1. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-1 INTRODUCTION TO NETWORKING LESSON 8

2. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-2 LESSON OVERVIEW  COMMUNICATION CHANNELS BETWEEN COMPUTERS  DEFINITION OF COMPUTER NETWORKS  TYPES OF NETWORKS  NETWORK CONFIGURATION TYPES

3. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-3 COMMUNICATION CHANNELS BETWEEN COMPUTERS  Data Communications for transmission of data and information over a communications channel  Telecommunications for any long-distance communications, especially television  Teleprocessing for accessing computer files located elsewhere A communications channel, also called a communications line or link, is the path that the data follows as it is transmitted from one computer to another.

4. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-4 TRANSMISSION METHODS  Telephone Lines  Satellite Links  Microwave Relay

5. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-5 TYPES OF CABLE  Twisted wire (phone line)  Coaxial Cable (Round Insulated Wire)  Fibre Optic Line (Glass Fibre)

6. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-6 COAXIAL CABLE  Wire surrounded by insulation  Copper shield around insulation Acts as signal return Shields from external noise  High bandwidth: 100 Mbps Example: analog cable TV with FDM for dozens of channels at 6 MHz

7. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-7 TWISTED PAIR  Some networks and phone lines in buildings  More susceptible to noise than coaxial cable  Used for shorter distances and slower signals

8. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-8 FIBER OPTIC CABLE  Consists of glass fiber thinner than human hair  Uses light to carry signals  Laser or light-emitting diode produces signal  Cladding: plastic sheath to protect fibers

9. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-9 Twisted wire (phone line) Coaxial Cable (Round Insulated Wire) Fibre Optic Line (Glass Fibre)  Easy to string  Cheap  Not susceptible to interference  Transmits faster  Smaller, lighter, faster (speed of light)  No interference, therefore more secure  Subject to interference – static and garble  Heavy and bulky  Expensive  Harder to install and modify  Limited in the distance they can carry information. ADVANTAGESADVANTAGES DISADVANTAGESDISADVANTAGES CABLES

10. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-10 MICROWAVE  Frequencies below light  Unguided medium  Tightly focused for point-to-point use  Highly susceptible to interference  Applications  Large-scale Internet backbone channels  Direct satellite-to-home TV  IEEE 802.11 Wi-Fi AdvantagesDisadvantages  Speed of light  Uses a few sites  Line of sight only

11. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-11 SATELLITE (INFRARED LIGHT, RADIO) Satellite is a relay station Early systems with geostatonary satellite (at 35,784km). Satellite receives on one frequency (uplink), amplifies or repeats signal and transmits on another frequency (downlink). 15-20 transponders / satellite at 50Mbs/transponder AdvantagesDisadvantages  Always in sight  They can be used to send large volumes of data  Expensive uplink and downloading facilities

12. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-12 Wireless AdvantagesDisadvantages  Flexible  Portable  Slower  Subject to interference

13. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-13 DEFINITION OF COMPUTER NETWORKS A network is a set of computers, which are linked together on a permanent basis.  Two Computers Cabled Together On The Same Desk  Thousands Of Computers Across The World

14. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-14 COMPUTER NETWORKS Enables users to share hardware like scanners and printers. This reduces costs by reducing the number of hardware items bought. ADVANTAGESADVANTAGES 1 of 3

15. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-15 COMPUTER NETWORKS Allows users access to data stored on others' computers. This keeps everyone up-to-date on the latest data, since it's all in the same file, rather than having to make copies of the files, which are immediately out- of-date. ADVANTAGESADVANTAGES 2 of 3

16. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-16 COMPUTER NETWORKS Can even let users run programs that are not installed on their own computers but are installed elsewhere in the network. This reduces the effort for networks administrators to keep programs configured correctly and saves a lot of storage space. ADVANTAGESADVANTAGES 3 of 3

17. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-17 COMPUTER NETWORKS Accessing anything across a network is slower than accessing your own computer. 1 of 3 DISADVANTAGESDISADVANTAGES

18. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-18 COMPUTER NETWORKS More complexity adds new problems to handle. 2 of 3 DISADVANTAGESDISADVANTAGES

19. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-19 COMPUTER NETWORKS Less customization is possible for shared programs and folders. Everyone will have to follow the same conventions for storing and naming files so others can find the right files. DISADVANTAGESDISADVANTAGES 3 of 3

20. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-20 THINGS NEEDED FOR A NETWORK  Protocol A set of communication rules to make sure that everyone speaks the same language  Network interface cards (NICs) Cards that plugs into the back (or side) of your computers and lets them send and receive messages from other computers  Cable The medium to connect all of the computers together  Hub Hardware to perform traffic control

21. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-21 A SIMPLE NETWORK

22. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-22 TYPES OF NETWORKS  Local Area Networks or LANs  Metropolitan Area Network or MAN  Wide Area Network or WAN

23. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-23 LOCAL AREA NETWORKS, LANS

24. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-24 METROPOLITAN AREA NETWORK, MAN

25. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-25 WIDE AREA NETWORK, WAN

26. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-26 NETWORK CONFIGURATION TYPES  Star  Bus  Ring

27. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-27 StarBusRing  Gives close control of data.  Each PC sees all the data.  User sees up-to-date data always.  If a computer other than the host fails, no other computer is affected.  Any one computer or device being down does not affect the others.  It is also easy to add PCs to the Net.  It is less expensive and is in very common use.  Requires less cabling and so is less expensive. ADVANTAGES

28. COMPUTER SYSTEM FUNDAMENTAL Copyright @ Genetic Computer School 2008 8-28 StarBusRing  If host computer or its software goes down, the whole network is down. (A backup computer system would be necessary to keep going while repairs are made.)  It is also hard to extend to the Internet also.  Cannot connect a large number of computers in this way.  It's physically difficult is to run the one communications line over a whole building.  If one node goes down, it takes down the whole network. DISADVANTAGES