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Fundamentals of Communication Networks Prof. G. Maier Exam – 9th July 2018 Surname Name Student ID Total time 2:15 Ex1 (6pt) Ex2 (6pt) Ex3 (6pt) Ex4 (6 pt) Ques (8 pt) 1 - Exercise (7 points) An orbiting module B of a lunar exploration mission is orbiting around the Earth at a distance of d = 1.2 light- seconds from the terrestrial surface. The mission control room on the Earth A transfers a block of data to B using an ARQ protocol. Assume that during the transfer time A and B are mutually still. The transmission speeds are the following: link A  B: Cu = 1.2 kbit/s link B  A: Cd = 320 bit/s The features of the ARQ protocol are the following: fixed size of the ACK frames: La = 8 byte, maximum size of the data frames: Lfmax = 60 byte, of which 8 byte are the frame overhead processing time at stations A and B negligible The data block to be sent has size B = 328 byte, and all the data frames have maximum length, possibly except the last one. If the ARQ protocol is of stop-and-wait type and transmission occurs with no errors, compute: the transfer time TS&W of the data block (from the beginning of the transmission of the first frame to the reception of the last ACK);1) the data-connection effective throughput THRS&W, = B / TS&W, measured in [bit/s], and how much this is in percentage compared to the capacity of the channel A  B (efficiency S&W). 2) Now consider that the ARQ protocol is of type go-back-n, with transmission window of size Wt =4f r a m e s . Compute (with no errors): the values of the parameters requested in 1) and 2) with the GBN;1) the size of the transmission window Ws-ott-gbn that would maximize the throughput with the GBN;2) Graphically represent the two cases of frame transfer using time diagrams. FCN ‐ 09_07_18 lunedì 16 luglio 2018 12:53 FNC…