Data Communication

1.1Chapter 1Introduction1.21-1 DATA COMMUNICATIONS1-1 DATA COMMUNICATIONSThe term The term telecommunicationtelecommunication means communication at a means communication at a distance.Theword distance.Theword datadatareferstoinformationpresented referstoinformationpresented inwhateverformisagreeduponbythepartiescreating inwhateverformisagreeduponbythepartiescreating andusingthedata. andusingthedata. DatacommunicationsDatacommunicationsarethe arethe exchangeofdatabetweentwodevicesviasomeformof exchangeofdatabetweentwodevicesviasomeformof transmission medium such as a wire cable. transmission medium such as a wire cable. Components of a data communications system Characteristics of Effective Communication Data FlowTopics discussed in this section:Topics discussed in this section:1.3Figure 1.1Components of a data communication system5 components:1.Message2.Sender 3.Receiver4.Transmission medium5.Protoco1.41. Message : The message is the information(data) to be communicated in form of text, numbers, pictures, audio and video.2. Sender: The sender is the device that sends the data message. It can be a Computer, Workstation, telephone handset, video camera and so on.3. Receiver: The receiver is the device that receives the message. It can be a computer , Workstation, telephone handset, video camera and so on.4. Transmission Medium: The transmission medium is the phsical path b !hich message travels from sender to receiver. "ome examples are t!isted !ire cable, coaxial cable, fiber optic cable and radio !aves.#. $rotocol:% protocol is the set of rules that govern data communication. It represents the agreement bet!een the communication devices. Without a $rotocol, t!o devices ma be connected but not communicating.1.5!ata Communication Mode1."Figure 1.2Data flow (simplex, half-duplex, and full-duplex1.#1-2 NETWORKS1-2 NETWORKS! ! networ"networ" is a set of devices (often referred to as is a set of devices (often referred to as nodesnodes connectedbycommunication connectedbycommunication lin"slin"s.!nodecanbea .!nodecanbea computer, printer, or any other device capable of sending computer, printer, or any other device capable of sending and#orreceivingdatageneratedbyothernodesonthe and#orreceivingdatageneratedbyothernodesonthe networ".! lin"canbeacable,air,opticalfiber,orany networ".! lin"canbeacable,air,opticalfiber,orany mediumwhichcantransportasignalcarrying mediumwhichcantransportasignalcarrying information.information. Network Criteria Physical tructures Categories of NetworksTopics discussed in this section:Topics discussed in this section:1.$Network CriteriaPerformanceDepends on Network Elements!easured in terms of Delay and "hroughput#elia$ilityFailure rate of network components!easured in terms of availa$ility%ro$ustnessecurityData protection against corruption%loss of data due to&Errors!alicious users1.%Physical tructures"ype of ConnectionPoint to Point ' single transmitter and receiver!ultipoint ' multiple recipients of single transmissionPhysical "opologyConnection of devices"ype of transmission ' unicast( mulitcast( $roadcast1.1&Figure 1.)Types of connections: point-to-point and multipoint1.11Figure 1.*Categories of topology1.12Figure 1.+! fully connected mesh topology (five devices1.13Figure 1.,! star topology connecting four stations1.14Figure 1.-! bus topology connecting three stations1.15Figure 1..! ring topology connecting six stations1.1"Figure 1./! hybrid topology: a star bac"bone with three bus networ"s1.1#Categories of Networks0ocal 1rea Networks 201Ns3hort distancesDesigned to provide local interconnectivity4ide 1rea Networks 241Ns30ong distancesProvide connectivity over large areas!etropolitan 1rea Networks 2!1Ns3Provide connectivity over areas such as a city( a campus1.1$Figure 1.15!n isolated $!% connecting &' computers to a hub in a closet1.1%Figure 1.11(!%s: a switched (!% and a point-to-point (!%1.2&Figure 1.12! heterogeneous networ" made of four (!%s and two $!%s1.211-3 THE INTERNET1-3 THE INTERNETThe The )nternet)nternet has revolutioni*ed many aspects of our daily has revolutioni*ed many aspects of our daily lives. )t has affected the way we do business as well as the lives. )t has affected the way we do business as well as the waywespendourleisuretime.The)nternetisa waywespendourleisuretime.The)nternetisa communicationsystemthathasbroughtawealthof communicationsystemthathasbroughtawealthof information to our fingertips and organi*ed it for our use. information to our fingertips and organi*ed it for our use. 6rgani7ation of the 8nternet8nternet ervice Providers 28Ps3Topics discussed in this section:Topics discussed in this section:1.22Figure 1.1)+ierarchical organi*ation of the )nternet1.231-4 PROTOCOLS1-4 PROTOCOLS! protocol is synonymous with rule. )t consists of a set of ! protocol is synonymous with rule. )t consists of a set of rulesthatgoverndatacommunications.)tdetermines rulesthatgoverndatacommunications.)tdetermines what is communicated, how it is communicated and when what is communicated, how it is communicated and when itiscommunicated.The"eyelementsofaprotocolare itiscommunicated.The"eyelementsofaprotocolare syntax, semantics and timingsyntax, semantics and timing ynta9 emantics "imingTopics discussed in this section:Topics discussed in this section:1.24Elements of a Protocolynta9tructure or format of the data8ndicates how to read the $its ' field delineationemantics8nterprets the meaning of the $its:nows which fields define what action"iming4hen data should $e sent and whatpeed at which data should $e sent or speed at which it is $eing received.