Bài giảng Introduction to MIS - Chapter 3: Networks and Telecommunications

Introduction to MISChapter 3Networks and TelecommunicationsJerry PostTechnology Toolbox: Creating Web PagesTechnology Toolbox: Transferring FilesCases: Wholesale SuppliersOutlineWhat is the value of a single computer? Why are computer networks so important in today’s businesses?What components do you need to install to create a network?How can multiple users share a single network?How is it possible that you can connect your computer to a network at the office, at home, or while on the road, even overseas?What is the Internet, how is it controlled, and how does it work?Are personal computers necessary anymore? What problems are you likely to encounter if you need to connect to a supplier in a different country?NetworksTeamworkCommunicationSchedulingSharingInternetSuppliersCustomersBanksInternalExternalServicesApplicationsResearchHostingSharing Data: TransactionsDatabase ManagementSystem and Web ServerOr Point-of-Sale systemInternetTeam DocumentFile Server and DatabaseReport andCommentsSharing Data: Decisions & CollaborationDecisions & collaborationTeamwork & joint authorshipSharing Data: E-mailInternet1. User creates e-mail message.2. Message transferred to account on server.3. Transferred via the Internet to the destination account.4. Message received when user checks e-mail.Sharing Data: Calendars 8:00 Mgt meeting 8:30 (open) 9:00 Staff meeting 9:30 Staff meeting10:00 new meetingHardware SharingCorporate orexternal computeraccessServerShared PrinterWorkstationstape drive(backup)PrintersStorageProcessorsFiles are transferred from workstations to the server.Software automatically copies files to tapes.LAN administrator can restore files if needed.Network ComponentsComputersServersWork stationsMediaCablesFiber opticRadioInfraredConnection devicesLAN cardLAN cardLAN cardLAN cardShared PrinterServerPersonal ComputerPersonal ComputerRouterInternetFirewallSwitchServer ScalabilityIBM Blue Gene/LIBM PS700 ExpressHPIncreasing performance within a product family.Server farms distribute the workload. Add more computers for more power.Rack mount server farm.IBM PS702 Express(multiple blades)https://asc.llnl.govNetwork Transmission MediaRadio or Micro WavesExample:Cellular phonesglass or plasticFiber Optic CableExample:Long distance phone linesantennaTwisted PairExample:Local phone linesreflective claddingCoaxialExample:Cable TVFiber OpticsFasterMore dataLess magnetic interferenceLong stretches without repeaters900 copper wires can be replaced by one fiber optic line (for telephone connections).Frequency SpectrumAll waves have similar elementsSoundRadioMicroLightFrequency differencesAmount of dataDistanceInterference / NoiseELFVLFLFMFHFVHFUHFMicrowaveOptical1001K100K1M10M100M1G10GHertzNavy/submarinesTV: 220M - 500 MHzAM: 550K - 1650 KHzPublic Safety: 150M - 160 MHzPublic Safety: 460M - 500 MHzCellular phones: 800 MHzCordless phones (some): 900 MHzPers. Com. Sys (PCS): 1.85 G - 2.2 GHz PCS ET: 2 GHzTV: 54M - 216 MHzFM: 88M - 108 MHz TechnologiesCellphone or WiMax2-10 miles, 128 kbps - 10 mbps (4G)Wi-Fi50-200 feet11 mbps - 250 mbpsBluetooth10-30 feet2.1 mbps3.0: 24 mbpsUltra-wideband10-30 feet1 gbpsLocal Area NetworksNameFormatSpeed (mbps)10Base-TTwisted pair10100Base-TTwisted pair100Gigabit EthernetTwisted pair1000Wireless LAN 11b,a,gWireless11-54Wireless LAN 11nWireless150-200LAN/fiber FDDIFiber optic100LAN/fiber ATMFiber optic155LAN/fiber high-endFiber optic100,000,000 (100 terabits)Internet ConnectionsNameFormatSpeed (mbps)Estimated CostDial-upTwisted pair0.05$20/monthDSLTwisted pair3+ down/0.5+ up $50/monthCable modemCoaxial6+ down/1+ up$50/monthSatelliteMicrowave1.5 down/0.25 up$50/monthWireless/Wi-MaxMicrowave1.5-6 down/0.25+ up$40/monthT1-leaseTwisted pair1.544$400-$700/monthT3-leaseFiber optic45 $2,500-$10,000/monthATMFiber optic155$15,000-30,000/monthOC-3Fiber optic155$16,000-$20,000/monthOC-12Fiber optic622$20,000- $70,000/monthOC-48Fiber optic2,488$50,000 - ?/monthOC-192Fiber optic9,953OC-768/futureFiber optic39,813Transmission CapacityThe Importance of BandwidthFor interesting Internet connections at specific buildings: NetworksThe need for standardsA changing environmentBackbone fiber opticHubSwitchHubRadio-based networkInternetRouters or SwitchesBuilding 1Building 2Enterprise NetworkSwitchServersWorkstations/PCsFiber opticInternet – ISPFirewallSubsidiaryAll data is converted to packets.Packet has data, destination, and source address.Switched services.Packets routed as needed.Reassembled at destination.VoiceComputerSent as packets: 1 2 3 4 5Sent as packets: A B C D EChicagoNew YorkDallasAtlantaE4CB2A15D3Packet-Switched NetworksShared ConnectionsWith shared connections, machines have to take turns, and congestion can slow down all connections.With switched connections, each computer has the full bandwidth of the connection at all times. Performance depends on how fast the switch can handle connections.Switched NetworkSwitchServersWorkstations/PCsShared-Media NetworkShared MediaTapTime DivisionABDCtimeACACAComputers A and B split their messages into packets and sharethe transmission medium by taking turns sending the data.Frequency DivisionABDCfrequency3500 HzACComputers A and B split the frequency: A uses a higher spectrum.By listening only to the assigned frequency, multiple transmissionscan occur at the same time.Spread SpectrumABDCfrequencytimeSharing a medium by both frequency and time is one methodof spread spectrum transmission. It is efficient for many computersbecause the full bandwidth can be utilized over time and frequency.Wireless CommunicationMicrowave transmissions are used to provide communications for cellular phones and laptop computers. As prices of phones, portable computers, and communication costs decrease, increasing numbers of workers are choosing wireless technologies.Managing Shared NetworksPhone or CableCompany/ISPShared: 1.5 mbps1. Each person views simple data/Web pages.Capacity is not pressed. Usage is even.2. One person views 1mbps streaming video.Capacity is pressed. All traffic slows down.Is this person a “bandwidth hog?”Options for Managing TrafficPrioritizing TrafficSlow down some users—perceived hogs.Slow down based on type of traffic.Packeteer—open packets to identify.Connection port (rare, not very useful).Sell quality of service (rare yet).Pricing mechanisms with data capsOverage feesDifferential pricingTime-of-day pricing (rare yet).Potential problem as speeds increase (4G cell).Government Interference or Necessity?“Network Neutrality” ProposalPotential problem: A commercial network might intentionally slow down traffic from a rival. For instance, Comcast (network) owns NBC (content) (January 2011). What if it slows down traffic for competitor content?But does “neutrality” mean that networks cannot manage their usage?Are network and cell phone ads misleading?Watch movies on your cell phone.Do it on 4G and see how quickly you exceed the data cap.What are actual network speeds?FCC says perhaps half in 2010. (PDF)Data CapsCap: 5 GBTransfer rate: 5 mbps5,000,000,000 Bytes8 bitsByte40,000,000,000 bits1 5,000,000 bits/sec8,000 seconds1 60 sec/minute133.33 minutesTCP/IP Reference ModelMessageHeader 3Trailer 3MessageHeader 3Trailer 3MessageHeader 3Trailer 3MessageHeader 2Trailer 2Header 3Trailer 3MessageHeader 3Trailer 3MessageHeader 2Trailer 2Header 1Trailer 14. Application3. Transport (TCP)2. Internet (IP)1. PhysicalTCP/IP ReferenceApplicationMail, Web, FTPAuthentication, compression, user servicesTransportPacketize data and handle lost packetsEstablish connections through numbered portsInternet Protocol (IP)Route packets to destinationRequires unique host addresses: IPv4=32-bit; IPv6=128-bitRequires standards and cooperationSubnetPhysical connectionsTransfers bits with some form of error correctionISO-OSI Reference ModelApplicationPresentationSessionTransportNetworkData LinkPhysicalLayer 7Layer 6Layer 5Layer 4Layer 3Layer 2Layer 1ApplicationPresentationSessionTransportNetworkData LinkPhysicalPhysical MediaOriginal DataTranslateSign on and resourcesData PacketRAdd routing dataRACAddresses &Error CheckRACRACThe InternetIntroduction to the InternetNo controlServicesE-MailTelnetFTPWWWWEB searchingGoogleYahooBing/MicrosoftHow the Internet WorksIndividualInternetserviceprovider (ISP)PhonecompanyNetworkserviceprovider (NSP)BackbonenetworkPhonecompanyCompanyWeb siteDial-up: 33.3 - 56 KbpsISDN: 128 KbpsDSL: 256 Kbps - 6 MbpsCable: 1.5 MbpsCablecompanyT1: 1.544 MbpsT3: 44.736 MbpsOC3: 155.52 MbpsOC12: 622 MbpsInternet ConnectionsSome backbone providersAT&TLevel 3Verizon (UUNet)SprintQwestPSINet/CogentGlobal CrossingCable & Wireless companiesRegional Bell operating companies (RBOCs) (3)Competitive local exchange carriers (CLECs) (new)Cable companiesCablevisionComcastRegionalCell phones/MobileSatelliteDirect SatelliteWild Blue/Starband/HughesColocation and Hosting CompaniesGeneral Data CentersMultiple high-speed Internet connections, power with UPS, air conditioning, and securityEquinixCyberconSavisTelecity (Europe)Specialty Hosting CompaniesIndividual contracts to perform specific tasks including hosting.IBMAT&TEDSThousands of small, regional providersDistributed Content through AkamaiInternetContent VideoCompany ServerAkamai Servers distributing your content to servers at the “edge” of the Internet, customers retrieve data from multiple points, reducing the load on your server and Internet connection.Voice Over IP (VoIP)InternetVoice to IPCable modemVoIP ProviderTelephone Co.SkypeVopium (Dutch)VonageNetwork Address Translation (NAT)Web Server10.1.30.15Translate:10.1.30.15=138.9.1.15Disallow incomingpeer-to-peerDomain Name System RegistrationInternet WorldReal WorldDNS Registration207.46.250.222www.microsoft.comMicrosoft CorporationOne Microsoft WayRedmond, WA 98052USInternic.orgISPNet Range207.46.0.0 – 207.46.255.255Microsoft-Global-NetArin.netInternet entities are anchored to the real world through the DNS registration and through their ISP.If they tell the truth!Domain NamesServer.Department.Company.TLDRequiredOptionalRight-to-leftOriginal TLDsSet by ICANNcomorgnetedugovmilMany more today +Country Codesaccounts.citibank.com.xqioajfm.aka82.comThis address is NOT owned by Citicorp.When you see it in an e-mail message, you know it is a fake.Internet2High speed (1 gbps or better)Quality of Service (QoS)Primarily educational and researchRequires fiber connectionBasic costsConnection (1gbps) $250,000 per yearMembership about $60,000 per yearIt is not designed for commercial Web sitesM-CommerceInternet access everywhereCell phonesTabletsLaptopsGreat potentialLimited usabilityBetter than voice?Cell Phones and Wireless CommunicationWireless cells work by handing off the wireless connection to the next tower as the caller moves.Connections to multiple towers at one time enables the system to triangulate to get a fairly precise location of the cellular device--even when it is not in a call.Location knowledge will make it possible (although perhaps not desirable) to offer new business opportunities as people move into range.Cloud ComputingDisplay browser applicationServer and dataCloud Computing: Lease v. BuyHardwareSoftwareSupport personnelFixed v. Monthly costsSecuritySimilar concepts to “outsourcing” covered in Chapter 13Global TelecommunicationsTechnical problemsMultiple standardsLanguageDeveloping nationsTime zonesLimits to space & wavesPolitical complicationsTransborder data flowsTaxesPrivacyAccessibilityCultural issuesWhat is an object?Management & controlTechnology Toolbox: Creating Web PagesSample HTML PageSection OneThis is a sample paragraph on a sample page.HTMLTables for LayoutPage EditorsImages are bitmaps: GIF, JPEG, PNGAdobe PDFQuick Quiz: Creating Web PagesCreate a document to do the following in HTML:1. Display a word or phrase in boldface.2. Link a style sheet to an HTML page.3. Display a table with three rows and four columns.4. Display a numbered list of five items.5. Display an icon in GIF format with a transparent background.Technology Toolbox: Transferring FilesConnectionStrengthsWeaknessesFTPInexpensive and easy to use.Need to find secure version.WebDAVInternet standard and can be secure.Web server security is weaker by allowing directory browsing.VPNSecure if encrypted all the way to the Web server.Difficult to configure the server side and the client needs to connect separately to the VPN.Web uploadEasy to use. HTML 5 might make it easier.Need server code to handle the file transfers and updates. Still need a secure Web site for login.Quick Quiz: Transferring Files1. Which methods can you use to transfer files to a university server?2. Why is FTP considered a security threat?3. How do you upload files to sites like YouTube?Cases: Wholesale Suppliers