1 Alter – Information Systems

© 2002 Prentice Hall

Networks and Telecommunications

Alter – Information Systems© 2002 Prentice Hall2

Opening Case: FedEx

Tracks each package through each step from shipper to recipient

Expanded into being a fully integrated corporate partner that picks up, transports, warehouses, and delivers a customer’s finished goods

E-business tools

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Applying Telecommunications in Business

TELECOMMUNICATIONS – the transmission of data between devices in different locations

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Vital Role of Telecommunications in E-Business

Telecommunications essential to: E-retailers E-marketplaces Internet content providers Internet service providers (ISPs) Application service providers (ASPs) Telephone and cable companies Telecommunication equipment manufacturers Internet and telecommunications software

firms

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Convergence of Computing and Communications

Reliance of telecommunications on computers

Role of telecommunications in computing New wired and wireless transmission New combinations of data and computing

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Figure 10.1

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Figure 10.2

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Types of Networks

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A Typical Home Network Figure 10.3

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A Local Area Network (LAN) in a Business LANs connect PCs and other equipment

within a local area Benefits:

Sharing equipment Sharing personal files Sending messages Sharing databases Administering software

Usually wired, but may also be wireless

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Figure 10.4

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A Telephone Network: Figure 10.6

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The Internet (From a User’s Viewpoint): Figure 10.7

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A Wide Area Network (WAN)

WANs are networks that span a wide geographical area

Many uses, e.g., Form the communication backbone for large

distributed organizations Focus on particular transaction processing

application(s) Transfer and consolidate corporate data, etc.

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Figure 10.8

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Functions and Components of Telecommunication Networks

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Basic Terminology

NetworkNetwork = a set of devices and communications channels Devices are called nodesnodes

ConnectivityConnectivity = the ability to transmit data between devices at different locations

SwitchingSwitching = the process of directing a signal from its source to its destination

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Channel Channel = a path along which data are transmitted Wired or wireless

DecodingDecoding = converting the data back into their original form upon arrival at its destination

Network managementNetwork management = the process of monitoring the network’s operations, detecting and repairing faults, and balancing traffic

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Figure 10.9

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Generating and Receiving Data

An ever increasing number of different types of devices can be connected to a network General purpose Special purpose

Front-end processor – a specialized computer that handles network traffic for another computer Improves the efficiency of the overall system

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Transmitting Analog versus Digital Data

Data transmission requires that data be encoded as electrical or optical signals, and then decoded at destination

Two important factors: Are the original data analog or digital? Are the data transmitted in analog or digital

form?

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Analog data, analog signal Original signal added to a carrier signal Used for voice communication

Analog data, digital signal Data must be digitized The digitized data are only an approximation of

the original The quality depends on the precision of the

digitizing process

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Digital data, analog signal Must use a modemmodem at each end

Superimposes a pattern of 0s and 1s on the carrier signal

Digital data, digital signal Modems are no longer needed Digital subscriber line (DSL)

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Significance of analog vs. digital transmission Digital technology improves the quality of the

transmission Digital coding allows for error detection and

correction Digital data can be readily manipulated

High definition television (HDTV)

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Directing Data From Source to Destination

Dedicated lineDedicated line – a telephone line leased by a firm, and used exclusively by that firm

SwitchSwitch – a special purpose computer that directs incoming messages along a path

Private branch exchange (PBX)Private branch exchange (PBX) – a special-purpose computer that distributes calls within a customer’s site

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Circuit Switching vs. Packet Switching

CIRCUIT SWITCHINGCIRCUIT SWITCHING: The method used in telephone networks Sets up a temporary circuit between the

source and the destination Resources are reserved for the duration of

the session (call)

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PACKET SWITCHINGPACKET SWITCHING: Appropriate when data are transmitted

infrequently from a large number of nodes Used on the Internet

The message is divided into packets containing control information

No circuit is established Provides better sharing of resources

Multiple users share the same resources

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Figure 10.13

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Transmitting Data Through Wire and Wireless Media

Bandwidth – corresponds to the capacity of the transmission channel Mbps or Gbps A major limitation for the information

superhighway

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Wired Transmission

TWISTED PAIRTWISTED PAIR Used for voice transmission and for low

volume data transmission Slow

COAXIAL CABLECOAXIAL CABLE Used in LANs and for data transmissions of

less than 10 miles Faster and more versatile than twisted pair

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FIBER OPTICFIBER OPTIC Carries data in the form of light Extremely fast Very light Very difficult to tap into Very little data loss Costly

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Wireless Transmission Figure 10.16

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Telecommunications Standards

De facto standards – established by the fact that a product dominates the market, e.g., Windows

De jure standards – defined by industry groups or by the government

Many de facto standards become de jure standards

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The OSI (open systems interface) OSI (open systems interface) modelmodel is a framework for defining telecommunications standards Covers all aspects of network operations and

management Developed by the International Standards

Organization (ISO) Each level in the model is implemented

through protocols

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Figure 10.18

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TCP/IP (Transmission Control Protocol/ Internet Protocol) Used on the Internet Five layer model HTML and HTTP are examples of application

layer standards Open vs. proprietary standards

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More About Network Technology

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More About LANs

Main topologies: StarStar – all messages go through a central

node that serves as a switch RingRing – the nodes are linked directly in a

closed loop Bus Bus – each node is attached to a central

channel called a bus

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Token passing: One of the most common methods for internal

communication Used in ring topologies Token – a bit pattern that circulates between

the nodes To transmit data, a node appends it to the

token

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LANs use two types of transmission: BasebandBaseband – the entire capacity of the cable

is used to transmit a single digitally encoded signal

Ex.: Ethernet BroadbandBroadband – the capacity of the cable is

divided into separate frequencies to permit it to carry several signals at the same time

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Interconnection devices – a combination of hardware and software: Routers Bridges Gateways

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More About WANs

Virtual private networks (VPNs)Virtual private networks (VPNs): A private network configured within a public

network Can be built on top of the Internet Service offered by the telephone companies

and ISPs

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Value added networks (VANs)Value added networks (VANs):: Public data networks that “add value” by

transmitting data and by providing access to commercial databases and software

Use packet switching Subscription based Often used in electronic data interchange

(EDI) systems

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Public switched data network technologies Public switched data network technologies (PSDN)(PSDN) Data flows through a public network

managed by a telecommunications carrier Most common technologies:

ISDN (integrated service digital network) X.25 Frame relay Asynchronous transfer mode (ATM)

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Wireless Networking

Wireless application protocol (WAP) - a standard technology framework for wireless Internet Allows for some of the Internet content to be

accessed by mobile devices Bluetooth – a fast short-range wireless

technology Wireless office

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IP Telephony

Voice over the Internet Limited by the packet switching technology

currently used by the Internet

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Telecommunications Policy

Why should the government permit only some companies to sell products in a particular line of business?

What should be the rationale for regulating telecommunications and setting prices?

Who should be able to use specific public resources, such as radio frequencies?

To what extent is universal access possible and to what extent should it be guaranteed?