ex2_1sol - Mid-Term Exam for Computer Networks Fall 2010 >...

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Mid-Term Exam for Computer Networks Fall 2010 >>> SOLUTIONS <<< Welcome to the Mid-Term Exam for Computer Networks . Read each problem carefully. There are eight required problems (each worth 12 points – you get 4 points for correctly following these instructions). There is also an additional extra credit question worth 10 points. You may have with you a calculator, pencils and/or pens, 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 in pencil or ink on both sides of the sheet. Photocopies, scans, or computer generated and/or printed text are not allowed on this sheet. Note to tablet PC users – you may not print-out your handwritten text for the formula sheet. You have 75 minutes for the exam. Please use a separate sheet of paper for the answer to each question . Good luck and be sure to show your work! Problem #1 Answer the following questions regarding the basics of computer networks and the Internet. a) What are the basics tasks of a communications system? 0.25 each and round-up (2 pts total) Message formatting, error detection and recovery, addressing, routing, flow control, system management, security, and QoS b) What are the fundamental challenges to improve communications systems (hint: think about the fundamental measures of a communications system)? 0.25 each and round-up (2 pts total) Greater throughput, less delay, less loss, lower cost, more mobility, greater robustness, and better secrecy c) Think about the OSI reference model and the 5-layer Internet reference model we are using in this class. Identify what is different between these two models (be more specific than just saying “two layers”!). 1 each layer noted (2 pts total) The key difference is that the 5-layer Internet model does not have the presentation and session layers found in the OSI model. Otherwise the models are essentially the same . d) In the 5-layer Internet reference model which layers handle point-to-point functions and which layers handle end-to-end functions? 0.5 each and round-up (2 pts total) Note: Will accept layer 3 as point-to-point Layers 1 and 2 are point-to-point and layers 3 and 4 are end-to-end. e) Is sockets a protocol or interface? Carefully explain why. 1 each for key point (2 pts total) An interface is a complete set of rules for information exchange between adjacent layers in a single site – and this is the function that sockets provides as an applications programming interface (API) where the underlying protocol is TCP or UDP. So, sockets is an interface. f) What problems do Information Theory and Coding Theory address? In what department are these areas typically studied. 1 each (2 pts total)
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This note was uploaded on 01/09/2012 for the course CS cs464 at Bilkent University.

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ex2_1sol - Mid-Term Exam for Computer Networks Fall 2010 >...

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