Technology Internet, and Wireless · Method of slicing digital messages into parcels (packets),...

7.1 © 2010 by Pearson

7Chapter

Telecommunications, theInternet, and Wireless

Technology


LEARNING OBJECTIVES

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Identify the principal components of telecommunicationsnetworks and key networking technologies.

Describe the main telecommunications transmission media andtypes of networks.

Explain how the Internet and Internet technology work and howthey support communication and e-business.

Identify the principal technologies and standards for wirelessnetworking, communication, and Internet access.

Assess the value to business of radio frequency identification(RFID) and wireless sensor networks.

Management Information SystemsChapter 7 Telecommunications, the Internet, and Wireless Technology


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What is a computer network?Two or more connected computersMajor components in simple network

Client computerServer computerNetwork interfaces (NICs)Connection mediumNetwork operating systemHub or switchRouter


Telecommunications and Networking in Today’s Business World


Components of a Simple Computer Network

Figure 7-1

Illustrated here is a very simple computer network, consisting ofcomputers, a network operating system residing on a dedicated servercomputer, cabling (wiring) connecting the devices, network interfacecards (NIC), switches, and a router.




Network Devices


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Networks in large companiesComponents can include:

Hundreds of local area networks (LANs) linked to firmwidecorporate networkVarious powerful servers

Web siteCorporate intranet, extranetBackend systems

Mobile wireless LANs (Wi-Fi networks)Videoconferencing systemTelephone networkWireless cell phones




Corporate Network Infrastructure

Figure 7-2

Today’s corporatenetwork infrastructureis a collection of manydifferent networks fromthe public switchedtelephone network, tothe Internet, tocorporate local areanetworks linkingworkgroups,departments, or officefloors.




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Key digital networking technologies

Client/server computingDistributed computing model

Clients linked through network controlled by networkserver computer

Server sets rules of communication for network andprovides every client with an address so others can find iton the network

Has largely replaced centralized mainframe computing

The Internet: Largest implementation of client/servercomputing




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Packet switchingMethod of slicing digital messages into parcels (packets),sending packets along different communication paths asthey become available, and then reassembling packets atdestination

Previous circuit-switched networks required assembly ofcomplete point-to-point circuit

Packet switching more efficient use of network’scommunications capacity




Ethernet Frame StructureIEEE 802.3 Ethernet frame

Preamble: 8 bytes7 bytes with pattern 10101010, followed by one bytewith pattern 10101011 (frame delimiter) used to synchronize receiver, sender clock rates

Addresses: 6 bytes, frame is received by all adapters on a LAN anddropped if address does not matchType (Length): 2 bytes, length of data segment (min. 46 bytes)CRC (Cyclic Redundancy Check): 4 bytes, created by sender,checked by receiver, if error detected, the frame is simply dropped

Type

64 – 1518 bytes in length


Packet-Switched Networks and Packet Communications

Figure 7-3Data are grouped into small packets, whichare transmitted independently over variousCommunications channels and reassembledat their final destination.




Packet-Switched Networks and Packet Communications




LAN Standards

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LAN technologies are standardized by theInstitute of Electrical and ElectronicsEngineers (IEEE) Project 802 – Local

Network StandardsIEEE 802.3 specifies the standards forEthernet wired local area networks

How devices physically signal each other, howdevices “share the wire in the wall”, etc.

Ethernet is the de facto standard for wiredLAN in use today


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TCP/IP and connectivityConnectivity between computers enabled by protocolsProtocols: Rules that govern transmission of informationbetween two pointsTransmission Control Protocol/Internet Protocol (TCP/IP)

Common worldwide standard that is basis for InternetDepartment of Defense reference model for TCP/IP

Four layersApplication layerTransport layerInternet layerNetwork interface layer




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Signals: digital vs. analogModem: Translates digital signals into analog form

Types of networksLocal-area networks (LANs)

Client/server or peer-to-peerEthernet – physical network standardTopologies: star, bus, ring

Campus-area networks (CANs)

Wide-area networks (WANs)

Metropolitan-area networks (MANs)

Communications Networks



Functions of the Modem

Figure 7-5

A modem is a device that translates digital signals from acomputer into analog form so that they can be transmitted overanalog telephone lines. The modem also translates analog signalsback into digital form for the receiving computer.




Physical Topology

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The arrangement of devices in a network is referred toas its physical topology

Star: central connection pointRing: attached to 2 neighborsBus: common, shared backboneMesh: multiple interconnectionsTree: stars on a bus

Two similar networks canbe connected by a devicecalled a bridge (or switch)Gateway is a generic termfor any device or softwarecode used to join two networks


Network Topologies•

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In a star topology, all devices on the network connect to a singlehub and all network traffic flows through the hub. In an extendedstar network, multiple layers or hubs are organized into ahierarchy.In a bus topology, one station transmits signals, which travel inboth directions along a single transmission segment. All of thesignals are broadcast in both directions to the entire network. Allmachines on the network receive the same signals, and softwareinstalled on the client’s enables each client to listen formessages addressed specifically to it.A ring topology connects network components in a closed loop.Messages pass from computer to computer in only one directionaround the loop, and only one station at a time may transmit. Thering topology is primarily found in older LANs using Token Ringnetworking software.


Network Topologies

Figure 7-6

The three basicnetwork topologies arethe bus, star, and ring.




Ethernet

On an Ethernet,data travels on afirst come, firstserved basis. Iftwo workstationsattempt to senddata at the sametime, a collisionoccurs.That data mustbe resent.


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Physical transmission mediaTwisted wire (modems)Coaxial cableFiber optics and optical networks

Wireless transmission media and devicesMicrowaveSatellitesCellular telephones

Transmission speedHertzBandwidth




Twisted PairTwo or more pairs of insulated copper wires twistedtogether and may be shielded (STP) or unshielded(UTP). It has the lowest capacity of the cableoptions

CoaxialContains a solid inner copper conductor surrounded byinsulation and outer braided copper or foil shield. Itcomes in different thicknesses and is higher capacitythan twisted pair

Fiber-OpticMade of light-conducting glass or plastic core,

surrounded by more glass, called cladding, and atough outer sheath. It is high capacity and is mainlyused in high speed backbones

Physical transmission mediaWired Media


MicrowaveA high frequency radio signal that is sent through the airusing either terrestrial (earth-based) or satellite systems

Terrestrial MicrowaveA line-of-site technology(unobstructed) used to crossinaccessible terrain or toconnect buildings where cableinstallation would beexpensive. Attenuation is lowover short distance but higherover longer distances, and highwinds, heavy rain, EMI andeavesdropping are alsoproblems

Wireless transmission mediaand devices


Satellite MicrowaveA line-of-site technologythat uses relay stations totransfer signals betweenantennae located on earthand a satellite orbiting theearth. It can be used toaccess very remotelocations and like aterrestrial microwave;attenuation, EMI andeavesdropping are alsoproblems

Wireless transmission mediaand devices


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What is the Internet?Connecting to the Internet

Internet service providers (ISPs)Services

DSL, cable, satellite, T lines (T1, T3)

Internet addressing and architecture

IP addresses

The domain name systemHierarchical structureTop-level domains

The Global Internet



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Today, the Internetconnects computersall over the globe andsupplies informationto people of all agesand interestsWith an estimated 200million nodes and 1billion users, theInternet is huge

Graphical visualization of a small part of the Internet today.


The Domain Name System

Figure 7-8The Domain Name System is ahierarchical system with a rootdomain, top-level domains, second-level domains, and host computersat the third level.


The Global Internet


Network Links

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A communications channel, or link, is aphysical path or frequency for signaltransmissionsBandwidth is the transmission capacity ofa communications channel (usuallyexpressed in bits/sec, bps)

BroadbandNarrowband


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Internet ArchitectureTrunk lines (backbone networks)Regional networksISPs

Internet GovernanceNo formal managementPolicies established by professional, government organizations

IAB, ICANN, W3C

The Future InternetIPv6Internet2, NGI

The Global Internet



Internet Network Architecture

The Internet backboneconnects to regionalnetworks, which in turnprovide access to Internetservice providers, largefirms, and governmentinstitutions. Networkaccess points (NAPs)and metropolitan areaexchanges (MAEs) arehubs where the backboneintersects regional andlocal networks and wherebackbone ownersconnect with one another.


The Global Internet


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Internet servicesE-mailChatting and instant messagingNewsgroupsTelnetFile Transfer Protocol (FTP)World Wide Web

Voice over IP (VoIP)Unified communicationsVirtual private networks (VPNs)


The Global Internet


Client/Server Computing on the Internet

Figure 7-10Client computers running Web browserand other software can access an arrayof services on servers over the Internet.These services may all run on a singleserver or on multiple specialized servers.


The Global Internet


How Voice over IP Works

An VoIP phone call digitizes and breaks up a voice message into data packets that maytravel along different routes before being reassembled at the final destination. A processornearest the call’s destination, called a gateway, arranges the packets in the proper orderand directs them to the telephone number of the receiver or the IP address of the receivingcomputer.


The Global Internet


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The World Wide WebHTML (Hypertext Markup Language):

Formats documents for display on WebHypertext Transfer Protocol (HTTP):

Communications standard used for transferring Webpages

Uniform resource locators (URLs):Addresses of Web pagesE.g., http://www.megacorp.com/content/features/082602.html

Web serversSoftware for locating and managing Web pages


The Global Internet


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IntranetsUse existing network infrastructure with Internet connectivitystandards software developed for the WebCreate networked applications that can run on many types ofcomputersProtected by firewalls

ExtranetsAllow authorized vendors and customers access to an internalintranetUsed for collaborationAlso subject to firewall protection


The Global Internet


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Wireless devices

PDAs, BlackBerry, smart phones

Cellular systemsCompeting standards for cellular service

United States: CDMA

Most of rest of world: GSM

Third-generation (3G) networks

Higher transmission speeds suitable for broadband Internetaccess

The Wireless Revolution



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Wireless computer networks and Internet accessBluetooth (802.15)

Links up to 8 devices in 10-m area using low-power, radio-based communication

Useful for personal networking (PANs)

Wi-Fi (802.11)

Set of standards: 802.11a, 802.11b, 802.11g, 802.11n

Used for wireless LAN and wireless Internet access

Use access points: Device with radio receiver/transmitterfor connecting wireless devices to a wired LAN




A Bluetooth Network (PAN)Figure 7-15

Bluetooth enables avariety of devices,including cell phones,PDAs, wirelesskeyboards and mice,PCs, and printers, tointeract wirelessly witheach other within asmall 30-foot (10-meter)area. In addition to thelinks shown, Bluetoothcan be used to networksimilar devices to senddata from one PC toanother, for example.




An 802.11 Wireless LANFigure 7-16

Mobile laptop computersequipped with wirelessnetwork interface cardslink to the wired LAN bycommunicating with theaccess point. The accesspoint uses radio waves totransmit network signalsfrom the wired networkto the client adapters,which convert them intodata that the mobiledevice can understand.The client adapter thentransmits the data fromthe mobile device back tothe access point, whichforwards the data to thewired network.




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Wireless computer networks and Internet accessWi-Fi (cont.)

Hotspots: One or more access points in public place toprovide maximum wireless coverage for a specific area

Weak security features

WiMax (802.16)

Wireless access range of 31 miles

Require WiMax antennas

Sprint Nextel building WiMax network




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Radio frequency identification (RFID)

Use tiny tags with embedded microchips containing dataabout an item and location, and antenna

Tags transmit radio signals over short distances to specialRFID readers, which send data over network to computer forprocessing

Active RFID: Tags have batteries, data can be rewritten,range is hundreds of feet, more expensive

Passive RFID: Range is shorter, also smaller, less expensive,powered by radio frequency energy




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Radio frequency identification (RFID)Common uses:

Automated toll-collection

Tracking goods in a supply chain

Requires companies to have special hardware and software

Reduction in cost of tags making RFID viable for many firms




How RFID Works

RFID uses low-powered radio transmitters to read data stored in a tag at distancesranging from 1 inch to 100 feet. The reader captures the data from the tag and sendsthem over a network to a host computer for processing.




RFID


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