Local & Wide Area Networks

Networks A network is two or more computers linked together Networks are used to share programs, data and resources. There are two main types of network LAN (Local Area Network) WAN (Wide Area Network) Computers on a network are called stations. One station on the network is a powerful computer called a file server.

Local Area Network (LAN) covers a small area such as a room, building and is usually owned by an individual, company or small organisation Is a fast network Is connected by its own wiring

Advantages of LAN’s Share data and programs between stations Share resources, e.g. peripherals such as printers, scanners. Sharing makes it cheaper Use e-mail service

Advantages of LAN’s Keep data secure using passwords Reduce unauthorised access using different level of access (read-only) Allow users to access their files from any computer on the network Allow users to work on the same files at the same time (multi access)

LAN Transmission Media copper wire fibre optic (glass) infrared bluetooth WiFi

WAN (Wide Area Networks) A network that covers a large geographical area such as a country or the whole world!! The Internet is one example

Advantages of WAN’s Same as LAN’s except you do not usually share peripherals Send e-mail worldwide Video conferencing Voice over data (Free phone calls worldwide)

WAN Transmission Media Any communication carried over a long distance is called telecommunication. A WAN uses the telephone system which includes: Copper cables Microwave transmission links Satellite links Optical fibres links

Network Security Data can be lost through accidents system failures deliberate action (unauthorised access) There are two ways of securing data: physical security electronic security

Physical Security locks on rooms identity cards (Magnetic stripe or Smart card) biometrics - fingerprint, iris scan or voice print stand-alone computer

Electronic Security Passwords Levels of access Encryption (putting into code) Very important in wireless networks

Absolute Security "Three may keep a secret if two of them are dead" Ben Franklin NO NETWORK!!

Client & Server Network A computer that delivers data and software to other computers (clients) linked by a network. Usually has Fast processor Large memory Large hard disc Two-tier Client/Server In two-tier client/server, the database processing is done in the server. A SQL request is generated in the client and transmitted to the server. The DBMS searches for records at the server side and returns only matching records to the client. If 50 records met the criteria in our 100,000-record example, only 50KB would be transmitted over the LAN. Three-tier Client/Server In three-tier client/server, the processing is divided between two or more servers, one typically used for application processing and another for database processing. This is common in large enterprises. Because of the Internet, terms such as "Web based" and "Web enabled" have replaced the client/server buzzword, yet the client/server architecture is conceptually the same. Users' desktop and laptop computers are still clients, and there are hundreds of thousands of Web servers throughout the Internet delivering Web pages. Nevertheless, client/server is mostly used to refer to "legacy," non-Web based systems. What makes the term even fuzzier is the fact that many "old" client/server systems have been modified to include Web access. On the Web, the client runs the browser and just like legacy client/server can perform little or a lot of processing: simple displaying of HTML pages, more processing with embedded scripts or considerable processing with Java applets. A myriad of browser plug-ins provide all sorts of client-side processing. The server side of the Web is a multi-tier server architecture with interlinked Web servers, application servers, database servers and caching servers. See application server.

Types of servers File Mail CD Internet CD-Server A CD-ROM reader designed for network use. It can be configured as a tower or jukebox. Towers contain several drives, and each drive holds one CD-ROM. Jukeboxes hold from a couple dozen to hundreds of discs, but have only a small number of drives. A robotic mechanism moves the discs to the drives as required.

File Server A file server stores programs data list of all users allowed access to the network (authorised users) Once you have logged-on the file server allows you access to the network (on-line) Logging–on: identifies a user to the file server ( usually by entering username & password) File server A high-speed computer in a network that stores the programs and data files shared by users. It acts like a remote disk drive. The difference between a file server and an application server is that the file server stores the programs and data, while the application server runs the programs and processes the data.

Network Interface Card (NIC) This is a small circuit board that allows the computer to communicate with a computer network. Some computers have a wireless network interface card that allows them to communicate with a nearby LAN

Social, Legal & Ethical Issues

Social Issues

Teleworking This is the process of working from home and using a computer to connect to a wide area network to communicate with the office. There are several advantages to employees and employers:

Advantages of Teleworking Advantages to employees: Choose own working hours Save money on fuel, child care costs Reduce congestion on the roads, pollution and travelling time Advantages to employers: Do not have to provide premises, heating lighting, rent, rates.

Disadvantages of Teleworking Disadvantages to Employees: May not be given same rights to health & safety (electrical faults) Workers may become isolated or lonely Disadvantages to Employers Must ensure all electrical equipment complies with health & safety issues Must take responsibility for ‘information security’ of remote workers

Social Benefits of WAN Advantages: Improve communication in isolated areas & reduce isolation Allow people to keep in contact with family abroad via e-mail & websites People connected to the Internet have access to a large pool of information (Information rich) Disadvantages: May increase social isolation as more people go on-line (become detached from real world) Costly – those not connected may be further disadvantages (Information poor)

Legal Issues

Legal Issues Laws which affect computers include: Computer Misuse Act The Data Protection Act The Copyright, Designs & Patents Act The Privacy and Electronic Communications Regulations 2003

Computer Misuse Act Unauthorised access (hacking) Creating a virus A progam that copies itself that may cause harm

The Data Protection Act (1998) This Act compels any company to take specific measures to ensure that all personal information held about living (identified or identifiable) individuals is processed according to eight Data Protection Principles

Data Protection Act Principles Data users must Obtain and process the data fairly and lawfully Register the purpose for which they hold it Use only for this purpose Hold only adequate and relevant data Keep data accurate and up-to-date Not keep data longer than necessary Give individuals access to their own data Take appropriate security measures

Data Protection Act Exemptions Law Enforcement National Security Examination Marks and Examiners’ Comments Adoption Records and Reports Lawyer-client communications.

The Copyright, Designs and Patents Act (1988) “intellectual property” “expression of an idea” all computer software, whether covered by a specific licence or not, is copyrighted under this Act. the program itself screen shots associated documentation

Privacy and Electronic Communications Regulations 2003 This act makes it illegal for companies to send you unsolicited e-mail (Junk Mail). Note: Unsolicited means something that you did not ask for. Companies must get permission from an individual before they can send them an e-mail or text An Individual must be given the choice of refusal Unsolicited means something that you did not ask for. Note: this does not mean it is unwanted 1 NEW RULES ON EMAIL MARKETING WHAT DO THEY MEAN FOR INDIVIDUALS? From 11 December 2003, two new rules will apply to email marketing when the Privacy and Electronic Communications (EC Directive) Regulations 2003 come into force. 1st New Rule This rule applies to all marketing messages sent by electronic mail, regardless of who the recipient is. • The sender must not conceal their identity and • The sender must provide a valid address for opt-out requests 2nd New Rule This rule only applies to unsolicited marketing messages sent by electronic mail to individual subscribers. • Senders cannot send such messages unless they have the recipient’s prior consent to do so. This strict “opt-in” rule is relaxed if three exemption criteria are satisfied. These three exemption criteria are as follows 1. The recipient’s email address was collected “in the course of a sale or negotiations for a sale” 2. The sender only sends promotional messages relating to their “similar products and services” AND 3. When the address was collected, the recipient was given the opportunity to opt out (free of charge except for the cost of transmission) which they didn’t take. The opportunity to optout must be given with every subsequent message. GLOSSARY OF TERMS “Electronic mail” This means email and text/picture/video messages “Individual subscriber” This means a residential subscriber, a sole trader or an unincorporated partnership in England, Wales and N. Ireland. “unsolicited” This means something that is not invited. However, it does not mean something that is “unwanted”. For example, you might welcome information about special promotions from a company that you trust and who always offers a good deal. You have not specifically “invited” these offers but you have told the company that you don’t mind receiving information about special promotions that they choose to send you. You may or may not take up the offer if it interests you.

Ethical Issues

Ethical Issues These are concerned with people’s judgement as to what is right or wrong. Invasion of personal privacy Is it acceptable for government bodies [NSA(US), GCHQ(UK)] to intercept private data sent across networks to prevent terrorism & crime Censorship & freedom of speech Should anyone be able to set up a website even though it is used to incite hatred & racism Should the government be able to block these web sites, e.g. bomb making

Local & Wide Area Networks End of presentation