alter – information systems © 2002 prentice hall 1 networks and telecommunications
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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?
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