Networks
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LOCAL AREA NETWORKS ( LAN )
Computers are connected together on one site using a cable such as ethernet
The File server stores all programs and data.
Relative Advantages of a LAN compared to stand alone computers
- Can share expensive peripherals ( e.g. laser printer / CD-ROM )
- Easy to share information
- Electronic mail - Send messages
Problems with LAN
- If the File Server fails or there is a cable problem then the whole system may fail.
- Security and privacy of information stored on the file server may be in danger.
DATA SECURITY AND PRIVACY ON A NETWORK
Security is the protection of data from accidental or malicious loss.
Privacy is making sure people don't read confidential information.
Protecting the data
- Individual log one have passwords
- Have different levels of access
e.g. - in a school
- teachers have full access
- pupils have restricted access
- in a hospital
- Doctors can change data
- nurses can't - they can only view it
- File access - make 'Read Only' - so people can't change
- Regular tape backups
WIDE AREA NETWORKS ( WAN )
Computers are linked from one site to another using the telephone network.
Equipment needed
- Modem - to transfer the computers digital signals into an analogue form for the telephone system.
Modems will be made obsolete by the introduction of digital phone links - ISDN
- Multiplexor - A device which acts a temporary store ( buffer ) when
many incoming computer calls are being received at the same time.
USES OF WAN
Electronic mail
The mailbox is held on a central computer. You receive your messages when you log-on.
Could be used by travelling sales reps. Companies leave messages for people in different countries / time zones.
EDF - Electronic data Interchange
Your exam entries and results will be transferred to & from the exam boards.
Banks move money by EFF- Electronic Funds Transfer.
Commercial Booking / Reservation Systems
Travel Agents use a WAN to book holidays / aeroplane seats. This system must be on-line
and work in real time to prevent duplicate bookings.
Databases
Commercial systems such as Viewdata ( Prestel ) allow you to access
information on companies, share prices etc.
THE INTERNET
This has given individuals access to a global WAN.
Set-up & Costs requirements.
- Modem or ISDN link
- Sign up & pay an Internet provider e.g. AOL or Compuserve, who will give you an internet address.
- Telephone costs - local rate anywhere in the world.
Uses of the Internet for individuals.
- User Groups - e.g. Astronomers, Disabled.
- Information databases e.g. Newspapers.
- Research / education - Global searches using a web browser - sometimes called ' Surfing '
- Electronic mail - sending messages.
- Chat groups.
- Your own web pages . You can advertise your business.
You will need a hypertext editor to do this.
Internet log-on process requires you to enter your user ID and
password to stop others using your service.
WAN ISSUES
Data Security
Private Data must be encrypted ( coded ) to prevent hackers from downloading information.
Network Protocols ( Standards )
So that all global data can be linked. OSI standards and gateways exist.
Other Communication Topics
- Fax / Facsimile Machines
- Teletext - computerised data storage & transmission
- Remote data logging.
Typical Exam Questions
- Advantages / disadvantages of networks
- Advantages of using electronic mail compared with more traditional
methods - e.g. You can guarantee message has been received
- Security / privacy Issues
- The future of data communication e.g. Teleconferencing
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by: Admin
Total views: 1469
Word Count: 999
Date: Wed, 2 Aug 2006 Time: 12:00 AM
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