Chapter 1 - William Stallings, Data And Computer .

Transcription

Data and ComputerCommunicationsChapter 1 – Data Communications,Data Networks, and the Internet

Data Communications, DataNetworks, and the Internet“The fundamental problem ofcommunication is that of reproducing atone point either exactly or approximately amessage selected at another point”- The Mathematical Theory of Communication,Claude ShannonMessageMessage

Technological AdvancementDriving ForcesTrafficgrowth ata high &steadyrate Development ofnew services Advances intechnology

Changes in NetworkingTechnology* Emergence of high-speed LANs* Corporate WAN needs* Digital electronics

Convergence Themerger of previously distinct telephonyand information technologies and markets Layers: applications these are seen by the end users enterprise services services the information network supplies to supportapplications infrastructure communication links available to the enterprise

Convergence Layers

BenefitsConvergence benefits include:EfficiencyEffectivenessTransformation better use ofexistingresources, andimplementationof centralizedcapacityplanning, assetand policymanagement the convergedenvironmentprovides userswith flexibility,rapidstandardizedservicedeployment andenhancedremoteconnectivityand mobility enables theenterprise-wideadoption ofglobalstandards andassociatedservice levels

Communications Model

Communications TasksTransmission system utilization AddressingInterfacingRoutingSignal generationRecoverySynchronizationMessage formattingExchange managementSecurityError detection and correctionNetwork managementFlow control

Data Communications Model

Transmission LinesCapacityThe basic building block ofany communications facilityis the transmission line.The business manager isconcerned with a facilityproviding therequired capacity,with acceptable reliability,at minimum cost.ReliabilityCostTransmissionLine

Two mediums currently drivingthe evolution of data communicationstransmission are:and

NetworkingAdvances in technology have led to greatlyincreased capacity and the concept ofintegration, allowing equipment andnetworks to work simultaneously.VoiceDataImageVideo

LANs and WANsThere are two broad categoriesof networks:Local Area Networks (LAN)Wide Area Networks (WAN)

Wide Area Networks (WANs) Spana large geographical area Require Relythe crossing of public right-of-waysin part on common carrier circuits Typicallyconsist of a number ofinterconnected switching nodes

Wide Area NetworksAlternative technologies used include: Circuit switchingPacket switchingFrame relayAsynchronous Transfer Mode (ATM)

Circuit Switching Usesa dedicated communications path Connected sequence of physical linksbetween nodes Logical channel dedicated on each link Rapid transmission The most common example of circuitswitching is the telephone network

Packet Switching Dataare sent out in a sequence of smallchunks called packets Packets are passed from node to nodealong a path leading from source todestination Packet-switching networks are commonlyused for terminal-to-terminal computer andcomputer-to-computer communications

Frame Relay Developedto take advantage of high datarates and low error rates Operates at data rates of up to 2 Mbps Rate of errors dramatically lowered thusreducing overhead of packet-switching

Asynchronous Transfer Mode(ATM) Referredto as cell relay Culmination of circuit switching and packetswitching Uses fixed-length packets called cells Works in range of 10’s and 100’s of Mbpsand in the Gbps range Data rate on each channel dynamically seton demand

Local Area Networks (LAN)

Metropolitan Area Networks(MAN)

The Internet Internetevolved from ARPANET Developed to solve the dilemma ofcommunicating across arbitrary, multiple,packet-switched network TCP/IP provides the foundation

Internet Key Elements

Internet Architecture

InternetTerminology

A Networking Configuration

Summary Trendschallenging data communications: traffic growth development of new services advances in technology Transmissionmediums fiber optic wireless Networkcategories: WAN LAN Internet evolved from the ARPANET TCP/IP foundation

Data and Computer Communications Chapter 1 – Data Communications, Data Networks, and the Internet . Data Communications, Data Networks, and the Internet “The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point” - The Mathematical Theory of Communication, Claude Shannon Message Message .