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Pagina 1 di 9 Fundamentals of Communication Networks Prof. G. Maier Exam – 18 January 2019 Surname Name Student ID Total time 2:20 Ex1 (7 pt) Ex2 (5 pt) Ex3 (5 pt) Ex4 (7 pt) Ques (8 pt) 1 - Exercise (7 points) In the network below, host A establishes a TCP connection with host B. The two hosts are connected by a satellite link. The satellite (Medium Earth Orbiting – MEO), is at an approximate distance of d = 30000 km from the Earth. Transmission from ground stations towards the satellite occurs at a speed Cup = 2 Mbit/s, while the satellite transmits towards the ground stations at a speed Cdown = 4 Mbit/s. The satellite operates as a store-and-forward intermediate node. Assuming • Header and ACK lengths negligible • MSS = 10 kbyte • RCWND = 100 kbyte for the whole duration of the connection • SSTHRESH = 80 kbyte 1- Compute the length Wc of the window that allows continuous transmission. 2- Compute the time needed to transfer a file of length B = 540 kbyte from A to B (from TCP connection setup to reception of the last ACK packet). 3- Repeat the computation by assuming that all the segments of the second window got lost and the timeout is Tout=2 RTT (counted starting at the beginning of segment transmission) Make use of a time diagram to visualize the solution. Pagina 2 di 9 Pagina 3 di 9 2 - Exercise (5 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…