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1 CHAPTER 8 TELECOMMUNICATIONSANDNETWORKS
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2 TELECOMMUNICATIONS Telecommunications: Communication of all types of information, including digital data, voice, fax, sound, and video from one location to another over some type of network Network: A group of computers and associated peripheral devices connected by a communication channel of sharing information and other resources among users
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3 Text Voice Image Video Types of Data
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4 SENDER RECEIVER MEDIUM Basic Communications Model
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5 COMPONENTS OF A TELECOMMUNICATIONS SYSTEM Computers to process information Terminals or any input/output devices that send or receive data Communications processors Communications software
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6 Figure 8-1 COMPONENTS OF A TELECOMMUNICATIONS SYSTEM
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7 PC Data communications processors PC Basic components of a data communications system Data communications Medium
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8 Transmit information Establish interface between sender and the receiver Route messages along most efficient paths FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM
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9 Perform elementary processing of information Perform editorial tasks on data Convert message speed or format Control flow of information FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM
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10 Analogue signal: a continuous wave Digital: a discrete set of on (1) and off (0) electronic bursts rather than a continuous wave. +1 0 0 11 0 Analog and digital signals
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12 Communication Media/Channels Guided Media: Twisted Pair Coaxial Cable Optical Fiber Unguided Media: Microwave Satellite Broadcast Radio
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13 Twisted Pair Coaxial Cable Optical Fiber Guided Media
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14 Microwave- “Line of sight” media: antennas need to see each other Unguided Media: Microwave
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15 Unguided Media: Satellite
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18 Transmission Speed Total amount of info that can be transmitted through any channel is measured in bits per second Baud: change in signal from + to – or vice versa that is used as a measure of transmission speed Frequency: the number of cycles per second that can be sent through that medium (in hertz) Bandwidth: the range of frequencies that can be accommodated on a particular communication channel COMMUNICATIONS CHANNELS
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19 Front-end processor: Manages communications for the host computer Concentrator: Collects and temporarily stores messages Controller: Supervises communication traffic between CPU and peripheral devices Multiplexer: Enables single communication channel to carry data transmissions from multiple sources simultaneously COMMUNICATIONS PROCESSORS AND SOFTWARE
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20 By geographic span Local Area Network (LAN) Wide Area Network (WAN) By topology (physical) Star Bus Ring Mesh By architecture (logical) Peer to peer versus client-server Centralized versus distributed versus hybrid Computer Networks
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21 Network Topology: STAR
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22 Network Topology: Bus
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23 Network Topology: Ring
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24 Each node is connected to each other node in the network Global Storage Medium Shared Printer Network Topology: Mesh
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25 Network Architecture: e.g., Client-Server Server provides global information and software, manages the use of shared printers, provides communication within and external to the network.
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26 The host computer handles all information processing, manages communication, and stores all software and information. Network Architecture: e.g., Centralized Network
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27 Private Branch Exchanges Central switching system Handle firm’s voice and digital communications COMMUNICATIONS NETWORKS
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28 Local Area Networks Encompass a limited distance Require its own communication channels Support high volumes of data and functions requiring high transmission speed Gateway, router, Network Operating System (NOS) COMMUNICATIONS NETWORKS
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29 A Local Area Network (LAN) Figure 8-8 COMMUNICATIONS NETWORKS
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30 Wide Area Networks (WANs) Span large geographical distance Consist of variety of switched and dedicated lines, satellite, and microwave technologies COMMUNICATIONS NETWORKS
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34 Network Services Value Added Networks: private, multipath, data only, third party managed networks Packet switching technology Frame Relay Asynchronous transfer mode (ATM) COMMUNICATIONS NETWORKS
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35 Models of Connectivity for Networks Transmission Control Protocol/Internet Protocol (TCP/IP) Open Systems Interconnect (OSI) Standards and Connectivity for Digital Integration
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36 (TCP/IP) Reference Model Figure 9-2 Standards and Connectivity for Digital Integration
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37 Application TCP IP Data Link Physical layer Application protocol Transport protocol IP protocol Data Link protocol Physical medium: e.g., Ethernet cable PC-1 PC-2 PC to PC Communication using TCP/IP RequestHTTP TCP RequestHTTP IPTCP RequestHTTP Ethernet IPTCP RequestHTTP RequestHTTP TCP RequestHTTP IPTCP RequestHTTP Ethernet IPTCP RequestHTTP
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38 Packed-Switched Networks and Packet Communications Figure 8-9 COMMUNICATIONS NETWORKS
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39 Packet Switching Packet switching breaks transmissions into packets When a packet arrives at a switch, the switch must decide where to send the packet next Switch A B C D E Trunk Line
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40 Circuit Switching End-to-end connection between phones May pass through multiple switches and trunk lines Reserved (guaranteed) capacity during call Reserved circuit capacity is expensive Good for voice/bad for data Capacity is wasted between bursts, but still must pay for capacity Switch Trunk Line Switch A BC D E
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41 EDI Direct computer to computer exchange between two organizations of standard business transaction documents Lower transaction cost Provide strategic benefits by increasing switching cost ELECTRONIC DATA INTERCHANGE
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