COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School INTRODUCTION TO NETWORKING LESSON 8

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School LESSON OVERVIEW  COMMUNICATION CHANNELS BETWEEN COMPUTERS  DEFINITION OF COMPUTER NETWORKS  TYPES OF NETWORKS  NETWORK CONFIGURATION TYPES

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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.

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School TRANSMISSION METHODS  Telephone Lines  Satellite Links  Microwave Relay

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School TYPES OF CABLE  Twisted wire (phone line)  Coaxial Cable (Round Insulated Wire)  Fibre Optic Line (Glass Fibre)

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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 Wi-Fi AdvantagesDisadvantages  Speed of light  Uses a few sites  Line of sight only

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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) transponders / satellite at 50Mbs/transponder AdvantagesDisadvantages  Always in sight  They can be used to send large volumes of data  Expensive uplink and downloading facilities

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School Wireless AdvantagesDisadvantages  Flexible  Portable  Slower  Subject to interference

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School COMPUTER NETWORKS More complexity adds new problems to handle. 2 of 3 DISADVANTAGESDISADVANTAGES

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School A SIMPLE NETWORK

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School TYPES OF NETWORKS  Local Area Networks or LANs  Metropolitan Area Network or MAN  Wide Area Network or WAN

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School LOCAL AREA NETWORKS, LANS

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School METROPOLITAN AREA NETWORK, MAN

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School WIDE AREA NETWORK, WAN

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School NETWORK CONFIGURATION TYPES  Star  Bus  Ring

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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

COMPUTER SYSTEM FUNDAMENTAL Genetic Computer School 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