CHAPTER 8 TELECOMMUNICATIONS AND NETWORKS 1 TELECOMMUNICATIONS Telecommunications

CHAPTER 8 TELECOMMUNICATIONS AND NETWORKS 1

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 2

Types of Data Text Voice Image Video 3

Basic Communications Model SENDER 4 MEDIUM RECEIVER

COMPONENTS OF A TELECOMMUNICATIONS SYSTEM Computers to process information Terminals or any input/output devices that send or receive data Communications processors Communications software 5

COMPONENTS OF A TELECOMMUNICATIONS SYSTEM Figure 8 -1 6

Basic components of a data communications system Data communications processors PC 7 Data communications Medium PC

FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM Transmit information Establish interface between sender and the receiver Route messages along most efficient paths 8

FUNCTIONS OF A TELECOMMUNICATIONS SYSTEM Perform elementary processing of information Perform editorial tasks on data Convert message speed or format Control flow of information 9

Analog and digital signals Analogue signal: a continuous wave Digital: a discrete set of on (1) and off (0) electronic bursts rather than a continuous wave. 10 +1 0 1 1 0 0

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Communication Media/Channels 4 Guided Media: 4 Twisted Pair 4 Coaxial Cable 4 Optical Fiber 4 Unguided Media: 4 Microwave 4 Satellite 4 Broadcast Radio 12

Guided Media Twisted Pair Coaxial Cable Optical Fiber 13

Unguided Media: Microwave- “Line of sight” media: antennas need to see each other 14

Unguided Media: Satellite 15

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COMMUNICATIONS CHANNELS 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 18

COMMUNICATIONS PROCESSORS AND SOFTWARE 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 19

Computer Networks 4 By geographic span 4 Local Area Network (LAN) 4 Wide Area Network (WAN) 4 By topology (physical) 4 Star 4 Bus 4 Ring 4 Mesh 4 By architecture (logical) 4 Peer to peer versus client-server 4 Centralized versus distributed versus hybrid 20

Network Topology: STAR 21

Network Topology: Bus 22

Network Topology: Ring 23

Network Topology: Mesh Each node is connected to each other node in the network Global Storage Medium 24 Shared Printer

Network Architecture: e. g. , Client-Server • provides global information and software, • manages the use of shared printers, • provides communication within and external to the network. 25

Network Architecture: e. g. , Centralized Network The host computer handles all information processing, manages communication, and stores all software and information. 26

COMMUNICATIONS NETWORKS Private Branch Exchanges Central switching system Handle firm’s voice and digital communications 27

COMMUNICATIONS NETWORKS 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) 28

COMMUNICATIONS NETWORKS A Local Area Network (LAN) 29 Figure 8 -8

COMMUNICATIONS NETWORKS Wide Area Networks (WANs) Span large geographical distance Consist of variety of switched and dedicated lines, satellite, and microwave technologies 30

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COMMUNICATIONS NETWORKS Network Services Value Added Networks: private, multipath, data only, third party managed networks Packet switching technology Frame Relay Asynchronous transfer mode (ATM) 34

Standards and Connectivity for Digital Integration Models of Connectivity for Networks Transmission Control Protocol/Internet Protocol (TCP/IP) Open Systems Interconnect (OSI) 35

Standards and Connectivity for Digital Integration (TCP/IP) Reference Model Figure 9 -2 36

PC to PC Communication using TCP/IP PC-1 PC-2 Application protocol HTTP Request TCP HTTP Request Transport protocol TCP HTTP Request IP protocol IP IP TCP HTTP Request Data Link protocol Data Link Ethernet IP TCP HTTP Request Ethernet Physical layer Physical medium: e. g. , Ethernet cable 37

COMMUNICATIONS NETWORKS Packed-Switched Networks and Packet Communications 38 Figure 8 -9

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 D A Switch B 39 E Trunk Line C

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 D Trunk Line A Switch B 40 Switch E C

ELECTRONIC DATA INTERCHANGE EDI Direct computer to computer exchange between two organizations of standard business transaction documents Lower transaction cost Provide strategic benefits by increasing switching cost 41