requires a 40-hour course in its own right. Students should gain knowledge and understanding about the need for and use of scripting and style sheets on the WWW. The HTML notes give students an understanding about headers, meta data, scripts, styles and body. In Section 8, students are required to create HTML scripts that will: • • • • • • • • • • •

hyperlink use headings <h1> … <h6> change fonts use RGB colour structure use colours set background colours change link colours create tables insert table data insert graphics allow meta data.

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TUTOR NOTES

In Sections 9 and 10, students gain knowledge and understanding about web page design, uploading websites to web servers, and the need to use ‘index’ to publish websites. Web page layout has to be flexible. Headers should be used for graphical impact and navigation links. Footers should contain copyright information and, in the case of a long web page, a means of navigating to the top of the page. The left margin may contain menu options. The gutter margin should be left blank, as it breaks up the margin area and the content area. The content area contains the web page information. It is important to remember that the line length should be easily readable – that is, without undue movement of the human eye. Students should be discouraged from using horizontal scroll bars as Internet users find it difficult to cope with, and hard copy print-outs are useless. In Section 11, students gain knowledge and understanding about the need for client-side scripting. The scripted code is contained within the web page and is executed once the web page has been downloaded. Students will use JavaScript and VBScript. Most school computer systems have access to Visual Basic; students will have little difficulty using VBScript. JavaScript may need the implementation of Java Console, which might be difficult on a school computer system. If Java Console cannot be implemented, then teachers should concentrate on the VBScript tasks. Document Write and Document Cookie routines are used to demonstrate dynamic website construction. Students should be aware that HTML, on its own, cannot create the dynamic web pages that they have been using on the WWW. In Section 12, students are required to produce submission forms and gain knowledge and understanding about the need to validate data before the data is sent to the web server for processing and storage in a MySQL relational database. Students will use Alert messages, or Messagebox messages, to display messages about data transfer or to show that an error has occurred. Submission forms need client-side scripting to send collected data to the web server’s cgi bin. Web-side scripts, such as PHP, are used to preprocess the data before transmitting a reply to the user. Students will gain an understanding of the use of PHP on the Internet.

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TUTOR NOTES

In Section 13, students discover how cascading style sheets are used to set up a standard style format for a number of different web pages. Students will gain knowledge and understanding about the need for and implementation of cascading style sheets. Students will be required to write cascading style sheets and implement the style sheets in their own web pages. In Section 14, a practical task is described, which covers the skills laid down for Outcome 2. Teachers can instead produce their own tasks to demonstrate the Outcome. An observation checklist for Outcome 2 is supplied at the end of the materials. PowerPoint presentation A PowerPoint presentation linked to this pack may be downloaded from the Information Systems subject pages in the e-library at www.LTScotland.org.uk/NQ

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INTRODUCTION

SECTION 1

The Internet The Internet is a network of interconnected networks. It allows worldwide communication and the distribution of information, and is the worldâ&#x20AC;&#x2122;s largest network. In order to work, the Internet needs to overcome the problems of different connected networks, running on different types of computer hardware and using different software applications. The Internet uses communication protocols to overcome these problems. Internet development Timothy Berners-Lee created the original HyperText Transfer Protocol (HTTP) and HyperText Mark-up Language (HTML), which allowed users to share information over the networks, using a document viewer or browser application. The document viewer could parse the HTML script; that is, it could scan through the script, interpreting and executing all HTML commands, or tags, while ignoring the basic text. The original HTML only allowed the transmission and viewing of text documents. In the early 1990s, HTML was a basic language predominately used to display abstracts from research documents. HTML was well defined and well structured, containing a paragraph structure and a few features that could be used to break up the document. Mosaic was the first browser application to allow graphics. Mosaic embedded graphics into an HTML document by using a hyperlink image reference, which pointed to the original image file on the server. With Mosaic, anyone could place images into a document. Users with no specialisation in computing and who had no HTML training began to display information on the Internet. These users included graphics in their web pages and also used graphics as navigation aids, such as image maps.

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INTRODUCTION

Netscape began to introduce new elements into HTML, such as emphasis and strong. These elements were later called bold and italic. Microsoft entered the market in 1995 with its own browser application software. Netscape and Microsoft began submitting new tags for approval on a regular basis. Unfortunately, some of these were totally useless! The <table> tag, which allows authors to place content into a table structure, was a disaster, with Netscape and Microsoft using different definitions. This meant that an author would need to produce two different tables, one for Netscape and the other for Microsoft browsers. Many authors depended upon client-side scripting to investigate which type of browser was being used and then direct the web page to an appropriate set of table definitions. Netscape countered with <frame>, which divided the browser window into separate frames. Navigation between the frames caused difficulty and web authors had to direct output to particular frames. Font elements were now being introduced and the author could <span> the text and set up font styles and colours. In 1998, Microsoft launched the Windows 98 operating system, which came with a free Internet browser. After much legal tussle, this was the final blow for Netscape and in 1999, America Online and Sun Microsystems acquired the Netscape business. Today Microsoft Internet Explorer is the most popular of all the web browser software, being used by the majority of PC users.

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INTERNET SERVICES AND RESOURCES

SECTION 2

Internet services The Internet offers users a number of services: • • • • •

World Wide Web (WWW) e-mail conferencing and newsgroups file transfer and file updating chat/instant messaging.

World Wide Web The World Wide Web is the most commonly used Internet service. The WWW consists of millions of multimedia hyperlinked documents. Each multimedia document is a web page. A website consists of a number of hyperlinked web pages. Web servers store thousands of websites and are operated by Internet Service Providers (ISPs) among other organisations. An Internet user needs browser software to download and interact with web pages. The web server sends a copy of the web page instructions to the user’s browser. The browser software interprets these HTML instructions, displaying the web page in the browser. A browser is capable of displaying many different media – text, graphics, video, etc. The WWW has many uses, including: • • • • • • • •

education shopping booking holidays booking flights banking advertising 24-hour news web TV/radio

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INTERNET SERVICES AND RESOURCES

• interactive gaming • virtual reality. NB: many people call the Internet the World Wide Web. This is not accurate. The Internet is the interconnection of networks and the World Wide Web is an Internet service. E-mail E-mail allows users to send messages to one another. Each user has a mailbox into which e-mail is delivered. A mailbox is a Storage area on the ISP’s web server. E-mail software (e.g. Outlook Express) allows the user to create and send e-mail messages. The user can also attach files to an e-mail. An attachment can be any type of data file, ranging from word processing documents to graphics. Conferencing and newsgroups Conferencing allows three or more Internet users to take part in a realtime conference. Internet users can see each other and speak to one another real-time, using specialised video-conferencing software. Newsgroups are specialised message services. Most newsgroups are dedicated to a particular topic, like computing or sports. Internet users can subscribe to the newsgroup and read the messages that have been posted. The user can also leave or post messages. File transfer and file updating File transfer (FTP) software allows users to upload or download files, such as music, video, graphics, data and software. Companies, such as Microsoft, use FTP to automatically download software updates. Browser software now supports FTP, so there is no need to use specialised software to upload data files. Chat/instant messaging Chat allows Internet users to communicate interactively. Users can send and read real-time messages. Internet Relay Chat (IRC) allows many users to communicate over the Internet without any undue delay.

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INTERNET SERVICES AND RESOURCES

Task 1 Answer the following questions. 1. What exactly is the Internet? 2. List five Internet services. 3. Which service would you use if you wanted to play an interactive game? 4. How are web pages joined together? 5. What is contained in a website? 6. What is a mailbox? 7. What does e-mail software allow the user to do? 8. What is an attachment? 9. What is meant by real-time? 10. How do Internet users communicate when conferencing? 11. What does the chat service allow Internet users to do? 12. Explain the difference between the Internet and the WWW.

Internet resources There are three main types of Internet resource: • academic • commercial • personal. Academic There are a number of academic resources: • • • • • • •

edutainment e-books e-learning web-based training virtual libraries e-journals university, college and school websites.

Edutainment Edutainment is a resource that is both educational and entertaining. Edutainment websites allow students to learn while having fun.

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INTERNET SERVICES AND RESOURCES

E-books Books and textbooks available in an electronic format. Adobe’s Acrobat Reader uses a portable document format (PDF), which allows readers to view documents originated in any software. E-learning E-learning is learning using ICT, usually involving the Internet. E-leaning offers a number of benefits over conventional learning: • • • • • •

students do not need to travel to school or college courses are available 24-hours a day learning is interactive multimedia can make subjects more appealing students can use the Internet to exchange knowledge students can manage their own learning.

A good example of an e-learning website can be viewed at: www.bbc.co.uk/scotland/education/bitesize Web-based training Web-based training is a form of e-learning, more applicable to adult education or vocational training. Check out: www.syberworks.com

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INTERNET SERVICES AND RESOURCES

Virtual libraries The Internet is an information resource that brings information from all over the world to the userâ&#x20AC;&#x2122;s desktop. The growth in web-based database services has led to the development of virtual libraries.

Check out the following virtual libraries: www.royalsoc.ac.uk/library www.bl.uk E-journals E-journals are the electronic equivalents of printed scientific/academic journals.

Check out the following e-journal: www.thelancet.com

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INTERNET SERVICES AND RESOURCES

University, college and school websites All universities and colleges, and most schools, have websites providing information for staff, students and visitors. Check out: www.ed.ac.uk www.lauder.ac.uk Commercial There are many commercial resources, including: • • • • •

e-commerce e-banking airline reservations e-marketplace advertising.

E-commerce The Internet can be used to purchase just about anything. Ironically, the first Internet business was set up to sell books. E-commerce has many advantages for buyers and sellers alike: • sellers do not need large stores, nor do they need to employ a large number of staff • both have access to a worldwide market, open 24 hours a day, 365 days a year • customers are able to shop or browse and use services from the comfort of home • customers can gain impartial purchase advice and look around for the best prices. E-commerce also has many disadvantages for customers: • customers can only see pictures of the goods, and a text description • customers have to trust that an overseas company will send the correct purchased goods and give after-sales service • customers need to be sure that their credit card details will not be misused. The effects of e-commerce on society are far reaching. Old jobs are lost; new jobs are created.

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INTERNET SERVICES AND RESOURCES

One recent development is online auction sites, which allow private individuals to buy and sell goods in a secure environment. E-banks With Internet banking, customers can check their own accounts, pay bills and transfer money between accounts. As with e-commerce, this service is available 24-7-365, so there is no longer any pressing need to physically visit a bank. Airline reservations Ticket offices in airports and travel agencies are linked to computers that store flight details. Internet users can check these flight details themselves and book their flights direct. E-marketplace E-marketplaces are trading groups that allow businesses to speak to other businesses – B2B (business-to-business). Advertising Most Internet users are painfully aware of the pop-ups and banner ads advertising anything from credit cards to exotic holidays. However, the revenue raised by these advertisements keeps a lot of websites in business. Personal There are many types of personal resources on the Internet, including: • • • • • •

computer games multi-user games news and weather music and video distribution local information services personal websites.

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INTERNET SERVICES AND RESOURCES

Computer games and multi-user games The Internet has a feast of games and amusements. Multi-user games (MUGs) allow users from all over the world the chance to compete.

News and weather Most news agencies (e.g. BBC, CNN) have websites which carry up-tothe-minute news and weather. Music and video distribution The music and film industries use the Internet to sell records and DVDs. Media player software allows for easy searching and downloading of these resources.

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INTERNET SERVICES AND RESOURCES

Local information services The Internet can be used to get local information, e.g. what is on at the cinema, or what the latest traffic news is. Local directories (e.g. Yellow Pages) provide contact details for local services. Personal websites Many users create their own personal websites. These can be fun for the author, and can also be a source of useful information, e.g. local history.

Task 2 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

List three main types of Internet resources. What is meant by ‘edutainment’? Explain ‘e-books’. What advantages are offered by e-learning? Why might professionals find e-learning beneficial? What advantages has e-commerce given to companies? What advantages has e-commerce given to customers? What are the main disadvantages for customers? How has the Internet affected banking? Explain how the Internet has changed the airline reservations business. Why is advertising revenue important to the Internet? What are MUGs? What type of service is distributed on the Internet by news agencies? How could you use the Internet to find a plumber?

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INTERNET SERVICES AND RESOURCES

Web resource information Anyone can put content onto the Internet, so it is unwise to simply accept information uncritically. Any information should be assessed by the user for: • accuracy • bias • credibility. Accuracy When interacting with web resources the user must be aware that the information may or may not be correct. There is no quality control on the Internet. The information might be partially or entirely wrong, or totally out of date. Bias The Internet contains some information that is deliberately misleading and prejudiced and which states only one side of an argument, i.e. the one that the web author wants others to believe. But how can you tell if the contents of a web page are biased? Generally speaking, you will need to have some prior knowledge of the topic. So, you may need to do some studying before you access the website. Credibility The information on the Internet might or might not be believable. Web pages might contain information that is fiction, even when it claims to be true and accurate. It is important that Internet users are more than aware of these problems. Here are a few tips, which might help you gauge the reliability of information posted on a website. • • • •

Is the author’s name displayed on the site? Can the author be contacted? If not, why not? Is the author qualified; does he/she know anything about the subject? Is the site well laid out, up to date and error free? If not, can you really trust the information? • Are any reliable sites hyper-linked to the website in question?

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INTERNET SERVICES AND RESOURCES

• Is it an educational site? (.ac.uk or .edu) • Can the author be contacted by e-mail?

Task 3 Check out the following websites and assess them for accuracy, bias and credibility. URL www.cam.ac.uk/global/search www.statistics.gov.uk www.foodstandards.gov.uk www.fife.police.uk www.astrology.com www.timeshare-spain.tinusi.com www.weather.com www.geocities.com/theanticanadapage/ www.scottish.parliament.uk/ http://edition.cnn.com/2004/TRAVEL/07/ 17/bt.archieves.cnn/index.html www.skoda.co.uk www.carluke.com www.utexas.edu

1. 2. 3. 4. 5.

Accuracy Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No

Bias Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No

Credibility Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No

Yes/No Yes/No Yes/No Yes/No

Yes/No Yes/No Yes/No Yes/No

Yes/No Yes/No Yes/No Yes/No

Make a list of websites that you consider to be inaccurate. Make a list of websites that you consider to be biased. Make a list of websites that you consider to be unbelievable. Explain how you might be able to detect if a website is reliable. Write an essay outlining the need for Internet users to consider the accuracy, bias and credibility of websites and web pages.

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TECHNICAL ISSUES

SECTION 3

Hardware Server-side hardware can consist of: • • • • • • • • •

computers disk drives communication links multiplexor hubs switches routers gateways bridges.

Multiplexor A multiplexor allows a number of workstations to simultaneously gain access to the Internet using only one Internet communications link.

Communications channel

It receives data from a number of sources, and then splits the data into discrete blocks called packets and transmits them over the link. Intranets, which consist of a number of hosts, are linked to the Internet by a multiplexor.

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TECHNICAL ISSUES

Hubs Network hubs are multi-port devices, connecting the computers to the network. They are generally passive, simply allowing data to pass through. Data sent over the network is specifically addressed to a destination (by IP address). The hub ‘understands’ this information and sends the data onwards. The routing of the data over the network is by software command. Switch A switch is a multi-port hardware device that reads the destination address and physically switches the route between the source and destination. A store-and-forward switch can read a packet and check that the packet has been sent correctly, before forwarding it to its destination. Switches tend to be faster than hubs. Router The most important of all Internet devices are routers. Without routers we quite simply would not have the Internet. A router is a hardware device that will store and forward packets by checking IP addresses and then routing the packets to their destinations. A simple router is needed to link an Intranet to the Internet. The Internet requires the use of complex routers, which are switches that have access to routing tables. A routing table is a database, which contains all of the information about a network and the optimal paths or jumps between source and destination. Packets can be routed so that they take the shortest path to their destination.

2J

Router

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1 Ju

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Workstation

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Web Host


TECHNICAL ISSUES

Internet routers are dynamic, as they speak to one another, automatically updating their routing tables.

Task 4 Answer the following questions. 1. What is a multiplexor and what does it do? 2. What is a router and what does it do? 3. What are routing tables and what do they contain? 4. How are routing tables updated?

Uniform resource locator (URL) The Internet allows the user to locate different resources. The resource might be a piece of text, or an image or a means of booking a holiday. A resource is a file that is stored somewhere on the Internet. Every file needs a unique web address.

A URL is the unique web address of the resource, for example; • http://www.mywebsite.co.uk/internet/routers/tables.html • http://www.mywebsite.co.uk/internet/router/images/server.gif The first URL will locate a web page, while the second will locate an image. URL structure All URLs require the following elements in their structure: • • • •

protocol domain name path file identifier.

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TECHNICAL ISSUES

A protocol is an agreement or standard set of rules between two or more parties. Internet protocols ensure the successful transfer of data. There are transmission and service protocols. TCP/IP and IP addresses are transmission protocols; HTTP and POP/SMTP are service protocols. The URL http://www.mywebsite.co.uk/internet/routers/tables.html can be divided into each of the main elements: • • • •

protocol domain name path file identifier

http www.mywebsite.co.uk /internet/routers/ tables.html

The protocol HTTP uses communications channel (or port) 80 to receive World Wide Web documents. The port number may need to be altered if the resource is on an intranet or located using a proxy server. The URL below includes a port number: http://www.mywebsite.co.uk:8080/internet/routers/tables.html Summary • Standard URL structure: protocol ://domain name/path name/file identifier • URL structure with port number: protocol ://domain name :port number/path name/file identifier

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Task 5 Answer the following questions. 1. 2. 3. 4. 5.

What is a URL? List the types of resource that can be located on the Internet. List the five URL elements. Why might the port number need to be included in the URL? Identify the protocol, domain name, path and file identifier for each of the following URLs: (a) (b) (c) (d) (e) (f) (g)

http://www.mywebsite.co.uk/internet/routers/index.html http://www.mywebsite.sch.uk/geography/images/map.jpg http://www.mywebsite.com/sounds/midi files/bang.wav http://www.mywebsite.org.uk/classic /style /font.css http://members.lycos.co.uk/scotland/high lands/skye.jpg http://cnn.com/news/uk/scotland.html http://bbc.weather.co.uk/swscotland/ayrshire/arran.gif

Domain name server and IP address IP addresses The Internet connects millions of different network hardware components together. Each component is referred to as a host. The host is uniquely identified on the Internet by having a unique identification number – an Internet protocol (IP) address, which appears as a dotted decimal number, for example: 10.120.10.60 Each separate decimal number (in the range 0–255) is called an Octet. Each octet represents an 8-bit binary number. 10 00001010

120 01111000

10 00001010

60 001111000

If you know the IP address of a resource, you can enter it directly into the address bar in your browser window.

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TECHNICAL ISSUES

Domain name server (DNS) A domain name server resolves a web address into the correct IP address. If you entered the following web address – http://www.thisiseasy.com – into your web browser, how is it located? The simple answer is that it is not located: the web address needs to be resolved into the correct IP address (e.g. 205.23.12.27). The operating system compares the domain name with the domain name that is currently being referenced. If the names match, then the web page is displayed. If the names do not match, then a fully qualified domain name (FQDN) is requested from the DNS server. The DNS server holds a list of web addresses and their associated IP addresses. The DNS then passes the correct IP address to your computer and the connection is made. If the DNS cannot resolve the web address, then it contacts another DNS server and requests that the web address be resolved. If the web address cannot be resolved, a negative result is sent to your computer. You may have seen a 404 error popping up! Client to DNS to DNS resolution

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V

DNS

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205.23.12.27

DNS

V

http://www.thisiseasy.com

V

http://www.thisiseasy.com

DNS

DNS


TECHNICAL ISSUES

Task 6 Answer the following questions. 1. 2. 3. 4. 5.

What does a domain name server do? Explain how the web address http://www.thisiseasy.com is resolved. What is meant by FQDN? Explain what happens if the current domain name is not being referenced. Explain what happens if the domain name is not resolved by the DNS.

Timeouts Clearly, resolution cannot go on forever – it must be completed inside an acceptable period of time. After a minute or so, depending upon configuration, a timeout error will be generated. The web address resolution process will be terminated and an error will be generated. NB: You can bypass DNS by memorising all the IP addresses that you use! Error resolution There are various utilities that allow you to see what is going on behind the scenes. These include Ping, Route and NetStat. Ping This displays statistics about the number of ‘jumps’ needed to reach a particular website. Ping sends four packets to the destination address and returns the time needed to make the round trip from source to destination. Route This utility displays detailed information from the routing tables. NetStat Returns network statistics.

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TECHNICAL ISSUES

Task 7 Use the Command Prompt program to run the following network utilities: C:\>Ping www.yahoo.com C:\>Ping www.ask.com C:\>Route C:\>NetStat –a C:\>NetStat –p

Example screenshots from Ping and Route are shown below. These will help you make sense of what you see on your own screen. Study them if your computer doesn’t allow access to these programs. Ping

The Ping shown above displays the IP address – 216.109.118.69 – of www.yahoo.com. Ping displays the time needed to send the packets from router to router. This utility is very useful if you want to investigate if a website actually exists.

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TECHNICAL ISSUES

Route

Note that Route displays destination, mask, gateway addresses. You will learn more about gateways and network masks later in the Unit.

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TECHNICAL ISSUES

Transmission control protocol/Internet protocol (TCP/IP) TCP/IP is a set of protocols: • IP uses the IP address of both the source and the destination • TCP creates data blocks called packets, and packet numbers. Consider how a document would be sent from www.you.com to www.yahoo.com. Document TCP divides the message up into data blocks called packets. Packets Each packet is allocated a unique packet number, along with the total number of packets that will be sent. 1:5

2:5

3:5

4:5

5:5

IP is responsible for the delivery of each of the packets to the destination. IP now adds the source IP address and the destination IP addresses to each of the packets. Source IP Address

Destination IP Address

1:5

Source IP Address

Destination IP Address

2:5

Source IP Address

Destination IP Address

3:5

Source IP Address

Destination IP Address

4:5

Source IP Address

Destination IP Address

5:5

Each packet is now ready to be sent onto the Internet and make its own way to the destination address.

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Packet switching The Internet relies upon packet switching to transmit information from source to destination using TCP/IP. Different packets may follow different routes, as shown below. Step 1 129.23.27.4

Packet 2

Packet 1

10.10.8.10

Step 2 129.23.27.4 Packet 2

Packet 1

Packet 3

10.10.8.10

Step 3

129.23.27.4

Packet 2

Packet 1.5 Packet 3

Packet 5

10.10.8.10

Packet 4

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TECHNICAL ISSUES

Step 4 Packet 5

Packet 2 Packet 4

129.23.27.4 Packet 1.5 Packet 3.5

10.10.8.10

Step 5

Packet 5

129.23.27.4 Packet Packet Packet Packet

1.5 3.5 2.5 4.5

10.10.8.10

Eventually, all five packets will arrive at the destination. Since the packets took different routes through the Internet and passed through different routers, it is highly likely that the packets will arrive in a random order. The web server at the destination address needs to sort the packets into numerical order before the message can be read. The main advantage of using packet switching is that a telephone line or communications channel does not have to be totally devoted to linking a sender and receiver, unlike making a telephone call. With packet switching, a communications channel can be used to pass messages between many users.

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Task 8 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

What are protocols? What do Internet protocols ensure? What is TCP/IP? What does the TCP protocol actually do? What are the message data blocks called? What extra information is added to each data block? What does the IP protocol actually do? What does the IP add to each packet? Why are packet numbers important? Why might a message end up at its destination in the wrong order? Explain how packet switching works. What advantage does packet switching offer?

11. 12.

Network and host ID Every IP address contains two pieces of information: these are the network ID and the host ID.

V

Host ID

V

Network ID

V

V

32 bits

V

V

The network ID uniquely identifies the network, while the host ID uniquely identifies a hardware device that is on the network. In the following example, the first 24 bits (or first 3 octets) identify the network, and the last 8 bits (or last octet) identify the device.

V

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V

10.120.60

V

V

32 bits

V

V

The IP address 10.120.60.10 has a network ID of 10.120.60 and a host ID of 10 â&#x20AC;&#x201C; i.e. a packet sent to this address will be routed to device 10 on network 10.120.60.

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TECHNICAL ISSUES

Address classes To allow for different types of network, the 32 bit IP address can be arranged into five different formats, or address classes. The three most commonly used classifications are indicated below. TCP/IP classifications are used to define the number of possible networks and the number of different hosts. Class A 0 V

24 bits

V

V

Host ID V

Network ID 8 bits

Class A allows 126 unique network IDs and over 16,000,000 unique host IDs, so class A addresses are used for devices on the worldâ&#x20AC;&#x2122;s largest networks. The most significant bit, the one furthest to the left, must be set to zero, identifying the IP address as class A. The remaining bits can be set to one or zero, giving the unique network ID. Class B 10 V

Host ID 16 bits

V

14 bits

V

V

Network ID

Not many networks need so many host IDs, so class B uses 14 bits for the network ID and 16 bits for the host ID. Class B allows 16,384 unique network IDs and over 65,000 unique host IDs. The first two most significant bits, those furthest to the left, must be set to 1 and 0, identifying the IP address as class B. The remaining bits can be set to one or zero, giving the unique network ID.

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Class C 1 10 Network ID V

V

Host ID 8 bits

V

V

14 bits

Even 65,000 hosts is a large number for a single network, so class C can be used for smaller networks. Class C allows 2,000,000 unique network IDs and over 254 unique host IDs. The first three most significant bits, those furthest to the left, must be set to 1 and 1 and 0, identifying the IP address as class C. The remaining bits can be set to 1 or 0, giving the unique network ID. Summary Class

Number of networks

Hosts per network

Range of first octet

A

126

16,777,214

1 to 126

B

16,384

65,534

128 to 191

C

2,097,152

254

192 to 233

• Some IP addresses are reserved and cannot be used. Network address 127 is reserved to allow testing of network cards and protocol binding. Computers which are not linked to the Internet default to IP address 127.0.0.1 allowing testing of Internet commands such as WinSock. • Octets cannot be set to 255 – this value is used to set up network broadcasts. • Octets cannot be set to 0 – all packets that have an IP address that contain an all-zero octet are restricted to the local network and never passed to the Internet.

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Task 9 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

What information is held in IP protocol? What are hosts? Which two pieces of information are held in an IP address? What does the network ID identify? What does the host ID identify? How many bits are used to store an IP address? How many TCP/IP address classifications are there? How many networks does class A allow? How many hosts does class C support? Write down the leading octet structure for each of the three classifications. Write down the range of the class A first octet. Write down the range of the class B first octet. Write down the range of the class C octet. Classify the following IP addresses: (a) (b) (c) (d)

120.245.10.10 130.70.90.200 70.34.34.90 195.26.117.35

Network masks Every IP address has an associated network mask. The network mask is used to separate the network ID from the host ID. Each network class has its own network mask value. Network masks may only consist of the values 0 or 255. The 255 value masks out the network ID, leaving only the host ID.

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Class

Network Masks

A

255.0.0.0

B

255.255.0.0

C

255.255.255.0

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For instance, class A: IP address 102.165.80.20 Network mask 255.0.0.0 Host ID of 255.165.80.20 1 1 1 1 1 1 1 1 1 0 1 0 01 0 1 0 1 1 1 0 0 0 0 0 0 01 1 00 0

102.165.80.20 masked by 255.0.0.0 gives a host ID of 165.80.20

Task 10 Answer the following questions. 1. 2. 3.

What does a network mask do? List the network masks for each of the three classifications. Which two values can only be used in a network mask?

Sub-netting Suppose your school network has 400 hosts. This is too many for class C (254 max), but it would be wasteful to allocate class B addresses (which would allow 65,384 hosts). Also, there are only 16,384 class B networks allowed, which is not enough to give a unique class B address to each school. To get around this problem, sub-netting is used. Sub-netting uses network masks to split a network into a number of smaller networks. The class C network mask – 255.255.255.0 – allows a network to have only 254 host IDs. It requires that the first three octets be set at 255 – the remaining octet, which is normally set to zero, can in fact take a series of values. For example, 255.255.255.128 can be identified as a sub-net mask, as the last octet is non-zero. Sub-net values are defined as follows. (The sub-net must be a series of 1s followed by 0s.

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128 Binary Value

1 128

0 0

0 0

0 0

0 0

0 0

0 0

0 0

= 128

192 Binary Value

1 128

1 64

0 0

0 0

0 0

0 0

0 0

0 0

= 192

224 Binary Value

1 128

1 64

1 32

0 0

0 0

0 0

0 0

0 0

= 224

240 Binary Value

1 128

1 64

1 32

1 16

0 0

0 0

0 0

0 0

= 240

248 Binary Value

1 128

1 64

1 32

1 16

1 8

0 0

0 0

0 0

= 248

252 Binary Value

1 128

1 64

1 32

1 16

1 8

1 4

0 0

0 0

= 252

254 Binary Value

1 128

1 64

1 32

1 16

1 8

1 4

1 2

0 0

= 254

These are the only values that can be used in a sub-net mask. The following are legal sub-net masks: Class A

255.254.0.0

11111111 11111110 00000000 00000000

Class B

255.255.192.0

11111111 11111111 11000000 00000000

Class C

255.255.255.248

11111111 11111111 11111111 11111000

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How are sub-nets used to identify different networks? Sub-net mask 225.255.255.192

Host IP address 200.165.80.20

Host IP address 200.165.80.40

Class C IP address 200.165.80.20 Network mask 255.255.255.192 200.165.80.20 1 1 0 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 1 1 0 0 0 0 0 0 0 1 0 1 0 0

AND 255.255.255.192 V

Result

V

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 00 0 0 0 0 192

= 200.165.80.0

1 1 0 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 1 1 0 0 0 0 0 0 00 0 0 0 0

Class C IP address 200.165.80.40 Network mask 255.255.255.192 200.165.80.40 1 1 0 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 1 1 0 0 0 0 0 0 1 0 1 0 0 0

AND 255.255.255.192 V

V

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 00 0 0 0 0 192

Result = 200.165.80.0 1 1 0 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 1 1 0 0 0 0 0 0 00 0 0 0 0

The results are the same, as both hosts are on the same network.

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Sub-net mask 255.255.255.192

Host IP address 200.165.80.20

Host IP address 200.165.80.40

Class C IP address 200.165.80.20 Network mask 255.255.255.224 200.165.80.20 1 1 0 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 1 1 0 0 0 0 0 0 0 1 0 1 0 0

AND 255.255.255.240 V

V

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 0 0 0 0 240

Result = 200.165.80.16 1 1 0 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 1 1 0 0 0 0 0 0 01 0 0 0 0

Class C IP address 200.165.80.40 Network mask 255.255.255.240 200.165.80.40 1 1 0 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 1 1 0 0 0 0 0 0 1 0 1 0 0 0

AND 255.255.255.240 V

V

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 0 0 0 0 240

Result = 200.165.80.48 1 1 0 0 1 0 0 0 1 0 1 0 0 1 0 1 0 1 1 1 0 0 0 0 0 0 11 0 0 0 0

The results are different, so the hosts are on different networks.

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Gateway A gateway is a link between two different networks. Gateways make up part of a router. The router will have at least two network cards. Each network card has its own IP address, or gateway address. Each gateway address belongs to a different sub-net.

If sub-net mask results are different, then the packets need to be routed. The router passes packets from one network card to the other network card.

Task 11 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8.

What effect can sub-net masks have on a network? Write down the range of sub-net values. Copy the list of legal network masks. Explain how sub-net masks can detect that two IP addresses are on different networks. What are gateways? Which hardware device forms a gateway? How many network cards are needed to create a gateway? Explain what happens to a packet if the sub-net results are different.

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SECTION 4

The Internet is a seamless network that allows users to access information from all over the world. A number of regulatory non-profit making organisations have been set up to manage the development of the Internet and to standardise Internet controls. Some Internet regulatory boards/organisations include: • • • •

IANA/ICANN IETF Nominet W3C

IANA The International Assigned Numbers Authority was the authority responsible for administrating IP addresses and the management of DNS allocations of top-level domain names. There are two top-level domains: • country codes – ccTLD • generic – gTLD Country Codes .ac .ad .ae .af .ag .ai .al .am .an .ao .aq .ar .as .at .au .aw

Ascension Island. Andorra United Arab Emirates Afghanistan Antigua and Barbuda Anguilla Albania Armenia Netherlands Antilles Angola Antarctica Argentina American Samoa Austria Australia Aruba

.az .ba .bb .bd .be .bf .bg .bh .bi .bj .bm .bn .bo .br .bs .bt

Azerbaijan Bosnia and Herzegovina Barbados Bangladesh Belgium Burkina Faso Bulgaria Bahrain Burundi Benin Bermuda Brunei Darussalam Bolivia Brazil Bahamas Bhutan

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.bv .bw .by .bz .ca .cc .cd .cf .cg .ch .ci .ck .cl .cm .cn .co .cr .cu .cv .cx .cy .cz .de .dj .dk .dm .do .dz .ec .ee .eg .eh .er .es .et .fi .fj .fk .fm .fo .fr .ga .gd .ge

Bouvet Island Botswana Belarus Belize Canada Cocos (Keeling) Islands Congo, Democratic Republic Central African Republic Congo, Republic of Switzerland Cote d’Ivoire Cook Islands Chile Cameroon China Colombia Costa Rica Cuba Cap Verde Christmas Island Cyprus Czech Republic Germany Djibouti Denmark Dominica Dominican Republic Algeria Ecuador Estonia Egypt Western Sahara Eritrea Spain Ethiopia Finland Fiji Falkland Islands (Malvinas) Micronesia, Federal State of Faroe Islands France Gabon Grenada Georgia

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.gf .gg .gh .gi .gl .gm .gn .gp .gq .gr .gs .gt .gu .gw .gy .hk .hm .hn .hr .ht .hu .id .ie .il .im .in .io

French Guiana Guernsey Ghana Gibraltar Greenland Gambia Guinea Guadeloupe Equatorial Guinea Greece South Georgia Sandwich Is Guatemala Guam Guinea-Bissau Guyana Hong Kong Heard and McDonald Islands Honduras Croatia/Hrvatska Haiti Hungary Indonesia Ireland Israel Isle of Man India British Indian Ocean Territory .iq Iraq .ir Iran (Islamic Republic of) .is Iceland .it Italy .je Jersey .jm Jamaica .jo Jordan .jp Japan .ke Kenya .kg Kyrgyzstan .kh Cambodia .ki Kiribati .km Comoros .kn Saint Kitts and Nevis .kp Korea, DPR .kr Korea, Republic of

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.kw .ky .kz .la .lb .lc .li .lk .lr .ls .lt .lu .lv .ly .ma .mc .md .mg .mh .mk .ml .mm .mn .mo .mp .mq .mr .ms .mt .mu .mv .mw .mx .my .mz .na .nc .ne .nf .ng .ni .nl .no .np

Kuwait Cayman Islands Kazakhstan Lao PDR Lebanon Saint Lucia Liechtenstein Sri Lanka Liberia Lesotho Lithuania Luxembourg Latvia Libyan Arab Jamahiriya Morocco Monaco Moldova, Republic of Madagascar Marshall Islands Macedonia Mali Myanmar Mongolia Macau Northern Mariana Islands Martinique Mauritania Montserrat Malta Mauritius Maldives Malawi Mexico Malaysia Mozambique Namibia New Caledonia Niger Norfolk Island Nigeria Nicaragua Netherlands Norway Nepal

.nr .nu .nz .om .pa .pe .pf .pg .ph .pk .pl .pm .pn .pr .ps .pt .pw .py .qa .re .ro .ru .rw .sa .sb .sc .sd .se .sg .sh .si .sj .sk .sl .sm .sn .so .sr .st .sv .sy .sz .tc .td

Nauru Niue New Zealand Oman Panama Peru French Polynesia Papua New Guinea Philippines Pakistan Poland St. Pierre and Miquelon Pitcairn Island Puerto Rico Palestinian Territories Portugal Palau Paraguay Qatar Reunion Island Romania Russian Federation Rwanda Saudi Arabia Solomon Islands Seychelles Sudan Sweden Singapore St. Helena Slovenia Svalbard and Jan Mayen Is Slovak Republic Sierra Leone San Marino Senegal Somalia Suriname Sao Tome and Principe El Salvador Syrian Arab Republic Swaziland Turks and Caicos Islands Chad

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.tf .tg .th .tj .tk .tm .tn .to .tp .tr .tt .tv .tw .tz .ua .ug .uk .um

French Southern Territories Togo Thailand Tajikistan Tokelau Turkmenistan Tunisia Tonga East Timor Turkey Trinidad and Tobago Tuvalu Taiwan Tanzania Ukraine Uganda United Kingdom US Minor Outlying Islands

.us .uy .uz .va .vc .ve .vg .vi .vn .vu .wf .ws .ye .yt .yu .za .zm .zw

United States Uruguay Uzbekistan Holy See (City Vatican State) Saint Vincent & Grenadines Venezuela Virgin Islands (British) Virgin Islands (USA) Vietnam Vanuatu Wallis and Futuna Islands Western Samoa Yemen Mayotte Yugoslavia South Africa Zambia Zimbabwe

Generic Codes .com

Commercial

.edu

Academic

.gov

Government

.int

International organisations

.mil

Military

.net

Internet network

.org

Non-commercial

Check out the following web address: http://www.iana.org/gtld/gtld.htm

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The authority assigns ‘well known’ Internet port numbers. Some of these port numbers are shown below. Service FTP

Port number 21/22

Telenet

23

HTTP

80

NNTP

119

SSL

443

Gopher SNMP

70 161

Kerberos

88

TFTP

69

DNS

53

Check out the following web address: http://www.iana.org/numbers.html

ICANN Since 1999, the administration functions of IANA have largely been taken over by a new organisation – ICANN (International Corporation for Assigned Names and Numbers). The US government set up ICANN to oversee and administer developments in: • • • •

Internet protocol Internet domain name system generic top-level domain names country code domain names.

Check out the following web address: http://www.icann.org/

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REGULATING THE INTERNET

Nominet Nominet.uk was set up in 1996 as a private non-profit making company to control the use of the top-level .uk domain A voluntary group called ‘The Naming Committee’ managed .uk in the 1980s. In the 1990s domain names were being sold by commercial organisations and there was a clear need for control. As a result, Nominet was formed as an authorising body to control second-level domain names in the UK. Second-level domain names managed by Nominet .co.uk

Commercial organisations

.me.uk

Personal

.org.uk

Non-commercial

.ltd

Registered company name

.plc

Registered company name

.net.uk

Internet service providers

.sch.uk

Schools

Second -level domain names not managed by Nominet .ac.uk

Academic

.gov.uk

Government

.nhs.uk

National Health Service

.police.uk

Police

.mod.uk

Ministry of Defence

Nominet registration deals with: • • • • •

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registration of domain names accuracy of domain name registration transfer of domain name registrations cancellation of domain names disputes.

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REGULATING THE INTERNET

W3C The World Wide Web Consortium (W3C) leads developments on the World Wide Web. Based at the Massachusetts Institute of Technology (MIT), the W3C is an open forum, which anyone can apply to join, and which deals with technical developments. W3C has led the change in the WWW from a hypertext network to a fully multimedia network. W3C has made recommendations on the development of: • • • • • • • • •

HTML 4 XHTML XHTML Basic cascading style sheets XForms PNG – portable network graphics format SVG – scalable vector graphics XML – encryption web access guidelines.

Check out the following web address: http://www.w3.org

IETF The Internet Engineering Task Force has a similar role to the W3C. It consists of many sub-groups carrying out research into all aspects of Internet development. Again, it is open to any interested person to join. Check out: http://www.ietf.org

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Task 12 Answer all of the following questions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

54

State the two types of top-level domain. What are contained in country top-level codes? List the seven top-level generic domains. List the four main regulatory Internet bodies. What does IETF regulate? What does IANA regulate? Which port number is used to receive HTTP? Which port number is used by DNS servers? Which port numbers are used by FTP? Which organisation regulates .uk? What does Nominet control? List the second-level domain names that Nominet does not control. What is the main difference between .org.uk and .co.uk? What does W3C regulate?

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INTERNET SECURITY

SECTION 5

There are four main threats to a computer system and/or network from the Internet: • • • •

viruses unauthorised access (hacking) denial of service information theft.

Viruses Viruses are background computer applications that can copy themselves from one computer system to another. Viruses need not cause any harm to a computer system; but they may cause untold harm. Any computer system or network that is linked to the Internet must have virus protection. But remember, any virus protection is only as good as the last update. If your virus protection software is out of date, then it is totally useless. Viruses are being continually produced and sent out over the Internet. The summer of 2003 alone saw MSBlaster, Backdoor.Jittar, VBS Mill H, Trojan.Mumuboy, Trojan.Vardo and many more besides.

Unauthorised computer access The intent to gain unauthorised access to a computer system (sometimes called hacking) is an offence under the Computer Misuse Act. Hackers may not do any real harm – some just like the challenge of accessing a secure network, often leaving a message explaining that the network has been hacked. Hacking a network is generally quite difficult, needing a lot of networking knowledge. Generally speaking, if a network is hacked it is most likely that someone’s password was guessed or acquired. Regular changing of passwords is therefore a simple way of stopping unauthorised access.

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Denial of service Denial-of-service attacks are Internet attacks on a particular IP address. In recent years Microsoft, The White House and The Pentagon have all been targeted. The IP address is swamped by numerous messages, stopping the website from sending or receiving legitimate information. The simplest denial-of-service attack requires many Internet users to Ping a particular IP address. The IP host then becomes swamped with Ping replies. Firewalls and packet filtering can be used to prevent denial of service attacks.

Information theft Viruses, unauthorised access and denial of services all leave tell-tale signs. With information theft, there is no way of knowing if someone has copied your files or your credit card number. Information thieves do not leave messages thanking you for your bank details! It is worth remembering that 80% of all Internet attacks come from authorised users. It is much easier for an authorised user to make an attack on a computer network than for an unknown Internet user. The UK Computer Misuse Act makes it a criminal offence to send viruses, gain unauthorised access to a computer system, deny computer access, or to copy files without permission.

Protection Computer systems and networks that are linked to the Internet require protection from Internet attacks. This can be achieved by using: • packet filtering routers • firewalls • proxy servers. Each of these three methods restricts access to the Internet. The host is connected to either a packet filtering router, or a firewall, or a proxy server. The host is not directly connected to the Internet. Each of these three methods hide the host ID from the Internet. The only IP

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address passed out to the Internet is the gateway address, giving security and privacy for the host.

Packet Filter Router Gateway address 192.10120.10

or Firewall

Internet

or Proxy Server Host ID126.10.0.10

Packet filtering routers Routers are switches that have access to routing tables. Routing tables are dynamic databases that contain data about destination IP addresses, and how many jumps it takes to reach a particular destination. Routers direct data packets from source IP address to destination IP address. Packet filtering routers can filter out ‘unwanted’ IP addresses. This is achieved by writing a set of rules, which accept or prohibit an IP address. These rules are maintained by the network manager. Example packet filtering rules Rule Action Local Local Number Host Port 1 Block 2 Allow 141.34.16.24 80

3

Allow

25

4

Allow

>1023

5

Block

External External Host Port 123.10.10.4.2

Comment Block all Allow all Internet access Allow email replies Allow all Internet replies Block everything else

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Once all of the rules have been assembled, only the allowed packets will be permitted. Packet filtering cannot check the contents of a packet – only the attached IP addresses. Firewall A firewall is a single secure network connection to the Internet, which controls the flow of traffic between the Internet and the client. Like packet filter routers, firewalls require a set of rules. The usual firewall default setting is to block everything. The firewall needs to be configured to allow packets through. Firewalls are fail-safe, i.e. if an attack or breach in security is detected, the firewall will close down the service or cut off all Internet access. Unlike packet filter routers, which can only allow or block IP addresses, a firewall can read the content of the packets, as well as save information. Stateful inspection allows the firewall to check the contents of the packet before the packet is allowed through the firewall. Proxy server A proxy server is a web server that acts on a user’s behalf. Proxy servers are used to link LANs or Intranets to the Internet using only one source IP address – this is called IP aggregation. Intranet users are linked to a proxy server, not to the Internet. Only the proxy server is linked physically to the Internet. Users request web pages from the proxy server; the proxy server then changes the source IP address to the proxy server IP address. Once the required web page is returned from the destination, the proxy server changes the source destination back to the client source IP address. A proxy server can also be used to cache web pages; and can be used as part of a firewall.

Internet

Proxy server

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Task 13 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

List the four Internet security threats. Define a computer virus. What is meant by unauthorised access? What is meant by ‘denial of service’? Which of the four security threats is the hardest to identify? List the three ways in which computer systems can be protected from security threats. What is a router? What are routing tables? How are routing tables updated? How does filtering work? What are packet filter rules and what do they do? What is a firewall? What is the main difference between packet filtering routers and firewalls? What is the default setting for all firewalls? What happens if a firewall detects a breach in security?

Encryption Encryption is a method of sending secure information by masking, or disguising, each character with an arbitrary number. If we want to encrypt the message ‘HAVE A NICE DAY’ we would need to: 1. 2. 3. 4.

change the message into the ASCII equivalent decide upon an arbitrary random number to mask out the characters in the message mask off each ASCII code apply a formula, using the ASCII number and the masking number.

In this example, taking 255 as the masking number: Plain Text

H

A

V

E

ASCII

72

65

86

69

Mask

A 32

65

32

N

I

C

E

78

73

67

69

32

D

A

Y

68

65

89

255 255 255 255 255 255 255 255 255 255 255 255 255 255 255

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Add the two numbers together to create the encryption code: Plain Text

H

A

V

E

ASCII

72

65

86

69

A 32

65

32

N

I

C

E

78

73

67

69

32

D

A

Y

68

65

89

Mask

255 255 255 255 255 255 255 255 255 255 255 255 255 255 255

Encrypt

327 320 341 324 287 320 287 333 328 322 324 287 323 320 344

The message can now be transmitted in its encrypted form: 327320341324287320287333328322324287323320344 All the receiver has to do is subtract the masking number of 255 from each group of three digits in order to decrypt the message. In reality, the masking number is not added to the ASCII code. ‘Exclusive Or’ (XOR) is used to create the encryption. XOR (gives an output if one or other of the binary digits is set but not both binary digits being set) allows a value to be masked and unmasked using the same operation. In fact, computer-generated graphics use XOR to place a graphic on a background and then remove it from the background, keeping the background complete without the need to refresh the screen. The masking number is usually known as the key. The sender uses XOR to encrypt every character:

Character Mask Encrypt

A 255 XOR

0 1 1

1 1 0

0 1 1

Binary 0 0 1 1 1 1

0 1 1

0 1 1

Decimal 65 255 190

1 1 0

The letter ‘A’ is now sent as 10111110, which is the ASCII code for a comma. The receiver deciphers the message by XORing the encryption versus the key: Encrypt Mask/Key Character

255 A

1 1 0

0 1 1

1 1 0

1 1 0

1 1 0

1 1 0

1 1 0

0 1 1

This is an example of a symmetric encryption system, as the same mask/key is used to encrypt and decrypt the message.

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Key distribution problem Encryptions, like all code systems, require that the sender and receiver know the key to unlocking the code. If the receiver does not know the key, then he/she cannot read the message – it is as simple as that. Can a sender distribute a key so that only the receiver can use it in order to decipher a secret message? When you are sending your credit card details on the Internet, you want to make sure that these details are secure. You want the receiver and only the receiver to be able to read your details, but you need to send the keys openly over the Internet. The key distribution problem can be resolved by using a special piece of mathematics, called a one-way mathematical function. Question: I am thinking of a number that, when I double it, I get a value of 24. What is the number? Answer: The number is 12. All mathematical functions have inverses and are called two-way functions: • the opposite of doubling is halving • the opposite of add is subtract • the opposite of multiply is divide. Question: I am thinking of a number that, when I divide it by 10, I get a remainder of 1. What is the number? Answer: The number is obviously 11. If you divide 11 by 10, the remainder is 1. But is 11 the only answer? What about 21, or 31 or 41 or 51 or 1,000,001? Calculating remainder (or modulo) value gives a family of possible answers. This is an asymmetric (or one-way) function. All Internet security is based upon modulo arithmetic. Public keys Public keys are freely distributed throughout the world. A message, or credit card details, encrypted using public keys can be sent out on the

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Internet with the knowledge that the information cannot be read by a third party. But why is the message secure from prying eyes? Question: I am thinking of a number, and when I divide the number by 7156177199311371, the remainder is 9117667347513. What is the number? Answer: You need a super-computer! In this case, the public key is 7156177199311371 and the transmitted value is 9117667347513. So, to break the code, all you need do is find the number that, when divided by 7156177199311371, gives you a remainder of 9117667347513. Easy? RSA encryption RSA is named after its three American inventors: Rivest, Shamir and Adleman. It requires the use of three formulae, which exploit the asymmetry of modulo arithmetic. If you are into mathematics, you might want to try these equations. This Unit only requires that you gain an understanding of what is required to encode and decode an Internet message. Code = Asciie mod Pk Dk × e = N mod((p–1)(q–1) Ascii = Code Dk mod(Pk) Where: • • • • • •

Code is the encrypted value that will be sent on the Internet Ascii is the ASCII code of each character in the message Pk is the public key Dk is the decode key N is an arbitrary number needed to calculate Dk and e p and q are the private keys.

Private keys have only two rules: 1. 2.

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they must be prime numbers they must be different prime numbers.

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Generally, these two prime numbers are always referred to as p and q. Let’s say that: p=7 and q=11 My public key is the product of these two private keys: p × q = 7 × 11 = 77 Pk = 77 The decode key is an exponent, which must be large enough to generate a set of unique remainders when divided by the public key. Dk × e = 1 mod((p–1)(q–1) 5 × Dk = 1 mod((7–1)(11–1)) as e =5 = 1 mod(6×10) = 1 mod(60) Dk = 11 and e = 5 So I am now ready to receive secure messages; I tell the whole world that Pk = 77 and e = 5 and sit back and wait for my first message. If you want to send me a short message, like the letter ‘A’ all you need to do is combine my two public keys and the ASCII code for A, which is 65. Calculate the encryption code: Code = Asciie mod Pk Code = 655 mod 77 = 1160290625mod 77 = 32 I receive the encrypted message 32. I can decode the message using the last of the three formulae. Ascii = CodeDk mod(Pk) = 3211mod(77) = [ 32 5 mod(77) × 326 mod(77)] mod(77) = [ 65 × 1 ] mod(77) = 65 You sent me the ASCII code 65, which is the letter ‘A’.

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RSA is an asymmetric encryption, as it uses two different keys – one to encode and a different key to decode. Even this simple example produced one or two large numbers and looks very secure and unbreakable, but like the Lorenz code machine, RSA does have an Achilles heel – and it is the public key. If the public key can be factorised, then both p and q will be known and the decode key can be calculated. To ensure better security, both p and q should be prime numbers greater than 549755813888 – that is 40-bit security. Public keys will have 80 bits and should be more difficult, but not impossible, to factorise. In America, public keys use strong primes, i.e. prime numbers with more than 128 bits, yet Internet Explorer 5.5 and Outlook Express only offer at best 56-bit security, while Internet Explorer 6.0 offers 128-bit security. Do not worry! You will not need to do any of these calculations! It is only important that you understand that RSA is quite complicated and requires a lot of calculations. Encryption strength Internet Explorer will tell you its encryption strength by selecting About Internet Explorer from the Help menu.

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Browser encryption functions There are a number of browser encryption functions, including: • • • • • • •

DES IDEA Blowfish Shark AES RC2 GOST.

IDEA (International Data Encryption Algorithm) IDEA is a block cipher, which uses a 128-bit cipher key to encrypt blocks of plain text. The algorithm is very complicated, using sub-keys to carry out a series of modulo arithmetic calculations. The encryption process requires the use of 52 sub-keys! First it generates the 52 sub-keys from the original 128-bit cipher key. The plain text is then split into 64-bit blocks. Each block of text is now ciphered using modulo arithmetic and one of the sub-keys. Text Text Text Text

block1 block2 block3 block4

× + + ×

sub-key1 sub-key2 sub-key3 sub-key4

→ → → →

code1 code2 code 3 code4

Notice that IDEA uses both add and multiply. Each of the codes is combined to produce a new secure cipher. Code1 XOR Code3 → Secure code1 Code2 XOR Code4 → Secure code2 IDEA then performs this process a further seven times, that is each block of the plain text is encoded eight times. DES (Data Encryption Standard) DES is also a 128-bit block cipher. It encrypts and decrypts 64-bit data blocks. Each 64-bit data block passes through 16 different permutations, so that means the data in each data block is combined together 16 times.

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Blowfish Blowfish is a free alternative, replacing DES and IDEA. Blowfish has a variable cipher key length, from 32-bit to 448-bit, and requires 14 runs to encode each block of plain text. PGP (Pretty Good Privacy) Although RSA is secure, it requires a lot of calculations. Each character in the message needs to be encrypted before sending and decrypted on arrival. There was a need for a fast and secure system. RSA was secure but not fast enough. In the late 1980s, Phil Zimmermann developed PGP, which is a combination of RSA asymmetric and symmetric encryption. Zimmermann’s idea was to use RSA to code a symmetric key and then send the encrypted message. The receiver need only do one RSA calculation in order to find the key. The message can then be quickly decoded. PGP = RSA encrypted key + encrypted message Message = ‘HAVE A NICE DAY’ Key = 255 Encrypted message = 327320341324287320287333328322324287323320344 RSA encrypts 255 to give a new code of 61. PGP message = 61 + 327320341324287320287333328322324287323320344 On receiving the PGP message, the RSA encrypted code of 61 can be decoded and the message quickly unmasked. Phil Zimmermann’s development of PGP unfortunately brought him into conflict with his own government. He was charged with selling munitions to foreign countries. Strangely enough, PGP software was classified as munitions as it could help a foreign power in time of war. Zimmermann was the subject of many US Grand Jury investigations. In 1996, the US Attorney General dropped all cases against him. PGP’s importance was realised when the Iron Curtain finally came down. Zimmermann received many e-mails from Soviet dissidents, thanking him for PGP, as they had used it to pass secure messages.

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Summary • Encryption is a method of masking data so that a third party cannot intercept the data. • Encryption uses cipher keys to scramble the data. • The key distribution problem outlines the problems of sending the cipher key between sender and recipient. • RSA uses public and private cipher keys. • A public key is freely available to everyone on the Internet and is used to encrypt the message. • A private key is secure and is used to decipher the message. • Both public and private keys are derived from large prime numbers. • RSA requires many complex calculations to encode and then decode a message. • RSA requires that the message is encrypted and decrypted, character by character. • PGP uses RSA to encode the cipher key. • PGP does not require numerous complex calculations. • RSA is slow compared to PGP. • PGP is more suited to Internet traffic. Check out the following websites to get more information on PGP and RSA: http://www.pgpi.com http://www.rsa.com

Task 14 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

What is encryption? Explain how encryption works. Why is it important that both the sender and the receiver know the key? What is meant by the key distribution problem? What is meant by a one-way mathematical function? What are public keys? What are private keys? How many different mathematical formulae are needed for RSA security? Why is the publishing of private keys not a security risk? What is RSA’s Achilles heel? Why was PGP developed? Why is PGP quicker than RSA?

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Secure sockets The secure socket layer (SSL) is a protocol that is used to create an encrypted link between two computer systems. The secure socket layer prevents communications from being intercepted by a third party. Source

Destination

Receive – Port Number 80

Receive – Port Number 80

V

Send – Port Number 2100

V

Send – Port Number 2100

HTTP requires that all TCP/IP packets be received on Port number 80. A TCP/IP packet is sent through any random port number. The sender generates a random number, which is then used to identify the port number. The combination of send and receive ports creates a socket. The SSL provides integrity, because the Internet user’s browser must ensure that the remote server is identified. Passing a server validation certificate ensures that the web server is secure. Privacy is ensured, because a third party cannot compromise the information, as the SSL data is encrypted.

Site tracking Site-tracking software collects and analyses the data that is generated by Internet traffic. The simplest type is a hit counter, which can be incorporated into a web page. A hit counter stores data about the number of visitors who have browsed the website. Site-tracking software depends upon the sending and receiving of cookies. Most web servers generate log files, which record information about the Internet user’s browser software, their ISP, the time and date a website was visited, and which web pages were accessed.

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Some hosting companies (e.g. Lycos) allow other types of site tracking, with a breakdown on the types of browser that were used to visit the site, as well as analysis on which web pages were most often visited and downloaded. There are many other site-tracking tools.

Privacy issues Remember that when you are using the Internet, any site-tracking software will have logged your IP address, the name of your ISP, the type of web browser that you are using and the time and date. Site tracking will also record the web pages that you have visited and the information that you have downloaded. Many Internet users think that they are anonymous, but site tracking logs most Internet details. Check out the following website: www.evcforum.net

Task 15 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8.

What does a secure socket create? What does a secure socket prevent? What is a socket? Explain how a socket is created. What does site-tracking software do? What is the simplest type of site-tracking software? List the information that is logged by site-tracking software. Why might it be important to know which web pages are visited the most?

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SECTION 6

Legal implications Currently there are two UK laws that are relevant to the Internet and which are intended to protect the individual. These are: • The Data Protection Act 1998 • The Computer Misuse Act 1990.

The Data Protection Act Most people in Britain are aware of the Data Protection Act (DPA). It has been updated regularly since coming into force, and itself replaced an earlier version. This Act gives us a ‘right to privacy’, which means that sensitive information about us is kept confidential. The Data Protection Act states that if any person, organisation, company or business (data user) wishes to hold or process personal information about an individual (data subject) on a automatic retrieval system (database) then they must be registered with the Data Protection Registrar’s office. Principles The Act has eight basic principles. 1. 2. 3. 4. 5. 6. 7. 8.

Information may only be obtained and processed fairly and lawfully. Information may only be held for specific purposes. The information is not to be used for any purpose other than that for which it was intended. The information is relevant and adequate for the purpose. The information is accurate and up to date. The information is not kept longer than necessary. The information should be made available to the individual concerned and the individual can have corrections made. Information is kept secure.

Exemptions 1. No right to see information that is needed for national security. 2. No need to register if information is being gathered for recreation.

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3. 4.

Non-profit making member organisations, such as clubs and churches, do not need to register if all members agree. Mainly governing things like tax affairs.

Personal data on web servers The Internet is a large database, which contains a lot of information; some of this is personal/ sensitive information. Under the law, Internet users must be registered if they process personal information. Does this include information that is freely available on the Internet? If a website uses submission forms or visitors’ books to gather personal data, it is unlikely that the site is within the letter of the law, unless registered under the DPA. The gathered data will be held on a web server. The organisation that controls the server will need to register under the DPA, but organisations outside the UK have no obligation to register under the Act, even though they hold personal data about UK citizens. The situation becomes more confused when considering who is actually gathering the data. A UK citizen, who is gathering personal data by means of submission forms or visitors’ books for recreational fun is exempt, and does not need to register. A UK business that gathers personal data by the same means will need to register. The business may not intend to process the information gathered, but it will still need to register. Once registered, the business will need to notify all data subjects that data is being held about them, along with a description justifying the need for collecting the data and explaining the purpose for which it will be used. A non-UK business does not need to register and can use the Internet to gather personal data, perhaps selling the information on to a third party. There is no binding international agreement on the storing and processing of personal information. Strangely enough, educational institutions – universities in particular – that have placed employees’ personal data on the Internet are complying with the Data Protection Act, provided that the institution

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has already registered under the Act, stating that they are storing employee data. Check out the following website and look up departmental details: www.strath.ac.uk Search engines Search engines give Internet users the ability to carry out name searches. Most Internet users have searched for information about themselves or searched for information about famous people. The Internet user then becomes a data user, as they are processing personal information, and under UK law should register under the DPA! Perhaps the exemption that allows individuals to store and process information for recreation may apply, but this was written into an earlier version of the Act, long before the Internet was in common personal use. • Have you ever downloaded information about yourself from the Internet? You were a data user and you should have registered under the DPA! • Have you ever searched for any of your friends or relatives on the Internet? You are again a data user and should have registered as such.

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Task 16 Answer the following questions. 1. Define a data user. 2. Define a data subject. 3. List the four main exemptions to the terms of the DPA. 4. Outline the problems with gathering personal data using a visitorsâ&#x20AC;&#x2122; book. 5. If an individual uses the Internet to gather personal data, will he/she need to register with the Data Protection Registrar? Explain your answer. 6. If a UK business uses the Internet to gather personal data, will it need to register with the Data Protection Registrar? Explain your answer. 7. Explain how a search engine could be used to gain personal information. 8. Outline the problems of storing personal information on a web server. 9. Explain why using a search engine to look up your own name may be considered illegal under the DPA. 10. Explain why downloading information about Madonna could be seen as infringing the DPA. 11. It is possible to view open-access web pages, often found in American academic websites like the University of Texas. These pages contain personal information, such as name, date of birth, address, etc. Explain why this data provision is not legal in the UK. 12. Why are international agreements needed to protect our personal information?

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The Computer Misuse Act This Act tries to close the loopholes in civil law, as well as create legislation regarding the possible misuse of computer systems. There are four basic infringements: • • • •

hacking sending viruses service denial copying of files.

Hacking Hacking is the use of a computer to gain illegal access to another computer system. Often, a hacker just does it for kicks, just to see if they can break in, but this is illegal. Others hack into computer systems to make illicit gains or to cause damage; obviously this too is illegal. Viruses The Act also covers the distribution of computer viruses. It is an offence to cause damage to a computer system, or to cause deliberate loss of files by sending a computer virus. • • • • •

Computer viruses spread from one computer to another. Viruses can cause harm to your computer system. You may lose everything on your computer. Your computer may stop working. The virus might be sending information about you to other people.

How do you get viruses? If you are connected to the Internet, you may get a virus. Viruses are often sent as e-mail attachments that you are instructed to download. You might get a copy of a game from one of your pals, which unknowingly has a virus attached to the game. This can happen with any type of file sharing. How do I protect myself? The best way is to have virus protection software running in your computer system. This software is only as good as the information that it contains. If the software is a month or two out of date, then it is useless.

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Court cases Example 1 In September 2003, an 18-year-old British schoolboy hacked into the American Nuclear Weapons Laboratory by cracking the security software with a program that he had written. The intrusion triggered a full-scale alert at the Fermi Research Labs in Chicago. As a result, the lab’s computer systems were shut down for three days. The subsequent cost of restarting the computer system was £22,000. It was said that he was only breaking into the computer system in order to use its power to allow him to download music and videos from the Internet. He passed on passwords to friends and other hackers. The policemen who arrested him said that he was ‘very good and admitted everything’. The boy appeared at Bow Street Magistrates Court and was given unconditional bail, so that he could continue with his studies. Example 2 A teenager charged with computer hacking offences appeared before magistrates in west Wales. He faced 10 charges under the Computer Misuse Act of downloading unauthorised information. He was also charged on two counts of deception by obtaining computer equipment worth £1,399 and obtaining other items with a value of £400. He was given unconditional bail. Example 3 A 26-year-old man (‘the Black Baron’) faced 11 charges in respect of two virus programs. He was described in court as a typical ‘anorak’, being lonely and friendless. His solicitor said that he had ‘a particular talent’ and had ‘written something extraordinary’, and if directed properly, he could have ‘made a place for himself’. The police claimed that he had ‘caused mindless havoc’ all over the world. He received a sentence of 18 months’ imprisonment. Service denial Service denial can be the deliberate act of destruction of computer systems and wiping of files, stopping users from gaining access. This is often referred to as computer vandalism.

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It can also take the form of a service denial attack, where a web server receives countless user requests. Eventually, the server crashes, denying access to legitimate users. Copying of files Files and credit card numbers are copied from the user’s computer system. What makes this infringement worse than the other three is that the hacker does not leave any evidence that they have been there. They just copy the information and go.

Task 17 Answer the following questions. 1. 2. 4. 5. 7. 8. 9. 10.

List the four misuse infringements. What is a hacker? How might you get a virus? How do you protect your computer from viruses? What is service denial? Which is the worst of all computer infringements? What does the Computer Misuse Act attempt to do? Is there a need for international policing of the Internet?

International policing The Internet is worldwide, crossing countries with different cultures – so it is difficult to see how international policing would work. In February 1997, the European Conference on Combating Violence and Pornography on the Internet was convened in London. The conference looked at the technical and moral issues surrounding policing the Internet. All proposals would be put to the European Union to influence European policy. Delegates attended from all over Europe. There were many contrary views expressed. Delegates could not agree on a definition of offensive materials, or even on a need to control the distribution of offensive materials. British Telecom representatives looked at the problem from an industry perspective. If BT comes across any illegal material, they report the contents to the Internet Watch Foundation.

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By December 1996, the Internet Watch Foundation (a UK-only organisation) had received only 28 reports from Internet users, which led to five images being removed from UK servers. Engineering and technical representatives outlined some technical solutions, including address filtering, service filtering and content labelling/filtering, which could be used to monitor illegal content on the Internet. The German Committee of Enquiry into Media and Violence stated that they were against the policing of the Internet for pornography, when it is widely available on German streets. The Committee had difficulty in defining the word ‘pornography’, stating that a definition would be complicated in an international environment such as the Internet. The Netherlands representative stated that censorship does not work and that we should not allow governments to tell us what to do about our sex lives. They also stated that production of pornography, rather than possession of it, should be illegal, as in the Netherlands. The French Ministry for Telecommunications and Postal Affairs stated that the French would only work with the Organisation for Economic Co-operation and Development, and had no interest in the ECCVP.

Task 18 Write a short essay outlining the problems of internationally policing the Internet.

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SECTION 7

HyperText Markup Language Although hypertext systems have been in use for many years, it was the development of HTML by Timothy Berners-Lee that allowed everyone to put information onto the web. Prior to this, information could only be placed on a network using complicated code. HTML is a scripted language that is easy to understand and easy to use. Browser viewing When you view or, more correctly, browse a website you can interact with it and read the information. As a browser, you cannot change the information that is being displayed. You use a piece of software called a web browser, like MS Internet Explorer. Author viewing When you interact with a website as an author, you can change the website. (You are only allowed to change your own website; you will not be able to change other people’s websites.) To author a website you need authoring software. There are a number of software packages, that you can use: • • • •

MS FrontPage Dreamweaver MS Word MS PowerPoint.

FrontPage and Dreamweaver are specialised web-authoring packages, while Word and PowerPoint are general purpose document-creation packages with authoring tools.

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Client-side and server-side HTML scripts are hosted (stored) on a web server as a document. The user (client) downloads the HTML document to their computer system. The browser software then reads the script and displays the document as intended. Server side

Client side

Task 19 Answer all of the following questions. 1.

Explain the difference between (a) browsing a web page (b) authoring a web page.

2. 3. 4.

Where are web page HTML scripts stored? Where are HTML documents displayed? Explain the difference between server-side and client-side.

HTML documents All HTML documents have the same structure and use tags to encode the actual content. A tag is a word or phrase that a browser recognises as a command. HTML tags are written in angled brackets, thus: <tagtext>. Many commands require an opening and closing tag, e.g. <body> </body>. Equally, many tags have attributes, which add to, or put conditions on, the command in the tag, e.g. <body bgcolor=nnnn>.

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The structure of an HTML document: <html> <head> This section does not display </head> <body> This is the section of the document that is displayed. All of a web page content is contained in this area. </body> </html>

Each HTML document must start with a new document tag <html>. The next tag is the header <head>. Header text is not displayed in the HTML document, but is used to set up special instructions and allocate keywords. Headers must have a closing tag. The next part of the document is <body>; this is the section of the document that is displayed in the web page. Notice that <html> and </html> tags surround the document, while the remaining tags are nested inside. Remember that a <> tag will switch on an HTML command, while the </> tag will switch the command off.

Task 20 Answer the following questions. 1. 2. 3. 4. 5.

What are tags? What is the starting tag of every HTML document? Which part of an HTML document is not displayed? What is contained between the <body></body> tags? What is the last tag of every HTML document?

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Tags and structure Have a look at the following HTML document text:

<html> <head> <title>”HOME PAGE”</title> </head> <body> This is my Home Page<br> <br> I am interested in computers.<br> </body> </html>

The <head> tag contains <title> information. When the web page is being displayed in a browser, the title is displayed in the task bar. All HTML documents should contain a title. Another tag is included in the body. The <br> tag is used to break the lines of text – to take a new line. (HTML does not recognise RETURN or space bar commands.)

Task 21 1. Use Notepad/Simple Text, or any other text editor to enter the ‘Home Page’ HTML script shown above. 2. Save the document with either an .htm or .html extension, with the name ‘test’. Set the Save as type as All files. (If this is not done, then the file will be saved as a text file (.txt) and will not display in a browser.) 3. Now display ‘test.html’ in your browser.

You have created your first simple web page. As you can see, it is quite easy to do. There is no complicated computer code, no complicated structure; just text and HTML tags.

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Task 22 Answer the following questions. 1. 2. 3. 4.

Where are web page titles displayed? Which keyboard signals are ignored by HTML? What does the <br> tag do? Which file extension must be used when saving a web page?

Using paragraphs An alternative to the <br> tag is <p>, which, with </p>, can be used to enclose paragraphs. This also inserts a line space between paragraphs. Try the following:

<html> <head> <title>”Home Page”</title> </head> <body> <p>I am a student at…, studying the Internet Unit for Higher Information Systems, and having a whale of a time learning how to create web pages using HTML.</p> <P>This example is to show how to split up extended text into paragraphs, with a line space between them.</p> </body> </html>

What is transmitted on the WWW? The simple answer is just simple text! The web server sends out HTML script, which is a text document. Clearly, the amount of script contained in a document affects the transmission speeds over the Internet. The larger the script, the longer it will take to be transmitted from server to client.

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Task 23 Create a simple web page. 1.

Use a text editor, such as Notepad, to enter the following HTML script: <html> <body> My Home Page <br> </body> </html>

2. 3.

Save as ‘Home Page1.html’. Take care to ensure that the file type is set to All. Double click on ‘Home Page1.html’ to display the document in your browser.

Click on the View menu option and select Source.

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INTRODUCING HTML

You will see the HTML script that you have just entered.

Task 24 1. Now use Microsoft Word, or any other web authoring software, to create the same web page. 2. Save as ‘Home Page2.html’. 3. Double click on ‘Home Page2.html’ to display the document in your browser. It should look identical to ‘Home Page1.html’. 4. Click on the View menu option and select Source.

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You will see something like this: <html xmlns:o=”urn:schemas-microsoft-com:office:office” xmlns:w=”urn:schemas-microsoft-com:office:word” xmlns=”http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv=Content-Type content=”text/html; charset=windows-1252"> <meta name=ProgId content=Word.Document> <meta name=Generator content=”Microsoft Word 9"> <link rel=File-List href=”./MY%20HOME%20PAGE_files/filelist.xml”> <title>MY HOME PAGE</title> <!—[if gte mso 9]><xml> <o:DocumentProperties> <o:Revision>1</o:Revision> <o:TotalTime>1</o:TotalTime> <o:Pages>1</o:Pages> <o:Lines>1</o:Lines> <o:Paragraphs>1</o:Paragraphs> <o:Version>9.3821</o:Version> </o:DocumentProperties> </xml><![endif]—> <style> <!— /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:””; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:”Times New Roman”; mso-fareast-font-family:”Times New Roman”;} @page Section1 {size:595.3pt 841.9pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;}—> </style> </head> <body lang=EN-GB style=’tab-interval:36.0pt’> <div class=Section1> <p class=MsoNormal>MY HOME PAGE</p> <p class=MsoNormal><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></ o:p></p> </div> </body> </html>

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You certainly didn’t enter all of this script! So where did this come from? Microsoft Word, like other icon-based web authoring packages, generates extra script. For example, the script shown below sets up a link to an extra directory called MY HOME PAGE2_files. This directory/ folder contains all the graphics that will be displayed in the web page. <link rel=File-List href=“./MY%20HOME%20PAGE_files/filelist.xml”> Download efficiency This extra script needs to be transmitted over the Internet and downloaded into the browser. The Internet user wants the web page to be downloaded and displayed in the shortest period of time possible. This extra code affects the download efficiency of the web page. Compared with using a web authoring package, HTML hand scripting is not as user friendly, but the transmission overheads are drastically reduced, increasing the download efficiency. Other factors that affect download efficiency are the number and the size of the graphics files, animation files and sound clips that are to be displayed on a web page. These types of file can require a lot of storage space and hence can take a long time to download. The use of file compression can reduce this problem. It is important to remember that Internet users expect fast operation.

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Task 25 Answer the following questions. 1.

Which of the two scripts will be transmitted more quickly over the Internet?

Home Page1.html

<html> <body> My Home Page </body> </html>

Home Page2.html

<html xmlns:o=”urn:schemasmicrosoft-com:office:office” xmlns:w=”urn:schemas-microsoftcom:office:word” xmlns=”http://www.w3.org/TR/REC -html40"> <head> <meta http-equiv=Content-Type content=”text/html; charset=windows-1252"> <meta name=ProgId content=Word.Document> <meta name=Generator content=”Microsoft Word 9"> <link rel=File-List

2. 3.

4.

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Explain how Home Page1.html improves download efficiency. Graphics are important in creating a web page design. Explain why the use of graphics decreases download efficiency. What can be done to reduce this problem?

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HTML DESIGN ELEMENTS

SECTION 8

Hyperlinks HTML was designed as a Hypertext language. That is, HTML could link different text documents. Keywords or phrases can be used to anchor web pages. Hyperlinks allow users to jump or navigate from one anchor to another. All HTML anchors are normally underlined and displayed in blue, which makes them easily recognisable from the rest of the text. Unlike other hypermedia systems, HTML anchors also include the address of the hypertext reference. That is, the anchor also contains the hyperlink itself. The hyperlink contains the new target URL. Look at the following hypertext example: My web page contains information about my pet cat called Kitty. The word ‘Kitty’ is the anchor – it is underlined and displayed in blue on-screen. The HTML document will include the following hyperlink reference script: <a href=“www.me.co.uk/kitty.htm”>Kitty</a> <a></a> defines the anchor. Kitty is the hypertext that can be seen (underlined and in blue) in the web page. The text within the quotes contains the URL address of the target anchor – in this case another web page. Task 26 Answer all of the following questions. 1. 2. 3. 4. 5. 6. 7.

What is a hyperlink? What is hypertext? How are anchors displayed in HTML? Why are anchors displayed differently? What is an anchor? What is contained in an HTML anchor? What is contained in an HTML hyperlink?

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Task 27 Use a simple text editor (like Notepad) and construct a simple website. Your website will have three linked web pages: • Home Page • Sports Page • Interests Page. Site Map Home Page

Sports Page

Interests Page

Home Page Enter the following HTML script:

<html> <head> <title>Home Page</title> </head> <body> Home Page <br> </body> </html>

Save the document as ‘Home.html’. Remember to set the file type to All.

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Sports Page Enter the following HTML script in a new document:

<html> <head> <title>Sports Page</title> </head> <body> Sports Page <br> </body> </html>

Save the document as ‘Sports.html’. Interests Page Enter the following HTML script in a new document:

<html> <head> <title>Interests Page</title> </head> <body> Interests Page <br> </body> </html>

Save the document as ‘Interests.html’. Ensure that the three web pages are in the same folder/directory. Check each web page by displaying them in a browser.

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Display the source code for ‘Home.html’. Edit the code to include the following hyperlinks: <html> <head> <title>Home Page</title> </head> <body> My Home Page <br> <br> <a href = “sports.html”> Sports Page </a> <br> <a href = “interests.html”> Interests Page </a> <br> </body> </html> Save the web page as ‘Home.html’. Display ‘Home.html’ in a browser.

Check out the two hyperlinks. If the hyperlinks do not work, check the file names; it is very easy to have a wrongly named file. For example, ‘Sports.html.txt’ or ‘spots.html’!

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Task 28 Add more text to each of the three web pages.

<BODY> My Home Page <br> <br> I hope that you find my web page interesting.<br> <br> You can click on the following hyperlinks. <br> <a href = “sports.htm”> Sports Page </a> <br> <A href = “interests.htm”> Interests Page </a> <br> </body>

Remember to save the web page before you display it in a browser. The refresh button can be used to reload the page.

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Headings HTML allows the author to set up headings. Header tags can be used to emphasise text. There are six heading tags, <h1> through to <h6>. <h1> is the largest text size; <h6> the smallest. Task 29 Add the highlighted text to ‘Home.html’. Remember to save the page before you display it in a browser. <body> <h1>My Home Page </h1><br> <br> <h2>I hope that you find my web page interesting.</h2> <br> <br> You can click on the following hyper links. <br> <h2> <a href = “sport.html"> Sports Page </a> <br> <a href = “interests.html"> Interest </a> <br> </h2> </body>

Now use the header tags again in ‘Sports.html’ and ‘Interests.html’.

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Fonts HTML allows the author to specify the font that will be used to display the text. The <font> tag can be used to alter the following font attributes: • color • face • size <font color=#FF0000> will cause all text to be displayed in red. <font face = “Times New Roman”> will cause all text to be displayed in Times New Roman face. <font size = 20> will cause text to be displayed in

size 20.

Task 30 1. Add the highlighted HTML script to ‘Home.html’. <h2> <font face=”ALGERIAN”>I hope that you find my web page interesting.</font></h2> <br> 2. 3.

Display ‘Home.html’ in a browser. Edit ‘Home.html’ and change the font size to 20: <h2> <font face=”ALGERIAN” size=20>I hope that you find my web page interesting.</font></h2> <br>

4.

Change the font attributes in ‘Sports.html’ and ‘Interests.html’

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Colours on the WWW All colour definitions use the American spelling of color. The WWW uses the Red Green Blue (RGB) standard of colour control. RGB allows the author to set and change different colour saturations. This is done using a six-digit number: #000000 The first two digits define red: The next two digits define green: The last two digits define blue:

#RR0000 #00GG00 #0000BB

Unfortunately, the WWW does not use the standard decimal number system, but uses hexadecimal numbers! Hexadecimal is a little strange and is based on the number 16, instead of 10.

Decimal 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Hexadecimal 0 1 2 3 4 5 6 7 8 9 A B C D E F

Hexadecimal requires new digits for decimal 10â&#x20AC;&#x201C;15. This is because decimal is base 10, and has zero + nine units, while hexadecimal is base 16, so has zero + 15 units. Binary, meanwhile, is base 2, and has zero + one unit. The WWW uses the hash sign (#) to indicate a hexadecimal number.

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Task 31 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8.

Write down the hexadecimal equivalent Write down the hexadecimal equivalent Write down the hexadecimal equivalent Write down the hexadecimal equivalent What is the decimal equivalent of #B? What is the decimal equivalent of #C? What is the decimal equivalent of #7? What is the decimal equivalent of #2?

of of of of

10. 14. eight. zero.

Setting RGB colours Color (American spelling) RED GREEN BLUE Half RED Half GREEN Half BLUE WHITE BLACK YELLOW MAGENTA CYAN

Hexadecimal Number #FF0000 #00FF00 #0000FF #800000 #008000 #000080 #FFFFFF #000000 #FFFF00 #FF00FF #00FFFF

RGB allows the user to mix the colours. For example, #FF80F0 will produce a very unique colour. Coloured text Adding the following HTML script to ‘Home.html’ will display all body text in red: <body text=#FF0000>

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Task 32 1. Edit ‘Home.html’ to include text=#FF0000. 2. Save web page. 3. Display the web page in a browser. 4. Edit ‘Sports.html’ to include text=#00FF00. 5. Save web page. 6. Display the web page in a browser. 7. Edit ‘Interests.html’ to include text=#0000FF. 8. Save web page. 9. Display the web page in a browser. 10. Experiment with more colours

Coloured background Adding the following HTML script to ‘Home.html’ will display all body text in blue: <body text=#FF0000

bgcolor=#0000FF >

Task 33 1. Edit ‘Home.html’ to include the background colour #0000FF. 2. Save web page. 3. Display the web page in a browser.

Coloured links The WWW allows an author to change the colour of the hyperlink anchors. There are three types of hyperlink: • unvisited link • active link • visited link. An unvisited link is normally shown in blue, indicating that the website or page has not been visited. An active web link (alink) is normally a pale purple colour, showing that the Internet user has selected the anchor and is waiting for the page to be displayed.

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A visited link (vlink) is normally grey, showing that the page has been visited at least once. The following example shows how the author can change the default colours for links. <html> <head> <title>Background colours</title> </head> <body text=#FF0000 bgcolor=#0000FF link=#FF0000 alink=#00FF00 vlink=#0000FF> <a href=”http://www.yahoo.com”>Yahoo</a>

</body> </html>

Task 1. 2. 3. 4. 5. 6. 7.

34 Display ‘Home.html’. Where are the anchors? Edit Home.html to include bgcolor=#000080. Save web page. Display ‘Home.html’. Change the background colours in ‘Sports.html’ and ‘Interests.html’. Experiment further with bgcolor.

Tables Positioning text or images with HTML is problematic. One of the really annoying things about creating a web page is that you cannot guarantee that the page will be displayed the way you intended.

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Different Internet users have different browser software on different computers, which use different types of monitor, all with different resolutions. Also web browser software allows the Internet user to change the text size of the displayed information.

If a web page is being displayed in a window and the Internet user keeps changing the size of the window, then the text and graphics will be continually wrapping around the window. Using the space bar to position text or graphics in the middle of the display screen will have no effect. Browser software ignores all leading spaces, so any carefully positioned text will appear on the left of the display. The best way to solve this problem is to use tables. HTML tables can be used to position text and images and have a similar layout to spreadsheets.

A

B

C

1

A1

B1

C1

2

A2

B2

C2

3

A3

B3

C3

4

A4

B4

C4

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HTML tables deal with rows of information. Each row has many cells and each cell contains table data.

<table> <tr> <td>A1<td>B1<td>C1 </tr> </table>

• The <table> tags set up the table. • The <tr> tag sets up a new table row. All the author needs to do is enter the table data using the <td> tag. The first table data item is A1. The next table data item is B1, etc. Note that the table data is entered in rows. The author can keep entering table data into a row until the row is finally closed with </tr>

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Task 35 Use Notepad to enter the following HTML script: <html> <head> <title> TABLE</title> <body> <b>TABLE</b><br> <br> <table> <tr> <td>A1<td>B1<td>C1 </tr> <tr> <td>A2<td>B2<td>C2 </tr> <tr> <td>A3<td>B3<td>C3 </tr> </table> </body> </html> Save the document as ‘Table.html’. Display the page in a browser. It should look like this:

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Task 36 Tables can be used to position text and images. The following HTML script will allow you to set up a simple menu. Type it into a new Notepad document. <html> <head> <title> TABLE</title> </head> <body> <b>TABLE</b><br> <br> <table border=2 cellspacing=0 cellpadding=5> <caption>MENU</caption> <tr> <td>PAGE 1</td> </tr> <tr> <td>PAGE 2</td> </tr> <tr> <td>PAGE 3</td> </tr> </table> <hr> ©LTSCOTLAND </body> </html> Save the document as ‘Menu.html’. Display it in a browser. It should look like this:

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Borders In Task 36 (previous page), the HTML script contains the tags border, cellspacing, cellpadding and hr. • sets the width of the border. If BORDER=0 then no border is displayed. • CELLSPACING sets the gap between the cells. • CELLPADDING sets the size of the gap between the table data and the border. • The <HR> tag creates a horizontal rule across the web page. Tables can also be used to position graphics and text. The HTML script shown below displays text and a graphic inside a table. Task 37 Use Notepad to add the following HTML script to a new document. The graphic ‘Train.jpg’ should be copied and pasted into your working directory. (That is, this file and ‘Train.jpg’ must be in the same directory.) <HTML> <HEAD> <TITLE> LAYOUT TABLE</TITLE> </head> <BODY> <B>TABLE ARE USED TO DEFINE LAYOUT</B><BR> SET BORDER SIZE TO ZERO<BR> <BR> <TABLE BORDER=2 CELLSPACING=5 CELLPADDING=10> <TR> <TD>STEAM TRAIN <TD><IMG SRC=”TRAIN.JPG”> </TR> <TR> <TD>A2 <TD>B2 </TR> </TABLE> </BODY> </HTML> Save the web page as ‘Train.html’. Display the page in a browser. 104

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Set border size to Zero

Go back into the file and edit the table definitions so that the border becomes invisible. NB: To include any graphical images in a web page, the author needs to set up a hyperlink to the source image, e.g. <img src=“TRAIN.JPG”>

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Meta data The <meta> tag contains information about the web page/site and is situated inside the header tags.

<html> <head> <title>Home Page</title> <meta> </head> <body> This is my Home Page </body> </html>

Search engines search through the <meta> tags for information about the website. For instance: <meta name=“KEYWORDS” value=“computers,database,web design,HTML”> The <meta> tag informs search engine web spiders that the website is about “computers and databases and web design and HTML”. The search engine will then index the website using these keywords.

Task 38 Answer the following questions. 1. 2.

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Where are <meta> tags located in the HTML structure? How are <meta> tags used by search engines?

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SECTION 9

In addition to overall legibility, good website design should consider the following: • • • • • • •

visual balance consistency page dimensions emphasis headers and footers page layout download efficiency.

Visual balance The human eye will first see a web page as a mass of colour with a contrasting foreground and background. Next, a user will begin to see the information as the web page. Usually, the user will take in the graphical information and then the textual information, reading from the top left corner of the page. A page of solid text is uninteresting and may not catch the reader’s attention. World Wide Web Although hypertext systems have been in use for many years, it was the development of HTML by Timothy Berners-Lee that allowed everyone to put information onto the web. Timothy coined the phrase “World Wide Web”. Prior to HTML, information could only be placed on WAN using complicated code. HTML is a scripted language which is easy to understand and easy to use.

This next example is better, using colours and a horizontal rule to break up the page.

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World Wide Web Although hypertext systems have been in use for many years, it was the development of HTML by Timothy Berners-Lee that allowed everyone to put information onto the web. Timothy coined the phrase “World Wide Web”. Prior to HTML, information could only be placed on WAN using complicated code. HTML is a scripted language which is easy to understand and easy to use.

The next version has menus on the left, and this helps the eye to flow from top left to bottom right.

World Wide Web Menu HTML HTTP POP SMTP

Although hypertext systems have been in use for many years, it was the development of HTML by Timothy Berners-Lee that allowed everyone to put information onto the web. Timothy coined the phrase “World Wide Web”. Prior to HTML, information could only be placed on WAN using complicated code. HTML is a scripted language which is easy to understand and easy to use.

Good web design requires careful balance between text and graphics, so as to lead the user through the content.

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Line length Remember that the human eye has a comfort zone! This is the length of a line of text that the eye can take in without the eye muscles needing to readjust. A long line of text often requires the reader to hunt for the beginning of the next line. Traditionally, the optimum line length in books has been considered as 66 characters. For web page design, the use of tables can help increase readability.

Margins Margins are very important, as they actually define the reading area. Well-defined margins give contrast between the text and other graphical elements.

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Consistency A consistent layout allows readers to quickly understand what is happening and how to navigate from one web page to another without getting disorientated.

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Page dimensions Page width Web pages and printed documents have many similarities, but it must be remembered that web pages are displayed on a screen and, if an A4 document is displayed in a browser, then the right hand margin will be lost. Screen Area

Although hypertext systems have been in use for many years, it was the development of HTML by Timothy Berners-Lee that allowed everyone to put information onto the web. Timothy coined the phrase “World Wide Web”. Prior to HTML, information could only be placed on WAN using complicated code.

V

V

HTML is a scripted language which is easy to understand and easy to use.

Document Area

It is a common fault in web design to increase the line length of the web page beyond the normal viewing area. The Internet user needs to use the horizontal scroll bar in order to read the text. He/she needs to scroll right to see the missing text and then scroll left to get back to the start of the next line. If the Internet user wishes to print the web document, the text on the right-hand side will not be printed; it will be cut off. This can be infuriating! Page length Web page design needs to take account of: • web page versus screen size • web page content.

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Web page versus screen size A long web page requires the Internet user to scroll up and down through the document. The Internet user may become disorientated. Many long web pages use links, which allow the user to jump to the start of the desired section of the page, and also to jump back to the top of the page. Web page content It is best to keep related information on a single page. Try and keep the web page content to no more than two printed pages. It is best to favour short web pages for: • home pages • documents that will be read online • pages that contain lots of graphics.

Task 39 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

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List the seven good web design properties. Explain why contrast is important in web page design. Explain why good web design requires good visual balance. Explain what is meant by the human eye having a ‘comfort zone’. Explain why long line length causes readers problems. Why are margins important? What problems may occur when a printed document is displayed in a web browser? Explain how an Internet user can display the information in a long web page. Why is it important to display a ‘top’ hyperlink at the foot of a long web page? List three occasions when short web pages are particularly favourable.

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Emphasis A web page that contains solid text is very difficult to read and understand. Italics, bold and colour can be used to emphasise important facts, but these elements should be used sparingly. Italics Text that is displayed in italics attracts the eye, as it is contrasted against the rest of the text. Bold Bold text stands out from the rest of the text. Underline Underlines should be avoided at all costs, as web pages use underlining specifically to display anchors. Colour Colour is a good way of emphasising text, but care must be taken if colour is used inside a text block, as it may appear to be an anchor leading to a hyperlink. Colour works well if it is used to distinguish headings and sub-headings. Upper case Upper-case text is fine in headings and sub-headings, but body text is very difficult to read if it is displayed in upper case.

WORLD WIDE WEB ALTHOUGH HYPERTEXT SYSTEMS HAVE BEEN IN USE FOR MANY YEARS, IT WAS THE DEVELOPMENT OF HTML BY TIMOTHY BERNERS-LEE THAT ALLOWED EVERYONE TO PUT INFORMATION ONTO THE WEB. TIMOTHY COINED THE PHRASE “WORLD WIDE WEB”. PRIOR TO HTML, INFORMATION COULD ONLY BE PLACED ON WAN USING COMPLICATED CODE. HTML IS A SCRIPTED LANGUAGE WHICH IS EASY TO UNDERSTAND AND EASY TO USE.

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Headers and footers The page header plays an important role in stimulating interest in the site. Efficient web-page design should display a number of different interactive options within the top few inches of the page. A good header graphic will also help give the website a unique identity. Each web page should contain information about the author, and when the page was created. The footer is usually used to display this information. Footers are also very useful if a long web page has been created. If the navigation links are all at the top of the web-page and no longer visible, the footer could contain a link that returns the user to the top of the page.

Page layout It is impossible to have total control over web-page layout. Unlike a paper document, which is a fixed layout, a web page has a flexible layout. Web pages need to cater for different: • • • • • • •

screen display sizes resolutions colour depth browser types user preferences available fonts users changing the window size.

Using meta tags HTML meta tags should contain keyword information about the website. After all, what is the point of designing and creating a website if no-one is going to visit? But what should be entered as keywords? Use words that you would expect Internet users to know and use. There is little point in using phrases like ‘vacuum energy’ or ‘interstellar

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gravitational energy constant’ when the user is more likely to search for ‘outer space’. Keep it simple.

Things to avoid When designing a web page, the following should be avoided: • • • • • • •

frames using new technology scrolling text complicated URLs orphan pages lack of navigational support using non-standard anchor colours.

Frames Frames split the browser window into different sections. Frames may look good, but they can be a nightmare for authors and users alike: book-marking the web page does not work, while some URLs stop working altogether; hardcopy printouts can be a disaster. This is because a page with frames is really just a display of several different linked pages. New technology You may have the latest technology, and have access to the latest browser software versions, but will your target audience have access to the same technology? Continual error messages will discourage visitors to your hi-tech website! Complicated URLs URLs should contain readable directory names and file names. Which of the following do you find easier to understand? http://www.mywebsite.org.uk/science/chemistry/sweeteners/sugar.html http://www.mywebsite.org.uk/subjectlevel1/subjectlevel2/ssss/ document15a.html

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Orphan pages An orphan page is one without any links to another page. If someone uses a search engine link to an orphan page, they can’t access any more of the website. So, it is important that all web pages have a clear indication of their location within the website. Each web page should have a link to the website home page. Lack of navigational support Remember that visitors do not know as much as you do about your website. The simplest way to give help to visitors in navigating through your website is to include a user-friendly site map. Using non-standard anchor colours Keep to the standard blue, grey and magenta anchor colours. Visitors are familiar with these colours; and so they have an immediate understanding of them. Anchor colours are one of the few navigation aids that are standard on most browsers.

Download efficiency The issue of download efficiency has already been mentioned with respect to HTML script size and multimedia files. Graphics and sound certainly make a website interesting, but care must be taken to balance the number of images against the time needed to transmit the images. There is nothing worse than sitting waiting for a number of images to finally appear in the browser. Flash animations can be a particular source of annoyance. Good web-page design needs to take into account: • the amount of HTML script needed to create the web page • the number of linked multimedia files in the web page.

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Uniformity of presentation Good website design requires a uniform presentation, with each web page laid out in a similar manner, giving the Internet user a predictable, familiar environment. If a website consists of web pages that all have different layouts and backgrounds, the user may become disorientated and unable to navigate successfully through the website. The following table template is a recognised standard for web-page design.

Header

Content area

V

V

Left margin used to display menu options, links, adverts, etc.

V

Line length should be equivalent to the eye’s comfort zone

Gutter margin used to separate the left margin contents from the main content area.

Footer

The top three or four inches of a web page are of prime importance – this area is displayed first. Most modern web page designs use the header area and the top content area for maximum visual impact, and to display hyperlinks. Header titles make maximum impact if the title is left justified, thus leading the eye towards the content area.

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Header

Left margin often used to display menu options...

Content area

Footer

The footer should be used to display copyright information and, with long web pages, to provide a means of returning to the top of the web page. Use contrasts to emphasise the page content.

Header

Left margin often used to display menu options

Content area

Footer

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Browser compatibility issues We have all seen browser display errors. What causes these? Web browsers interpret HTML script so that the web page can be displayed in a window. Different browsers interpret these scripts differently. W3C defines HTML standards, but these standards offer a considerable amount of leeway in their implementation. For example, W3C defines table tags, but no default values for cellspacing. So, different browsers might use different default cellspacing. If you donâ&#x20AC;&#x2122;t specify the spacing, it might display differently in another browser. Browser versions Different versions of the same browser also cause problems. It takes time for Internet users to update to the latest version of their software. Creating web pages that can only be displayed on the latest version will limit the number of users who can view your page. Platforms Different computer platforms use different browser software, operating systems, etc. An Apple Mac will display fonts 2 points smaller than a PC, and it will use different font style names. You should try to view your web pages using as many different browsers and computer types as possible, to check that your pages appear OK under most conditions. Here are some standard fonts: PC

MAC

Arial

Charcola

Courier

Chicago

Courier New

Courier

Times New Roman

Palatino

MS Sans Serif

Geneva

MS Serif

Helvetica

Times New Roman

Monaco

Verdana

New York

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Task 40 Answer all the questions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

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Why must colour inside a text block be used carefully? When does colour work best in a web page? Why should a block of text never be displayed in upper case? Why are web-page headers so important? Why are good header graphics important? What should be contained in web-page footer? Explain the difference between a fixed and a flexible page structure. Which structure best suits web-page design? Why is the underlying web-page design important? What are keywords and why are they important? Explain why the use of frames should be avoided. Why should web pages not contain the latest technology? Why should URLs not contain complicated structures? What is meant by ‘different browsers interpret HTML scripts differently’? What problems may occur if different versions of the same browser software are used to display a web page?

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UPLOADING AND PUBLISHING WEB PAGES

SECTION 10

Once a website has been created, it needs to be uploaded to the web server so that it can be published on the WWW. Most ISPs and Internet companies, such as Yahoo and Lycos, offer Internet users free web space. Once the Internet user has subscribed to an ISP or Internet company, then he/she will be able to upload a website. To do this, the Internet user needs to use FTP software, which will copy the website from the author’s hard drive to the host web server.

FTP software IPswitch is one commonly used FTP package. There are many others. Nowadays, most authoring applications contain FTP tools.

In order to upload files from the user’s computer to the host, the author needs to display the website files that are stored on his/her computer. Next, the author needs to select the files to be uploaded and click on the upload/download arrows, which are displayed in the centre of the FTP window.

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Internet companies (such as Lycos) offer their own FTP system, which can be used to upload a website.

Levels and URL It is essential that the top-level page of an active website be titled index. When a URL, such as http://www.mywebsite.co.uk is entered into the browser address bar, the web server defaults to http:// www.mywebsite.co.uk/index... (Note that the file extension will depend on the requirements of the host and the format of the web document – we are using .html here. Another example you might come across is .asp.) If the following website were uploaded, then entering http:// www.mywebsite.co.uk would not work, as the top-level web page is ‘home.html’.

Home.html

Sports.html

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Interests.html

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If the following website were uploaded, then http:// www.mywebsite.co.uk would work, as the top-level page is titled ‘index.html’.

index.html

Sports.html

Interests.html

Task 41 Answer the following questions. 1. 2. 3. 4.

Which type of software is needed to upload a website? What does uploading mean? Why does FTP software upload a copy of the website? Why must the top-level file in a website be renamed ‘index’?

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SECTION 11

The WWW uses HTML and HTTP to provide services between client and server. But many of the web pages that you will have viewed are dynamic and interactive. HTML cannot support these features. HTML is static. Once the web page has been downloaded and displayed in the browser, it cannot be changed. In order to make web pages dynamic, the author must write client-side scripts. <html> <head> <title>Home Page</title> <meta> <script></script> </head> <body> Text and <script></script> </body> </html> Client-side scripts can be located in the header or in parts of the body. Client-side scripts are programmes that run on the client’s computer. JavaScript VBScript

CGI PHP MySQL Hit counters

Client side

Server side

Most Internet browsers can interpret JavaScript and VBScript, which are scripting languages.

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JavaScript

VBScript

<html> <head> <title> JavaScript Test </title>

<html> <head> <title> VBScript Test </title>

<script language=“JavaScript”>

<script language=“VBScript”>

alert(“Welcome to JavaScript”)

msgbox “Welcome to VBScript”

</script>

</script>

</head>

<head>

<body> This is HTML </body> </html>

<body> This is HTML </body> </html>

The <script> tags define where the client-side script is going to be placed. The tag needs the LANGUAGE attribute, which will define the scripting language to be used. Alert messages JavaScript uses alert( ) to display or alert the Internet user, while VBScript uses msgbox (Message Box) to do the same task.

Task 42 1. Enter the JavaScript version above into Notepad. Ensure that alert( ) is entered in lower case. 2. Save web page as ‘java.html’. 3. Display the page in a browser. 4. Enter the VBScript version above into Notepad. Ensure that there is a space between msgbox and “Welcome to VBScript”. 5. Save web page as ‘vbscript.html’. 6. Display the page in a browser.

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Problems with JavaScript If you are using Internet Explorer, you may have difficulty getting JavaScript to work. You may need to change the Internet Options / Advanced features in your browser and select Java Console enabled.

NB: If JavaScript does not work on your school computer system, then just complete the VBScript tasks. If you are using a Mac, then VBScript may not be available.

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Dynamic web-page design Client-side scripting allows the author to create dynamic web pages. Dynamic web pages can be used to display ever-changing information. Dynamic web pages depend upon the Document.Write command. This needs to be included in the script that makes up the web page. Each time the web page is downloaded, the Document.Write command is executed, creating its own unique piece of HTML script. This might not appear to be much of an advantage, but the script can include dynamic data, such as today’s date. Using JavaScript or VBScript, the date will update automatically every time the page is downloaded.

JavaScript

VBScript

<html> <head> <title>JAVADATE</title>

<html> <head> <title>VBDATE</title>

<script language="JAVASCRIPT">

<script language="VBScript">

today =new Date() document.write("<h1>Hello. Todays date is" + today + "</h1>");

document.write "<h1>Hello. Todays date is " & date() & "</h1>"

</script>

</script>

</head> <body>

</head> <body>

Welcome

Welcome

</body> </html>

</body> </html>

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Task 43 1. Enter the JavaScript version above into a text editor. 2. Save the document as ‘Java Date.html’. 3. Display the page in a browser. 4. Enter the VBScript version into a text editor. 5. Save the document as ‘VBS Date.html’. 6. Display the page in a browser. 7. Edit ‘VBS Date.html’ to include the following: document.write "<h1>Hello. Todays date is " & date() & time() & "</h1>" 8. 9.

Save the document as ‘VBS Date.html’. Display ‘VBS date.html’ in a browser.

Cookies Cookies allow a web server to send and receive information. A cookie is a text file that contains one line of text, and which is stored on the web server or the user’s hard drive. If you visit a website that has a hit counter, then your browser software will check to see if you have already visited the website. Your browser will look into the Cookies folder to check if the website has already stored a hit counter cookie. If the Cookies folder does not have a cookie from the website, then the browser sends a cookie to the website, requesting that the hit counter be increased by one. Once the value of the counter has been increased, the web server sends a cookie to the browser. The browser stores the hit counter cookie in the Cookies folder and the hit counter value is displayed in the browser. Cookies and databases Web-based companies, especially e-commerce, make a lot of use of cookies and underlying databases. Cookies allow the client’s browser to exchange information with the web server. Have you ever purchased CDs or books or holidays using the Internet?

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Internet companies use databases, especially relational databases, to store and process personal information. If you book a low-cost flight on the Internet, your details and the flight details are stored on the company’s database. If you want to purchase a book or a holiday using the Internet, then you will query a server-side database to check if the book or holiday is available.

It is important to remember that e-commerce is really about data processing. Some of the data is personal data about the client, while the remaining data contains stock details. All this information will be held on web-based databases. These are large databases, most likely relational databases, which are situated on the host’s web server. On-line shopping uses cookies to keep track of a customer’s order. Every time a customer selects an item, a cookie is sent to the server. The cookie is then used to update a web-based database, which contains the client’s shopping list. In turn, the server sends the client a cookie confirming the purchase. There are other types of web-based databases, some of which are fun to use!

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Check out the Internet Movie Database: www.imdb.com Cookie privacy The interchange of cookies is invisible. The client has no idea that information about them is being sent by the browser to the web server. Your browser will allow you to set how you want to interact with cookies. Internet Options will allow you to restrict the number and type of cookies that are sent to and from the web server.

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Document.cookie Document.cookie allows client-side script to interact with cookies. However, it requires communication between the client’s browser and a web server, and this means that it might not work on a standalone computer system or school system that does not support a web server. You can download your own web server from: http://www.keyfocus.net Look at the following client-side script:

<html> <head> <title>Cookies</title> <script language=“VBScript”> if document.cookie=“” then user= inputbox(“ENTER YOUR NAME”) document.cookie=USER else user=document.cookie end if document.write “<h1> HELLO ” & user & “HOW ARE YOU?</h1>” </script> </head> <body> <p> User’s name will be displayed in the heading Once the user’s name has been stored as a cookie then his/ her name will appear automatically. </p> </body> </html>

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Task 44 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8. 9.

What do cookies allow web servers to do? What is contained in a cookie? Explain how hit counters use cookies. What are web-based databases? What type of database structure is used by web-based databases? Explain how cookies and web-based databases are used to purchase goods over the Internet. What is meant by the invisible interchange of cookies? Explain how you can safeguard your cookie privacy. Why will document.cookie not run on a standalone computer system?

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Submission forms One way of using web pages to collect information is to use a submission form.

<html> <head> <title>Sub Form</title> <script language="VBSCRIPT"> </script> </head> <body> <h1>Welcome to Scotland Stores</h1> <br> <form method=post action="mailto:your email address"> First name...... <input Name=Firstname type=Text><br> Surname ........ <input Name=Surname type=Text><br> E-mail address <input Name =Email type=Text><br> <br> <input type=submit value="SEND NOW"> </form> </body> </html>

The <form> tags set out where the submission form will be displayed in the browser. The tag can also contain a methodof returning the collected information. In this case, the collected information will be posted, that is e-mailed to you using action:mailto followed by your e-mail address. Task 45 1. Enter the HTML script above into Notepad. 2. Save the document as ‘Sub Form.html’. 3. Display the page in a browser. 4. Enter your own details into the submission form and click on SEND NOW.

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This method of collecting data is not very reliable, nor is it secure. Originally, only Netscape allowed mailto: so you may have difficulty getting it to work with Internet Explorer. Internet Explorer might display a warning message explaining that your e-mail address will also be sent, or your school network might refuse to handle mailto: Fortunately, there are better ways of collecting information from a submission form. However, this requires your web server to have access to a CGI bin. A CGI bin is a special directory that allows the user to store information. It requires management software to analyse the collected data. <form method=post action="www.domain.co.uk/cgi_bin/formmail/"> <input type=hidden recipient="your email address"> First name...... <input Name=Firstname type=Text><br> Surname ........ <input Name=Surname type=Text><br> E-mail address <input Name =Email type=Text><br> <br> <input type=submit value="SEND NOW"> </form>

This method will probably not work on your school computer system, but most ISPs offer web tools, allowing you to set up a CGI bin.

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Form validation Form validation requires that the data in the submission form has been entered correctly. The VBScript program does a simple validation check to ensure that required/compulsory fields have not been left blank. 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360

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<html> <head> <title>Validation </title> <script language=”VBSCRIPT”> Private Sub Button_onclick() <!– – Validation Check – –> IF len(customer.Firstname.value)= 0 or len(customer.Surname.value)= 0 then msgbox "Error!" else msgbox "Data ready to be submitted" <!– – Write a CGI_bin routine to send data – – > end if end sub </script> </head> <body> <h1>Welcome to Scotland Stores</h1> <br> <form name=CUSTOMER> First name*...... <input Name=Firstname type=Text><br> Surname* ........ <input Name=Surname type=Text><br> E-mail address <input Name =Email type=text><br> <br> <input name=button type=submit value="SEND NOW"> <p> All data items mark* as required. </p> </form> </body> </html>

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CLIENT-SIDE SCRIPTING

The Private Sub Button_onclick() sub-routine is executed when the SEND NOW button is selected, or ONCLICK. In lines 90–120, the length of the first name and surname is checked. If either the first name or surnames have not been completed, then the number of letters in the name will be ZERO. If either name has not been completed, an error message will be displayed, but if the first name and surname have been completed, the data is ready for transmission to cgi_bin.

Task 46 1. Edit ‘Sub Form.html’ to include the extra VBScript needed for form validation. 2. Save the web page as ‘Sub Form.html’. 3. Display the page in a browser. 4. Select SEND NOW without entering any data. 5. Select SEND NOW after entering your own details.

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Task 47 1. Edit ‘Sub Form.html’: delete line msgbox "Error!" and replace with the script shown below. This script will alert the user about the actual information that they have missed. if len(customer.Firstname.value)= 0 then msgbox "First name has not been completed" End If if len(customer.Surname.value)= 0 then msgbox "Surname has not been completed" End If 2.

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Write VBScript to ensure that the e-mail address has not been omitted.

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Task 48 1. Construct your own submission form for ‘Super Store’. Use the previous example as a template. The Super Store web page must contain: • • • •

date and time – use document.write three required fields* form validation to ensure that the fields are not left blank alert messages notifying the user which fields have not been completed • headings <h1>… 2.

Change text and background colour; show off; have some fun! What about a couple of graphics? Save web page as ‘SuperStores.html’.

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SERVER-SIDE SCRIPTING

SECTION 12

PHP/MySQL PHP stands for Pre-Processed Hypertext. However, PPH does not look as catchy as PHP! PHP is a server-side scripting language. That is, web pages that contain PHP script are executed on the web server and the output is transmitted to the client.

Server side PHP

Date is 16 January 2004 Client side

PHP has many advantages over client-side HTML and VBScript/JavaScript methods: • Transmitted web page documents are reduced in size, as PHP output is sent instead of large amounts of HTML script. • No need for client-side plug-ins. The PHP script is executed on the web server, so only the web server needs plug-ins. • Browser software should not need continual updating. The updates only need to affect the web server. PHP has one obvious disadvantage, namely the slowing down of the web server while it executes PHP script. PHP and MySQL work together on the web server. MySQL is a standard query language, which is used to store and interrogate data that has been collected on the Internet.

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E-commerce is totally dependent upon PHP/MySQL. If you book a flight or purchase goods over the Internet, there will be a MySQL database storing your details and processing your order. Check out: http://www.ryanair.co.uk This is one of the more user-friendly flight booking systems on the Internet. Please do not book any flights!

Task 49 Answer the following questions. 1. 2. 3. 4. 5. 6. 7.

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What is the correct name for PHP? What is PHP? What is sent from the web server? List the advantages of using PHP. What is the major disadvantage? Which web-based industry is totally dependent upon PHP/ MySQL? Explain how the World Wide Web and relational databases work together so that you can purchase a book on the Internet.

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CASCADING STYLE SHEETS

SECTION 13

Style sheets Style sheets are definitions – sets of rules – for a number of text formatting controls. HTML lacks any control over the way that text is displayed in a web page. The W3C recommendation for cascading style sheets (CSS) allowed authors to define their own text styles and incorporate these styles into their web pages. For example, the standard <h1> headings tag normally uses the Arial font to display text. If an author decides to use Times New Roman for a website, then he/she needs to change the <h1> tag on every web page. If the website has a couple of hundred web pages, that might prove daunting! A style sheet allows an author to set up a style that can be linked to all of the web-page documents.

Style Sheets

Setting up a style sheet The following style-sheet definition will change the <h1> headings tag to display all text in Times New Roman: h1 {font-style: Times New Roman} Style sheets are saved as simple text files, with a .css extension.

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CSS recommendations The W3C consortium has issued the following three sets of recommendations. December 1996 CSS1 Style properties Fonts Text Box Colour/color

May 1998 CSS2

Media Position properties Download format Table styles Text shadowing

January 1999 CSS3 User interface Scalable vector graphics Multimedia

For more information on W3C recommendations, check out: www.w3.org/Style/ Style sheets offer the following advantages: 1. 2. 3.

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web pages are more concise and less cluttered style sheets are flexible one individual style sheet can be used in many different web pages.

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Task 50 Answer the following questions. 1. 2. 3. 4. 5. 6. 7. 8.

What are style sheets? What does HTML lack? What is the name of the body that makes style-sheet recommendations? If an author wants to change the font in the <h1> tag, what would they need to do? How many style sheets are needed to change the display of a website? How are style sheets saved? How many W3C recommendations have been made? List the advantages of using a style sheet.

Creating a cascading style sheet Use Notepad, or any other text editor software, to enter the following text: h1 {color: red} body {background-color: green} Save the style sheet as ‘style1.css’. That’s all there is to it! The inclusion of this style sheet into any web page will display a green background and all <h1> tags in red. Inserting CSS into a web page There are three ways of including a style sheet in an HTML web page: • embed the style sheet into the <head> area • link or import a saved .css file • attach a .css definition to a section of an HTML web document.

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Embedding style sheets Embedded style-sheet definitions are located in the <head> area of the HTML web-page document.

<html> <head> <title> Style Sheet </title> <style type=”text/css”> <! - -h 1 {color: red} -->

</style> </head> <body> <h1> Red Heading</h1> <p>This is a test</p> </body> </html>

Task 51 1. Use text editor software to enter the script given above. 2. Save the document as ‘red test.html’. 3. Display ‘red text.html’ in a browser. The embedded style redefines the <h1> tag so that all text is displayed in red. 4. Change <style> to display <h1> in blue. 5. Change the text ‘Red heading’ to ‘Blue heading’. 6. Save as ‘blue text.html’. 7. Display ‘blue text.html’ in a browser.

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Linking or importing style sheets Most web browser application software allows the linking of .css files to web pages. The file is linked to the web page in the same way as an image file is linked. Style sheet:h 1 {color: red} Web page text:

<html> <head> <title> Style Sheet </title> <link rel=”stylesheet” href =”red.css” type=”text/css”> </head> <body> <h1> Red Heading</h1> <p>This is a test</p> </body> </html>

Task 52 1. Use text editor software to enter the style sheet text shown above. 2. Save as ‘red.css’. 3. Use text editor software to enter the HTML script above. 4. Save as ‘red link.html’. 5. Display ‘red link.html’ in a web browser.

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Importing style sheets As the name suggests, a .css file is imported into the web page document. Style sheet text: h1 {color: red} Web page text:

<html> <head> <title> Style Sheet </title> @import url(red.css); </head> <body> <h1> Red Heading</h1> <p>This is a test</p> </body> </html>

Task 53 1. Use text editor software to enter the style sheet text shown above (or use the saved ‘red.css’ style sheet). 2. Save as ‘red.css’. 3. Use text editor software to enter the HTML script above. 4. Save as ‘red import.html’. 5. If you have Internet Explorer 6 (or equivalent), display ‘red link.html’ in a web browser. NB: Internet Explorer 5 or below will not allow @import url linking of style sheets.

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Attaching a CSS definition Attaching a CSS definition allows the style definition to be directly attached to the HTML tag. Web page text:

<html> <head> <title> Style Sheet </title> </head> <body> <h1 STYLE=”color: red”> Red Heading</h1> <p>This is a test</p> </body> </html>

Task 54 1. Use text editor software to enter the HTML script above. 2. Save as ‘red apply.html’. 3. Display ‘red.apply.html’ in a browser.

Conflicts and cascading What happens when the same style sheet rules have been entered more than once? For example: h1 {font-style: Times New Roman} h1 {font-style: Courier} The first rule changes <h1> to Times New Roman, while the second rule changes <h1> to Courier. These rules are in conflict – but cascading will resolve the conflict. Cascading will ignore the first rule and execute the second rule.

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Cascading is like a waterfall: as each similar rule is listed down through the style sheet, the last rule encountered will be executed and all previous similar rules will be ignored.

Task 55 Answer the following questions. 1. 2. 3. 4. 5. 6.

What are the three methods of using cascading style sheets? Where must all embedded style sheets be entered? Name the two methods of including separate style sheet files. What problem is associated with @import? What does cascading deal with? Explain how cascading deals with the following conflict: h1 {font-style: Times New Roman} h1 {font-style: Courier}

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Task 56 Use Microsoft Word, or any other web-authoring package, to create the following web-page document.

1. 2. 3.

Use <h1>, <h2>, <h3> to display the text. Save as ‘heading.html’. Use a text editor, such as Notepad, and create the following style sheet: h1 {color: red} h2 {color: blue} h3 {color:green}

4. 5. 6. 7. 8. 9.

Save the style sheet as ‘heading.css’. Ensure that ‘heading.html’ and ‘heading.css’ are in the same directory. Display ‘heading.html’ in a browser. Use View/Source to display the HTML script. Delete any script within the <script></script> tags. Now enter the following script into the <style></style> tags: <!— <link rel=”stylesheet” href = “heading.css” type=”text/css”> —>

10. 11.

Save as ‘heading.html’. Display ‘heading.html’ in a browser. The web page should display the three headings in different colours.

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Setting up cascading style sheets Cascading has three basic rules: 1. 2. 3.

The most specific rule applies. If rules have the same specification, then the last rule will be executed. Embedded rules are over-ruled by linked or imported rules.

If you have access to Visual Basic, then you should also have access to Microsoft Development Environment.

Development Environment allows the user to create cascading style sheets. It supplies the user with a list of fonts and the HTML tags that can be used to create quite complicated style sheets. If you do not have access to Microsoft Development Environment, then you can always create style sheets using Notepad or any other text editor. Remember to save the style sheet with the .css extension and, of course, set the Save type to All. Specialised web-authoring packages, such as Dreamweaver, devote a lot of resources to the creation and management of CSS.

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CASCADING STYLE SHEETS

Task 57 1. Use a text editor and create the following CSS. p { color: magenta } h1 { color: red } h2 { color: green; font-family: ‘Californian FB’ } body { border-right: fuchsia solid; border-top: fuchsia solid; border-left: fuchsia solid; border-bottom: fuchsia solid; font-family: Andy; background-color: lime } 2. 3. 4. 5. 6.

Save as ‘Classic.css’. Link or import ‘Classic.css’ into ‘SuperStore.html’. Display ‘SuperStore.html’ in a browser. Edit ‘classic.css’ to include other fonts and sizes. Display ‘SuperStore.html’ again, and notice how it has changed.

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CASCADING STYLE SHEETS

CSS definitions The following CSS definitions can be used with the <h1>...<h6>, <body>,<p> tags.

CSS Fonts

Text

Box

Colour

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font-family font-size font-style font-variant font-style font-weight text-align text-indent word-spacing border border-color border-style border-width color #RRGGBB background-color background-image

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PRACTICAL TASK AND CHECKLIST

SECTION 14

Outcome 2 To complete Outcome 2, you are required to demonstrate the following practical skills: • • • •

use of HTML coding (including layout tables) in web-page design use of client-sided scripting in web-page design use a cascading style sheet in website design creation of web pages, forming a multi-page website with links to other pages on the same site.

The following task gives you the opportunity to demonstrate all of these skills. Remember that you must produce hard copy evidence of two of the skills listed above.

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PRACTICAL TASK AND CHECKLIST

Outcome 2 – Budget Airways 1.

Create the following HTML website.

Site map Budget Airways Home Page.html

Glasgow Departures.html

Edinburgh Departures.html

Dublin Departures.html

Booking Form.html

Your website’s top level is the Budget Airways Home Page. The text for this is shown below.

Welcome to Budget Airways Welcome to Budget Airways. We offer the best low-cost fares from any of the following national and international airports:

Glasgow

Edinburgh

Dublin

Simply select the airport of your choice.

2.

3.

156

Create and save ‘Budget Airways Home Page.html’. Remember that the home page needs to grab the Internet user’s attention, so use lots of colour and embed some graphical images. Create ‘Glasgow Departures.html’, using the text shown below. You must use <table> tags to help construct the page.

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PRACTICAL TASK AND CHECKLIST

Budget Airways – Glasgow Departures Flight Number BD 9777 BD 9779 BD 9781 BD 8001 BD 8021

Destination EDINBURGH DUBLIN INVERNESS BOURNEMOUTH LUTON

Edinburgh Departures

Date 12/04/2004 12/04/2004 13/04/2004 13/04/2004 13/04/2004

Time 10:00 14:20 09:35 10:20 15:45

Dublin Departures

Book your flight

4. 5. 6.

Save as ‘Glasgow Departures.html’. Edit the file to embed a graphic of an aeroplane; use <H1>…<H6> to improve the headings. Create two new web pages: • Edinburgh Departures.html • Dublin Departures.html

7.

8.

Use the same layout as ‘Glasgow Departures.html’ for the two new pages. Enter your own flight numbers, destinations, dates and times. Hyperlink ‘Budget Airways Home Page.html’ to each of the following web pages: • Glasgow Departures.html • Edinburgh Departures.html • Dublin Departures.html

9.

Create ‘Booking Form.html’ from the text shown on the next page.

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PRACTICAL TASK AND CHECKLIST

Budget Airways – Booking Form Date 24/04/2005 Flight Details Departure Airport Arrival Airport Date of Departure

Customer Details Surname First name Title Address Town Post Code

Submit Booking

10.

11.

Use client-side script to validate all entries to ensure that no entry has been omitted. Display alert messages indicating which fields have been left blank. Hyperlink ‘Budget Airways Booking Form.html’ to each of the following web pages: • Glasgow Departures.html • Edinburgh Departures.html • Dublin Departures.html

12.

158

Use one simple cascading style sheet to set up the font style and colours for all the web pages.

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PRACTICAL TASK AND CHECKLIST

Information Systems: The Internet Unit (Higher) Observation checklist Student name: Starting date of assessment:

Budget Airways Practical skill

Completed

Use of HTML script Use of color and bgcolor Use of <h1>…<h6> Use of embedded images Correct use of table definitions Data entered into tables Creation of submission form Client-sided script used to validate submission form entries Creation of alert messages Creation of cascading style sheet Linking or importing CSS into web pages Creation of a multiple-page website All hyperlinks working correctly

Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No Yes/No

Pass Fail

Completion date: Tutor’s signature:

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APPENDIX: HTML TAGS

APPENDIX

HTML tags Tags < ! ... comment ...> <a href = “url”> </a>

<address> </address> <b> </b <base href= ...> <blink> </blink> <body></body

<caption> </caption>

<center> </center> <cite> </cite> <code> </code> <dd> <div> <dl> </dl> <dt>

Description Not displayed in browser window Hypertext link to local or remote url target =Name target =_self target =_parent target =_blank href options to specify how a document is to be displayed Holds author’s e-mail address Bold text Sets the base url. Use when files are stored in a set of folders and sub-folders Make text flash on and off Defines body area background = Image filename bgcolor = Colour number ... Note color spelling!! text = Colour number to change text colour link = Colour number to set link colour vlink = Colour number to set visited site colour link alink = Colour number to set active link colour Define caption align=top align=bottom Centre text or image Citation Source code Document definition Text formatting command Define a list Term in a definition list

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APPENDIX: HTML TAGS

<font ...> </font>

<form> </form>

<frameset...>

</frameset> <head> </head> <hn> </hn> <hr>

<html> </html> <i> </i> <img src = “image link”.gif/jpg>

<input ...>

<isindex>

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Enclosed text in this font size = Number from 1 to 7 to set text size Encloses a form method = post action = Your e-mail address Start of frame section, which must contain: rows=”*,*,*” Three rows cols=”*,*” Two columns src=url name= name of frame to be used as target for href link scrolling=yes/no/auto Appearance of scroll bars and how they work noresize forces fixed size of frames End frame section Encloses heading information area Sets up text in a heading size, n>1–6 Horizontal rule size = Value in pixels displayed width = Value in pixels or as a percentage noshade This makes the line solid Encloses the whole HTML document Italics Display an image (image source) alt = If image not available then display an alternative piece of text align=top align=bottom align=middle width = Value in pixels or percentages height = Value in pixels or percentages Allows data to be entered name = A variable name which is used to store and reference the data size = Character width type = Checkbox type = Radio type = Reset type = Submit type = Password Contains key words for searches

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APPENDIX: HTML TAGS

<li> <meta>

<noframes> </noframes> <ol> </ol> <p></p>

<pre> </pre> <script></script> <select...>

</select> <span> <sub> </sub> <sup> </sup> <table> </table>

<td ...> </td>

List item Contain useful information about author and keywords, used by search engines for listings Code to be displayed in a browser window which does not support frames Ordered list Start/end a new paragraph align=left align=centre align=right Per-format text; preserves line breaks, font spacing Set-up a Javascript/VBScript work area Sets up a drop-down list name = A variable name which is used to store and reference the data size = The number of items to be displayed at one time multiple Allow for multiple selections value = Return value Ends select Spans an area of code Subscript Superscript Define table area border = Width of border cellspacing = Value in pixels of distance between inner and outer border cellpadding = Value in pixels of distance between text and border Enclose a table data cell colspan= Number of columns to spread cells across rowspan=Number of rows to stretch cells across align=left align=right align=centre align=top valign=middle valign=bottom Vertical alignment width=Value in pixels for width of cell

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APPENDIX: HTML TAGS

<textarea ... >

<th ...> </th> <title> </title> <tr> </tr> <ul> </ul> <var> </var>

164

Multi-line text entry name = a variable name which is used to store and reference the data rows = Number of rows to be displayed cols = Number of columns to be displayed Encloses a table header Defines the name of the document, as it is to appear in the window title bar Encloses a table row An unordered list Variable name

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Higher Information Systems - The Internet  

LT Scotland Higher Information Systems Internet notes

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