MidtermProblems - Mid-Term Exam for Computer Networks Fall...

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Mid-Term Exam for Computer Networks Fall 2008 >>> SOLUTIONS <<< Welcome to the Mid-Term Exam for Computer Networks . Read each problem carefully. There are six required problems (each worth 16 points – you get 4 points for following these instructions correctly). There is also an additional extra credit question worth 10 points. You may have with you a calculator, pencils, erasers, blank paper, and one 8.5 x 11 inch “formula sheet”. On this formula sheet you may have anything you want (definitions, formulas, homework answers, old exam answers, etc.) as handwritten by you on both sides of the sheet. Photocopies, scans, or computer generated/printed text are not allowed on this sheet. You have 75 minutes for the exam. Please use a separate sheet of paper for each question. Good luck and be sure to show your work! Problem #1 (10 minutes) Answer the following questions regarding the basics of computer networks and the Internet. a) What are the fundamental measures of a communications system? 0.5 each and round-up (3 pts total) Throughput, delay, loss, cost, mobility, robustness, and secrecy b) What are the basics tasks of a communications system? 0.5 each and round-up (4 pts total) Message formatting, error detection and recovery, addressing, routing, flow control, system management, security, and QoS c) Precisely define protocol and interface 0.5 each and round-up (3 pts total) A protocol is a complete set of rules regarding information exchange between same level layers between sites . An interface is a complete set of rules regarding information exchange between adjacent layers in a single site . d) Sketch the OSI model. Describe the purpose of each layer. 0.5 each and round-up (3 pts total) +------------------+ | Application | 7 – Provides access to applications +------------------+ | Presentation | 6 – Provides data independence +------------------+ | Session | 5 – Manages end-to-end connections +------------------+ | Transport | 4 – Provides reliable end-to-end data transfer +------------------+ | Network | 3 – Maintains point-to-point connections +------------------+ | Data link | 2 – Provides reliable error-free point-to-point data transfer +------------------+ | Physical | 1 – Transmission of bit stream (cabling, voltages, etc.) +------------------+ e) Name at least three standards organizations (in the area of communications) and briefly describe what they standardize and how they operate. 1 each (3 pts total) IETF – Internet standards (called RFCs). Entirely open, anyone welcome to come and present, everything posted on the web. Build it, standardize it. IEEE – Ethernet and WiFi standards. Mostly open, mostly anyone can present, most stuff presented on the web. ITU – Telephony standards. Closed. Invited by special permission. Only final standard is available (and at a non-trivial cost). Standardize it, build it. ISO and FCC are other possible answers.
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Problem #2 (10 minutes) Consider two hosts A and B connected by a single link of rate
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This note was uploaded on 04/24/2011 for the course CNT 4704 taught by Professor Guha,r during the Fall '08 term at University of Central Florida.

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MidtermProblems - Mid-Term Exam for Computer Networks Fall...

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