Mr C Johnston ICT Teacher G055 - Lecture 04 Wide Area Network Services

Session Objectives Know a range of different services which are available on a Wide Area Network, Explain the purpose of each service and how they work, Explain different methods of connecting a LAN to a WAN and the advantages and disadvantages of each.

Connecting To A WAN There are two main methods of connecting a LAN to a WAN Dialup Modem Connects to traditional analogue telephone lines, Modem changes digital computer data to analogue so can be transferred, Connection is made on demand – dials the number of ISP to connect, Pay monthly or Pay-As-Go pricing models Broadband Permanent always on connection, Uses a router to connect (unless ISDN) – not a modem DSL or Cable or ISDN DSL – Digital Subscriber Line requires a broadband filter (spiltter) so voice and data travel down same line, ADSL – Asymmetric Digital Subscriber Line is most common type of connection – has more space for data transfer to your computer than from your computer to ISP – download speeds good upload speeds slower Cable is far better connection in UK as mostly Fibre – does not deteriorate over distance as much and has very fast speeds (100mb/s about to be launched with a potential speed of 400mb/s) ISDN – Integrated Services Digital Network available to those without a digital telephone exchange but is more expensive and max 2mb but is available to all, Broadband pricing models are a monthly fee for a particular bandwidth, Sometimes have limits on what can download within the price and more is very costly.

Strengths and Weaknesses ConnectionAdvantageDisadvantage Dial-Up Connection is no longer than required Only pay for duration of the call Needs to dial before connected – waiting time Slow data transfer speeds Only suitable for a single machine to be connected Cant use phone and internet at same time unless have multiple lines Broadband Permanent always on internet connection, Much faster connections – Virgin about to roll out 100MB/S, Can use phone and internet on same line, When using DSL service quality depends on distance from exchange, Not all over the country has access to cable / digital exchanges ADSL (Asymmetric Digital Subscriber Lines) have fast download but poor upload speeds Download limits sometimes are imposed to prevent

Services Provided By A WAN Video and Teleconferencing Access to the World Wide Web (www) Access to public domain software Data file exchange (file attachment and FTP) Commercial transactions (e-commerce) Access to newsgroups and discussion boards Web based marketing and advertising Extranets

What Is Public Domain Software Programs that are uncopyrighted because their authors intended to share them with everyone else are in the public domain, Programs in the public domain can be used without restriction as long as you agree to the author’s licence agreement, You are not supposed to make a profit for supplying public domain software.

Benefits and Limitations The software is free, No restrictions, Often has features of expensive software, Software is often reviewed on sites by others who have downloaded it, May have bugs in it, May not have technical support, Might not be exactly what you want, Could be a con – only a demo, a virus, not real thing

Topic Exercise Using the text book create a revision resource which defines each of the services provided by a WAN - Purpose of each, Briefly how each works / kit / technologies involved, Advantages and disadvantages of each, Download and complete this topics exercises. G055 Chapter p13-17 AVCE Unit 08 Chapter p19-21

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