Data communications

Chapter 1IntroductionUnderstand the difference between telecommunications anddata communications.List the components of a data communications system.Understand the need for a network and distinguish betweendifferent network types.Understand the difference between a protocol and a standard.After reading this chapter, the reader should be able to:OBJECTIVESOBJECTIVES (continued)Understand the duties of the layers in the OSI model.Understand the duties of the layers in the Internet model.Be able to compare the layers in the OSI and Internet model. Be familiar with standards organizations and their duties.DATACOMMUNICATIONS1.1In computer information systems, data are represented by binary information units (or bits) produced and consumed in the form of 0s and 1s.Note:Figure 1-1Data communications system components In data communications, a protocol is a set of rules (conventions) that governs all aspects of information communication.Note:NETWORKS1.2Figure 1-2Network criteriaFigure 1-3LANFigure 1-4MANFigure 1-5WANFigure 1-6Internetwork (internet)Technical Focus: Representing InformationInformation stored inside the computer consists of only two symbols: 0 and 1. This is because the memory of the computer is made of electronic switches that are either on or off. When the switch is off, it stores a 0; when the switch is on, it stores a 1. This means that any type of information must be represented as a sequence of 0s and 1s for storage inside the computer. Because data communications is the process of moving information from one computer to another, data communications also uses 0s and 1s to represent information. PROTOCOLSANDSTANDARDS1.3Figure 1-7Categories of standardsSTANDARDSORGANIZATIONS1.4Business Focus: Standards OrganizationsThe following are some standards organizations:ISOANSIITU-TIEEEEIABusiness Focus: FCCSpecific FCC responsibilities include the following:Review rate and service-charge applicationsEstablish reasonable ratesReview technical specificationsDivide and allocate radio frequenciesAssign carrier frequencies for radio and televisionNETWORKMODELS1.5Figure 1-8OSI modelFigure 1-9Application layerFigure 1-10Presentation layerFigure 1-11Session layerFigure 1-12Transport layerFigure 1-13Network layerFigure 1-14Data link layerFigure 1-15Physical layerFigure 1-16Summary of layer functionsFigure 1-17The Internet model