Review For FinalNetwork Architecture ModelsOSI Reference ModelSummary QuestionsInternetworkingSlide 6Fundamentals of Data & SignalsSlide 8AttenuationFrequency, Bandwidth (See Fundamentals of Data & Signals – Continued for details)Conducted and Wireless MediaSlide 12Local Area NetworksSlide 14Slide 15ServersSlide 17Slide 18File Server Program AccessSlide 20Software and Support SystemsEthernet standardsSlide 23Slide 24Automatic Inheritance of Access RightsSlide 26Wide Area NetworksSlide 28Slide 29Telecommunications SystemsSlide 31Slide 32Standard telephone lineReview For Final(Week 16, Monday 12/6/2004)Should consider Review-For-Exam4 for your Final Exam preparationNetwork Architecture Models3OSI Reference Model7 layersEach layer communicate with its peer layer, and with layer above and below it.Different protocols at each layerUpper layer deal with application issues, and are implemented in softwareLower layers handle data transport issues, and are implemented in software and hardwareApplicationData transport4Summary Questions1. (a) Name the OSI layers that deal with application issues ? (b) Name the OSI layer that deal with data transport issue ?Answer: See previous slide2) Application programs used at the application layer of the OSI Model include word processing. T / F3) Upper layers of the OSI Model are usually implemented in physical devices. T / FInternetworking6Summary Questions3. The local area network shown in Figure 8-21 (p. 273) has two hubs (X and Y) interconnecting the workstations and servers. What workstations and servers will receive a copy of a packet if the following workstations/servers transmit a message:Workstation 1 sends a message to workstation 3:Workstation 2 sends a message to Server 1:Server 1 sends a message to workstation 3:4. Replace hub Y with a switch. Now what workstations and servers will receive a copy of a packet if the following workstations/servers transmit a message:Workstation 1 sends a message to workstation 3:Workstation 2 sends a message to Server 1:Server 1 sends a message to workstation 3:Fundamentals of Data &Signals8Summary Questions1. Distinguish between digital and analog signalsAnswer: (see class notes for details):Analog: Continuous waveform, State of signal (voltage level, etc.) varies continuously among an infinite number of statesDigital: Non-continuous waveform, State of signal remain constant during each clock-cycle, Few possible states2. Distinguish between digital and binary transmissionAnswer: Digital: Few possible states Binary: 2 states9AttenuationA signal starts at a transmitter with 10 watts of power and arrived at a receiver with 5 watts of power. Calculate the loss of power in dB.1. dB = 10 log10 (P2 / P1) 2. dB = 10 log10 (5/10)3. dB = 10 log10 (0.5)4. dB = 10 (-0.3)5. dB = -3Q: What is the decibel loss of a signal that starts at 50 watts and experiences a 10-watt loss over a given section of cable ?Q: What is the decibel loss of a signal that loses half its power during the course of transmission ?10Frequency, Bandwidth(See Fundamentals of Data & Signals – Continued for details)Q: What is the frequency (in Hz) of a signal that repeats 80000 times within one minute ? Answer: 80000 / 60 = 1333.33 Hz or 1.33 MhzQ: What is the bandwidth of a signal composed of frequencies from 50 Hz to 500 Hz ? Answer: |500 Hz – 50 Hz | = 450 HzQ: What is the bandwidth of a signal composed of frequencies from -50 Hz to 500 Hz ? Answer: |500 Hz – (-50) Hz | = 550 HzConducted and WirelessMedia12Summary QuestionsWhat does cross talk interference mean ? How can crosstalk interference be reduced ?If transmission wires are placed side by side, electromagnetical radiation is emitted by one wire and picked up by the other. Twisting pair of wire reduce crosstalk interference.What categories of twisted pair are usually used in LANs ?Categories 3, 4, 5, 6, 7, 8What are the advantages and disadvantages of STP compared to UTP ?Advantage: better level of isolation from noise. Disadvantage: costWhat is the main difference between baseband coaxial cable and broadband coaxial cable ?Baseband carries digital signals, whereas broadband carries analog signals.What are the advantages of Optical fiber compared twisted pair and coaxial cable ?Speed, No significant noise, No significant interference, Long distanceCan you transmit video signal over twisted pair wire ? ExplainYou can, but noise is going to be a serious factor.Local Area NetworksSchool of BusinessEastern Illinois University14Summary QuestionsWhat are the four factors to take into account in deciding how many servers to use to implement a LAN’s services?Answer: Optimization, reliability, security, costTo what two devices does a print server connect? Answer: To a printer via a parallel cable and to a hub or switch via UTP Where does a print job go when it leaves the client PC (not counting the hub or switch)? Answer: The print job first goes to a file server, which puts it in a print queue. Do you have to use special printers for print service?Answer: You do not need special printers, because the printer is fed by a parallel cable in the normal way.15Summary QuestionsCan anyone access shared files? Answer: No. Only those who have access rights. Why does file sharing for programs make software installation easier? Answer: A program only has to be installed once, on the file server, not on each client PC.  Why is storing program files on a file server limiting? Answer: Programs stored on file servers execute on client PCs, which have limited processing power.16ServersSingle server Versus Multiple specialized Servers–Decision based on Cost, Optimization, Reliability, and SecurityOptimization: –File servers need storage capacity and rapid access–Client/Server applications need very fast processors17ServersPrint Server: basically NIC + a parallel port + Random Access Memory + Intelligence to receive data and commands from print queue manager program.Note: Possible to connect printer directly to file server, but people might have to walk far to get their printout.Newer printers have built-in NICs & print server hardware18ServersFile Server: A server that acts like a very large hard disk shared by many client PCsAdvantages: Single program installation, Sharing programs and files with access rights. Operates according to the File Server Program Access System seen during Classes