Principles of Information Systems Seventh Edition Effective communications

Principles of Information Systems, Seventh Edition

• Effective communications are essential to organizational success • Define the terms communications and telecommunications and describe the components of a telecommunications system Principles of Information Systems, Seventh Edition 2

• An unmistakable trend of communications technology is that more people are able to send and receive all forms of information over greater distances at a faster rate • Identify broad categories of communications media and discuss the basic characteristics of specific media types • Describe how a modem works • Explain the types of telecommunications carriers today and the services they provide Principles of Information Systems, Seventh Edition 3

• Identify the benefits associated with a telecommunications network • Define the term network topology and identify five alternatives • Discuss the different communications protocols and devices used for telecommunications • Name three distributed processing alternatives and discuss their basic features • List some telecommunications applications that organizations are benefiting from today Principles of Information Systems, Seventh Edition 4

An Overview Of Communications Systems • Communications: the transmission of a signal by way of a medium from a sender to a receiver • Signal contains a message composed of data and information • In telecommunications, sender transmits a signal through a transmission medium such as a cable Principles of Information Systems, Seventh Edition 5

Figure 6. 2: Communications and Telecommunications Principles of Information Systems, Seventh Edition 6

An Overview Of Communications Systems (continued) • Communications can be synchronous or asynchronous • Synchronous communications: the receiver gets the message instantaneously • Asynchronous communications: the receiver gets the message some period of time after it is sent Principles of Information Systems, Seventh Edition 7

Telecommunications • Telecommunications: electronic transmission of signals for communications, via telephone, radio, television, etc. • Data communications: subset of telecommunications that refers to the electronic collection, processing, and distribution of data, typically between computer system hardware devices • Telecommunications medium: anything that carries an electronic signal and interfaces between a sending device and a receiving device Principles of Information Systems, Seventh Edition 8

Figure 6. 3: Elements of a Telecommunications System Principles of Information Systems, Seventh Edition 9

Communications Channels: Basic Communications Channel Characteristics • Communication channels can be classified as simplex, half-duplex, or full-duplex • Simplex channel: can transmit data in only one direction • Half-duplex channel: can transmit data in either direction, but not simultaneously • Full-duplex channel: permits data transmission in both directions at the same time Principles of Information Systems, Seventh Edition 10

Channel Bandwidth and Information. Carrying Capacity • Bandwidth: the range of frequencies that an electronic signal occupies on a given transmission medium • Shannon’s fundamental law of information theory: states that the information-carrying capacity of a channel is directly proportional to its bandwidth • Broadband: telecommunications in which a wide band of frequencies is available to transmit information Principles of Information Systems, Seventh Edition 11

Types of Media • Guided transmission media: communications signals are guided along a solid medium • Wireless media: communications signals are sent over airwaves Principles of Information Systems, Seventh Edition 12

Table 6. 1: Transmission Media Types Principles of Information Systems, Seventh Edition 13

Table 6. 1: Transmission Media Types (continued) Principles of Information Systems, Seventh Edition 14

Modems • A typical telephone line can only accommodate an analog signal (a continuous, curving signal) • A computer generates a digital signal representing bits • Modem: a device that translates data from digital to analog and analog to digital Principles of Information Systems, Seventh Edition 15

Figure 6. 8: How a Modem Works Principles of Information Systems, Seventh Edition 16

Multiplexers • Multiplexers: devices that allow several telecommunications signals to be transmitted over a single communications medium at the same time Principles of Information Systems, Seventh Edition 17

Figure 6. 9: Use of a Multiplexer to Consolidate Data Communications onto a Single Communications Link Principles of Information Systems, Seventh Edition 18

Front-End Processors • Front-end processors: special-purpose computers that manage communications to and from a computer system • Connect a midrange or mainframe computer to hundreds or thousands of communications lines Principles of Information Systems, Seventh Edition 19

Figure 6. 10: Front-End Processor Principles of Information Systems, Seventh Edition 20

Carriers and Services • Local exchange carrier (LEC): a public telephone company in the United States that provides service to homes and businesses within its defined geographical area • Competitive local exchange carrier (CLEC): a company that is allowed to compete with the LECs, such as a wireless, satellite, or cable service provider • Long-distance carrier: a traditional long-distance phone provider, such as AT&T, Sprint, or MCI Principles of Information Systems, Seventh Edition 21

Switched and Dedicated Lines • Switched line: a communications line that uses switching equipment to allow one transmission device to be connected to other transmission devices • Dedicated line: a communications line that provides a constant connection between two points; also called a leased line Principles of Information Systems, Seventh Edition 22

Voice and Data Convergence • Voice over Internet protocol (Vo. IP): the basic transport of voice in the form of a data packet using the Internet protocol • IP telephony is the technology for transmitting voice communications over a network using an open standardsbased Internet protocol • Voice and data convergence: the integration of voice and data applications in a common environment Principles of Information Systems, Seventh Edition 23

WATS • Wide-area telephone service (WATS): a fixed-rate long -distance telecommunications service for heavy users of voice services • IN-WATS service • OUT-WATS service Principles of Information Systems, Seventh Edition 24

ISDN • Integrated services digital network (ISDN): a set of standards for integrating voice and data communications onto a single line via digital transmission over copper wire or other media • ISDN requires special adapters at both ends of the transmission line • ISDN Basic Rate Interface • ISDN Primary Rate Interface Principles of Information Systems, Seventh Edition 25

Figure 6. 12: ISDN Network Switching Principles of Information Systems, Seventh Edition 26

T-Carrier System • Introduced in the 1960 s to support digitized voice transmission • Uses four wires and provides duplex capability • T-1 carrier is capable of carrying 1. 544 Mbps over copper wire; commonly used in U. S. , Japan, and Canada • T-3 line is capable of transmitting data at a rate of 44. 736 Mbps Principles of Information Systems, Seventh Edition 27

Digital Subscriber Line (DSL) • Digital subscriber line (DSL): a telecommunications technology that delivers high-bandwidth information to homes and small businesses over ordinary copper telephone wires • Provides a transmission rate of 512 Kbps to 1. 544 Mbps from the central office to the subscriber • Provides a transmission rate of about 128 Kbps from the subscriber to the central office • Can carry both data and voice signals Principles of Information Systems, Seventh Edition 28

Wireless Mobile Table 6. 3: Some Wireless Data Communications Options Principles of Information Systems, Seventh Edition 29

Networks • Computer network: the communications media, devices, and software needed to connect two or more computer systems and/or devices • Network nodes: the computers and devices on the networks Principles of Information Systems, Seventh Edition 30

Network Types • Personal area network (PAN) • Local area network (LAN) • Metropolitan area network (MAN) • Wide area network (WAN) • International network Principles of Information Systems, Seventh Edition 31

Network Topology • Network topology: logical model that describes how networks are structured or configured Principles of Information Systems, Seventh Edition 32

Figure 6. 15: The Basic Network Topologies Principles of Information Systems, Seventh Edition 33

Terminal-to-Host, File Server, and Client/Server Systems • Classifications based on how computers on the network connect and interoperate • Terminal-to-host: application and database reside on one host computer, and the user interacts with application and data using a “dumb” terminal • File server: the application and database reside on one host computer (file server) • Client/server: multiple computer platforms are dedicated to special functions such as database management, printing, communications, and program execution Principles of Information Systems, Seventh Edition 34

Figure 6. 18: Client/Server Connection Principles of Information Systems, Seventh Edition 35

Interconnecting Networks: Communications Protocols • Open Systems Interconnection (OSI) model • Transmission Control Protocol/Internet Protocol (TCP/IP) • Systems Network Architecture (SNA) • IEEE 802. 3 (Ethernet) Principles of Information Systems, Seventh Edition 36

Communications Protocols (continued) • Frame Relay • Asynchronous Transfer Mode (ATM) • Fire. Wire Principles of Information Systems, Seventh Edition 37

Wireless Communications Protocols • Bluetooth • IEEE 802. 11 b (Wi-Fi) • IEEE 802. 11 g • IEEE 802. 16 (Wi. Max) • IEEE 802. 20 (MBWA) Principles of Information Systems, Seventh Edition 38

Wireless Communications Protocols (continued) • 1 G • 2. 5 G • 3 G • Multichannel Multipoint Distribution System (MMDS) Principles of Information Systems, Seventh Edition 39

Network Switching Devices • Private branch exchange (PBX): an on-premise switching system owned or leased by a private enterprise that interconnects its telephones and provides access to the public telephone system • Bridge: a device used to connect two or more networks that use the same communications protocol • Switch: a telecommunications device that routes incoming data from any one of many ports to a specific output port that will take the data toward its intended destination Principles of Information Systems, Seventh Edition 40

Network Switching Devices (continued) • Router: a device or software in a computer that determines the next network point to which a data packet should be forwarded toward its destination • Hub: a place of convergence where data arrives from one or more directions and is forwarded out in one or more other directions • Gateway: a network point that acts as an entrance to another network Principles of Information Systems, Seventh Edition 41

Network Basics: Basic Processing Strategies • Centralized processing: all processing occurs in a single location or facility • Decentralized processing: processing devices are placed at various remote locations • Distributed processing: computers are placed at remote locations but connected to each other via a network Principles of Information Systems, Seventh Edition 42

Communications Software • Network operating system (NOS): systems software that controls the computer systems and devices on a network and allows them to communicate with each other • Network-management software: enables a manager on a networked desktop to monitor the use of individual computers and shared hardware, scan for viruses, and ensure compliance with software licenses Principles of Information Systems, Seventh Edition 43

Telecommunications Applications • Linking personal computers to mainframes and networks • Voice mail • Electronic software distribution • Electronic document distribution Principles of Information Systems, Seventh Edition 44

Telecommunications Applications (continued) • Call centers • Telecommuting • Videoconferencing • Electronic data interchange (EDI) Principles of Information Systems, Seventh Edition 45

Telecommunications Applications (continued) • Public network services • Electronic funds transfer (EFT) • Distance learning • Specialized systems and services Principles of Information Systems, Seventh Edition 46

Summary • Communications: the transmission of a signal by way of a medium from a sender to a receiver • In telecommunications, the sender transmits a signal through a transmission medium such as a cable • Transmission media types: twisted-pair wire cable, coaxial cable, fiber-optic cable, microwave, cellular, and infrared • Telecommunications carriers can be divided into local exchange carriers, competitive local exchange carriers, and long-distance carriers Principles of Information Systems, Seventh Edition 47

Summary (continued) • A computer network consists of the communications media, devices, and software needed to connect two or more computer systems and/or devices • Network types: personal area network (PAN), local area network (LAN), metropolitan area network (MAN), wide area network (WAN), and international network • Network topologies: ring, bus, hierarchical, star, and hybrid • Options for how computers on a network connect: terminal-to-host, file server, and client/server Principles of Information Systems, Seventh Edition 48

Summary (continued) • Communications protocols include the Open Systems Interconnection (OSI) model, Transmission Control Protocol/Internet Protocol (TCP/IP), IEEE 802. 3 (Ethernet), etc. • Network switching devices: private branch exchange (PBX), bridge, switch, router, hub, and gateway • Examples of telecommunications applications are voice mail, electronic software distribution, telecommuting, videoconferencing, electronic funds transfer, and distance learning Principles of Information Systems, Seventh Edition 49