ex2_2_sol_fall09

ex2_2_sol_fall09 - Final Exam for Computer Networks Fall...

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Final Exam for Computer Networks Fall 2009 >>> SOLUTIONS <<< Welcome to the Final Exam for Computer Networks . Read each problem carefully. There are ten required problems (each problem is worth 10 points). 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 120 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 on the basics of computer networks and the Internet. a) Sketch the OSI model and briefly describe the function of each layer 0.5 each (4 pts total rounded up) +------------------+ | 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.) +------------------+ b) Name the four factors of delay for a packet. Then, identify which factor will most likely predominate (i.e., be the largest factor) for 1000 Byte packets in a flow on a 1) 10 Mb/s LAN segment between two PCs in the same building, 2) 1 Mb/s geosynchronous-orbit satellite link between the US and Nepal, 3) on the Internet between the US and Nepal. 1 pt each identified largest factor (3 pts total) The four factors of packet delay are processing, transmission, propagation, and queueing. For (1) the predominant delay will be transmission in the 1 ms range (processing is microseconds, propagation is nanoseconds, and queueing in non-existent), For (2) the propagation will be the largest delay (in the 100s of milliseconds), and for (3) the largest delay will likely be queueing due to the many hops between the US and Nepal. c) This class has (correctly) been called a “jargon class”. Spell-out the following acronyms and identify which layer(s) (in the 5-layer protocol model used in the book) they belong to – TCP, OSPF, IP, SNMP, MAC, and SMTP. 0.5 pt each per acronym (3 pts total rounded-up) – no points off for missing OSPF
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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_2_sol_fall09 - Final Exam for Computer Networks Fall...

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