# Network

COEN 233 Computer Networks Department of Computer Engineering Santa Clara University Dr. Ming-Hwa Wang Phone: (408) 525-2564 Course website: Office Hours: Fall Quarter 2012 Email address: mwang2@engr.scu.edu http://www.cse.scu.edu/~mwang2/network/ Monday & Wednesday 9:00-9:30pm

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Due date: 7:10pm, January 14, 2013 Problem 1 What is the ISO OSI protocol stack? Please describe the functionality for each layer. ---------The answer is in your text book. Problem 2 Please give the whole names for the following acronyms: PMD, ITU-T, THF, PSTN, QAM, FTTC, SONET, AMPS, VSAT, HEC. --------- PMD: Physical Medium Dependent ITU-T: International Telecommunication Union – Telecommunication standarization section THF: Tremendously High Frequency PSTN: Public Switched Telephone Network QAM: Quadrature Amplitude Modulation FTTC: Fiber To The Curb SONET: Synchronous Optical NETwork AMPS: Advanced Mobile Phone System VSAT: Very Small Aperture Terminal HEC: Header Error Control Problem 3 Suppose that a link between two telephone offices has 50 repeaters. Suppose that the probability that a repeater fails during a year is 0.01, and that repeaters fail independently of each other. What is the probability that the link does not fail at all during one year? --------Let p be the probability that a repeater fails during a year, then 1 – p is the probability that it does not fail, and the probability that all 50 repeaters do not fail is (1 – .01)50 ≈ e–50(.01) = 0.605 where we have used the approximation (1 – p)n ≈ e–np which is valid for large n and small p.

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