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Pagina 1 di 9 Fundamentals of Communication Networks Prof. G. Maier Exam – 14th February 2018 Surname Name Student ID Total time 2:00 Ex1 (7pt) Ex2 (6pt) Ex3 (6pt) Ex4 (5 pt) Ques (8 pt) 1 - Exercise (7 points) Consider the network below, where links are coaxial cables. At time t=0, host A starts sending a sequence of 5 packets (one immediately after the other) with the following destinations: E, B, B, D, B. Exactly at the time tD=40 µs, host D starts sending a sequence of 2 packets (one immediately after the other) with the following destinations: C, C. All the packets have equal length, and each comprises a header of h=2 byte and a payload of p=28 byte. All the nodes operate in the store-and-forward mode. With the help of time diagrams, compute the arrival time of each packet to destination. [Remind that the speed of light in a guided media can be given in the form 5 µs/km] Pagina 2 di 9 Pagina 3 di 9 2 - Exercise (6 points) Look at the switched-Ethernet network in the first figure below (the thick lines represent broadcast network segments). Initially (t=0) all the MAC tables of the switches are empty. The sequence of frames generated by the stations in the subsequent instants is reported in the first column of the table (listing, for each frame, source and destination MAC address). Fill-in the other columns by writing at each time and for each switch the new entry of the MAC table (if any) that is leaned by the switch by the learning-and-forwarding mechanism. Write each entry in the form: MAC address – port number (see the example). If the new entry is already present in the MAC table, write it in parentheses (…). At time t=7T, the topology of the network is rearranged by changing the positions of stations A, G and H as shown in the secon d figure. Fill-in the…