Mit6e Ch04 by Firli

8/6/2019 Mit6e Ch04 by Firli

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Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 1

Managing Information Technology6th Edition

CHAPTER 4

TELECOMMUNICATIONS ANDNETWORKING


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IT Building Blocks

Building Blocks of InformationTechnology

Hardware Software Network Data


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Overview of Telecommunications and

Networking

The electronic linking of geographically disperseddevices required to accomplish telecommunications

Networking

Communication at a distance. Also synonymous withdata communications, datacom, teleprocessing,telecom, and sometimes networking.

Telecommunications


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The Telecommunications Industry

Three major segments Carriers who sell the service of communication

transmission Equipment vendors who manufacture and sell

telecommunications hardware and software Service Providers who provide access to or

services via the Internet


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Telecommunications Industry

AT&T Largest corporation in industry In 1984, AT&T split into several companies as a result

of a US Department of Justice antitrust lawsuit Breakup of AT&T has led to innovation through

competition

Recent trend towards consolidation in the industry


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Overview of Telecommunications andNetworking

Telecommunications and networking arebecoming increasingly important tobusinesses because of decentralization andglobalization

The short answer is thatnetworks will change everything"

- Paul Saffo


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Reasons for Networking

Five primary reasons for networking1. Sharing of technology resources

Prior to networking capabilities, computers could not even shareprinters!!

2 . Sharing of dataEnables virtual teams who can share dataAllows efficient transactions between businesses, their suppliers,their and customersSome businesses share many terabytes of data per day

3 . Distributed data processing and client/server systems4. Enhanced communications5 . Marketing outreach


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Five primary reasons for networking1. Sharing of technology resources2 . Sharing of data

3 . Distributed data processing and client/server systemsDistributed data processing

Information processing that uses multiple computers at multiple sitesthat are tied together through telecommunication lines

Client/Server Systems A type of distributed systems in which the processing power is

distributed between a central server and a number of client computers4. Enhanced communications5 . Marketing outreach

Client ServerTransfer of Data


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Five primary reasons for networking1. Sharing of technology resources2 . Sharing of data3 . Distributed data processing and client/server systems

4. Enhanced communicationsTelecommunication networks provide the ability to communicationthrough Email, Bulletin Boards, Blogs, Instant Messaging, Wikis, andVideoconferencingLinks between organizations can lead to strategic advantages interms of business transactions

SABRE airline reservation system EDI5 . Marketing outreach

Businesses may share data with consumers to advertise or sell theirproducts through a corporate web presence


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Overview of Telecommunications andNetworking

A telecommunications network is more than aseries of wires or radio wavesFunctions of a Telecommunications Network

Table 4.1


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Analog and Digital Signals

A signal in which some physical propertycontinuously varies across time

Analog Signals

A signal that is not a continuous function of time, butrather a series of discrete values that represent onesand zeros

Digital Signals


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Representation of digital and analog signals

Figure 4.2


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Digital computer data does not naturally meshwith analog transmission; it must be convertedfrom ones and zeros to analog signals

Solutions Modem (Modulator/Demodulator)

Digital networksAdvantages of lower error rates and higher speeds

Figure 4.1


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Transmission SpeedTransmission speeds can be measured inseveral ways

The difference between the highest and lowest frequencies thatcan be transmitted on a single medium; a measurement of capacity

Bandwidth

Cycles per second

Hertz

Signals per second

Baud


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Telecommunication Lines

Types of Transmission Lines Private (dedicated)

Advantages

Ensures quality of transmissionDisadvantages

Costly

SwitchedAdvantages

Less costlyDisadvantages

Message may take many different routes Quality of transmission may degrade


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Telecommunication Lines

Types of Transmission Lines

Data can only travel in one direction

Simplex

Data can travel in both directions, but not simultaneously

Half-duplex

Data can travel in both directions at once

Full-duplex


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Transmission Media

Twisted Pair Literally wires that are twisted to reduce

interference Can be shielded (STP) or unshielded (UTP), but the

most commonly used is UTP Commonly used in telephones and LANs


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Transmission MediaCoaxial (Coax) Cable Baseband

Inexpensive, designed for digital transmission

BroadbandOriginally for analog, now used for digitalCommonly used in television cable

Figure 4. 3


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Transmission Media Wireless

Not strictly a transmission media, but rather a technology in whichradio signals are sent through the airThere are many different wireless technologies such as cordlesstelephones and cellular telephones which are widely used in personaland business communicationsWe will consider the following wireless technologies in more detail:

Wireless LANsMicrowave

Line of sightSatellite

Long distances Line of sight

RFID Bluetooth


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Copyright 2009 Pearson Education, Inc. Publishing as Prentice Hall 2 0

Transmission Media

Wireless Wireless LANs

Growing in popularityUseful when wiring is not possibleSlower than some wired solutionsAllow mobile devices to connect to network


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Transmission Media

Wireless Microwave

Widespread use for several decadesLine of sight transmissionLimited to 25 -5 0 mile distances because of curvature of the earthExpensive, but less costly than fiber optic cables


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Transmission Media

Wireless Satellite

Geostationary Earth Orbit (GEO) Remains stationary relative to earth Inmarsat service of 11 GEO

satellites

Low Earth Orbit (LEO)

Figure 4.4


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Transmission MediaWireless Satellite

Geostationary Earth Orbit (GEO)Low Earth Orbit (LEO)

Iridium

First major LEO project with 66 satellites Faced high operating costs and whichresulted in a bankruptcy

Mostly military subscribers Tell us more about these 3

Globalstar LEO project with 40 satellites that does not

provide global coverage Teledesic

Ambitious project with original plans tolaunch 840 satellites

This was later cut to 2 88 satellites, then 3 0,and then the program was cancelled

Figure 4.4


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Transmission Media

Wireless RFID

Acronym for Radio Frequency IdentificationAn old technology that became popular in businesswhen Wal-Mart required the use of RFID by some of itssuppliers to improve inventory and supply chainmanagement


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Transmission Media

Wireless RFID

Two Broad Types of RFID Active these tags have their own power supply and can

transmit messages continuously, on request, or on a schedule Cost over $1.00

Passive these tags only send a response the RFID readersends a small radio signal which induces a current

Cost in the $0.08 - $0. 2 0 range

Many analysts believe that passive tags must cost only$0.0 5 for RFID to be widely adopted


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Transmission Media

Wireless Bluetooth

Named after Danish King who united Denmark The technology is intended to unify telecom and computing

Short-range wireless technologyDesigned to consume very little electrical power and beproduced at a low costFound in a growing number of devices such as cell phones,laptops, headsets, keyboards, mice, and home appliances

Over3

18 million devices in2

005

used Bluetooth forcommunication between devices


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Transmission Media

Fiber Optics Thin fiber of glass Faster, lighter, and more secure than other media Large diameter fiber is multimode (multiple light

rays at the same time) while smaller diameter issingle mode

Smaller diameter fiber has larger capacity due toless light bounces


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Individual Network AccessInternet Service Providers (ISPs) sell access to the InternetEarly, the only way to access the Internet was through a dial-in modemconnectionConsumers now have more options including faster broadbandconnections

Digital Subscriber Line (DSL) is a connection through a telephone company Cable modem is a connection through a cable television company Satellite

With one-way service, individuals must obtain uplink service from another provider Wireless access may be through a municipal carrier or a private companyThere are several pricing methods for personal Internet access

Fixed price (usually monthly)Hotels and airports often offer Internet access for a shorter period (e.g., 2 4 hours) Cost based on usage (data transferred) Free to consumers, but supported by taxes or advertising


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Network TopologyNetwork topology refers to the configuration orarrangement of the devices

Figure 4. 5Bus All devices are attached to one cable Single-point failure

RingSimilar to bus, but ends are attachedNot susceptible to single-point failure

StarAll nodes are attached to central deviceSusceptible to failure of central device, but easy toidentify cable failure

TreeSimilar to the star, but with a hierarchical structure

MeshDevices are to multiple other devicesA failure has little impact on the networkCostly


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Networking DevicesDevices used to implement network topologies

Simple devices that forwards all messages to every device attached to it

Hub

Central device that connects wireless LAN to other networks

Wireless Access Point

Connects two LAN segments and only forwards messages that need to go to other segment

Bridge

A multiport bridge; connects two or more LAN segmentsSwitch

Connects two ore more LANs and only forwards messages that go to the other LAN

outer


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Network Types

There are several types of networksWe will consider six types

1. Computer Telecommunications Networks2 . Local Area Networks (LANs)3 . Backbone Networks4. Wide Area Networks (WANs)5 . The Internet6. Internet 2


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Network Types1. Computer Telecommunications Networks

This was the only type of network until the1980s

Commonly used in mainframe architectures

Figure 4. 7


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Network Types

2 . Local Area Networks (LANs)1. Contention Bus (IEEE 80 2 .3 )

Developed by Xerox

Usually called Ethernet after the original Xerox versionHalf-duplexAll devices must contend to use

CSMA/CD protocol for collisions

2 . Token Bus (IEEE 802 .4)3 . Token Ring (IEEE 802 .5 )4. Wi-Fi (IEEE 802 .11)5 . WiMAX (802 .16e)


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Network Types

2 . Local Area Networks (LANs)1. Contention Bus (IEEE 80 2 .3 )2 . Token Bus (IEEE 802 .4)3 . Token Ring (IEEE 802 .5 )

Developed by IBMCombination of ring topology with use of tokens (used

the same way as in token bus)4. Wi-Fi (IEEE 802 .11)5 . WiMAX (802 .16e)


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Network Types2 . Local Area Networks (LANs)

1. Contention Bus (IEEE 80 2 .3 )2 . Token Bus (IEEE 802 .4)3 . Token Ring (IEEE 802 .5 )4. Wi-Fi (IEEE 802 .11)

Short for Wireless FidelityMost common wireless LAN typeUses a shared Ethernet designUse CSMA/CA Protocol

Similar to CSMA/CD, but with less collisionsCommonly used in offices to supplement wired Ethernet networksor in areas where adding wiring is problematicMany cities are offering Wi-Fi networks

5 . WiMAX (802 .16e)


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Network Types

LANs1. Contention Bus (IEEE 80 2 .3 )2 . Token Bus (IEEE 802 .4)3

. Token Ring (IEEE 802

.5

)4. Wi-Fi (IEEE 802 .11)5 . WiMAX (802 .16e)

Newest of the network typesSimilar to Wi-Fi, but operates over longer distances and at

higher speedsCan use both licensed and non-licensed frequenciesSprint Nextel are planning to offer their Xohm WiMAXservice across the US in the 2 .5 GHz radio spectrum

In November 2 007 , Sprint Nextel abandoned talks of a jointventure with Clearwire, a WiMAX provider


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Network Types

Local Area Networks (LANs) Problems with wireless networks (WiFi and

WiMAX)More difficult to secure that other network typesOrganizations that offer wireless access to enticecustomers have problems with noncustomers orunprofitable customers overusing the network

Unauthorized wireless use is also problematic in condosand apartments


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Network Types

Types of Networks3 . Backbone Networks

Connect LANsKey to internetworking

Figure 4.10


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Network Types

4. Wide Area Networks (WANs) Similar to LANs, but cover greater distances We will consider the following three general types

of WANs because they each have advantages anddisadvantages

1. Switched Circuit2

. Dedicated Circuit3 . Packet-switched


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Network Types

4. Wide Area Networks (WANs)1. Switched Circuit (or circuit-switched)

A single physical path is temporarily created between two nodesfor their exclusive communication

There are most widely available means of implementing a WANusing a switched circuit connection is to use the ordinarytelephone networkAdvantages

Easy to set upDisadvantages

Low speed High error rates

There are two different pricing schemes available for this service Direct Distance Dialing (DDD) - pay for usage Wide Area Telephone Service (WATS) - fixed rate


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Network Types4. Wide Area Networks (WANs)

2 . Dedicated CircuitThese are permanent channelsexclusive to the business

Advantages High capacity Low error rates

Disadvantages Expensive

There are two different types of dedicated circuits

Leased lines are cable, microwave, orfiber connections

Satellite circuits are popular fororganizations with many global locations

Table 4.3


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Network Types4. Wide Area Networks (WANs)

3 . Packet-switchedMultiple connections exist simultaneously over the same physicalcircuitMessages are broken up into packets

Businesses use PADs (Packet assembly/disassembly devices) toconnect their networks to a common carrier network

Figure 4.11AdvantagesEfficient use of networkCan be high capacity

DisadvantagesPackets may arrive indifferent order or with delay


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Network Types

5 . The Internet Network of networks that use the TCP/IP protocol Similar to an enormous WAN

433 million hosts as of January 2 007 Roots in ARPANET and NSFNET

ARPANET (Advanced Research Projects Agency Network) wascreated by the US Department of DefenseNSFNET (National Science Foundation Network) was createdto link supercomputers for researchEach of these were wide scale, packet-switching networksthat lead to the creation of the Internet


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Network Types5 . The Internet

Internet Applications


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Network Types

6. Internet 2 Not-for-profit consortium made up of over 2 00

universities as well as industry and governmentpartners that develops and deploys advanced networkapplications and technologies for research andcommercial purposes

GoalsCreate a leading-edge network capability for the nationalresearch community

Enable revolutionary Internet applications based on a muchhigher-performance Internet than we have todayEnsure the rapid transfer of new network services andapplications to the broader Internet community


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Networking ProtocolsOSI Model Developed by the International Organization for

Standardization (ISO)to outline a standard set of protocols for telecommunications

Figure 4.14


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Networking Protocols

Transmission Control Protocol/Internet Protocol(TCP/IP) Created to link different types of networks (e.g.,

satellite and ground packet networks) together into anetwork of networks

Has become de facto standard protocol fornetworking

TCP is responsible for the reliable and ordered transmissionof messages

IP is responsible for routing individual packets based on theirindividual addresses (IP addresses)

Roughly corresponds to network and transport layersof OSI model


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Networking Crucial to Organizations

Networking and Telecommunications havebecome necessary for businesses to function Problems with undersea Internet cables cut in

Middle East


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Mit6e Ch04 by Firli

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