20190716sol

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1 - Exercise (7 points) Consider the two alternative fixed-wireless systems represented in the figure, connecting two stations A and B located on the top of two mountains. The system at the bottom is a direct link, while the system on the top has an intermediate station X located exactly halfway that retransmits frames (operating in store- and-forward mode). The distance between A and B is d = 30 km. All transmitters operate at bitrate C = 320 Mbit/s. All data frames have length L =1k b yte, with negligible headers. ACKs are transmitted on frames of negligible length. A data block of size F = 7 kbyte is transferred from A to B (only ACKs are sent in the opposite direction). In both systems, frames are transmitted using an ARQ go-back-n protocol, with the following features: In the single-link case, GBN-ARQ is active between A and B, with the minimum window size W that potentially allows continuous transmission  In the two-link case, there is a GBN-ARQ protocol active between A and X and another GBN-ARQ protocol between X and B. On both links, the window size is W’ =4 f r a m e s. [hint: note that, as a consequence of the GBN-ARQ protocol, X will not retransmit frames arrived in X out-of-sequence.  For both the systems: In absence of transmission errors, draw the time diagram and compute the transfer time TGBN of the data block (from the beginning of the transmission of the first frame from A to the end of reception of the last frame in B); 1) Repeat 1) in case the second frame gets lost during the transmission between A and B (in the single-link case) and between A and X (in the two-link case). 2) 16/07/2019 lunedì 22 luglio 2019 18:50 FCN 2018-19 Pagina 1 2 - Exercise (6 points) A router has the following interface configuration and routing table: Eth0:…