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Pagina 1 di 10 Fundamentals of Communication Networks Prof. G. Maier Exam – 18 February 2018 Surname Name Student ID Total time 2:00 Ex1 (7pt) Ex2 (6pt) Ex3 (5pt) Ex4 (6pt) Ques (8pt) 1 - Exercise (7 points) Consider the network below. All the physical links are bidirectional symmetric twisted-pair links. The following two TCP connections are always active all the time: i) C-B, along the path C-R1-R3- R2-B; ii) E-D, along the path E-R3-R2-D. At time t=0, two HTTP sessions are opened in parallel between the client A and the server B, to download two documents of lengths LOBJ-1 = 40 kbyte and LOBJ-2 = 60 kbyte, respectively. Both connections are routed along the path A-R1-R3-R2-B. Apply the fair-sharing model to compute the average rates for each connection. Then compute the times at which the two objects are completely arrived at the client. Assume that control segments exchanged in the hand-shaking phase, as well as the GET message, have negligible length. Make use of the time diagrams to visualize the object acquisition. Repeat the exercise assuming that the connection used to transfer OBJ-1 is routed along the path A- R1-R2-B, while the connection used to transfer OBJ-2 is still routed along the path A-R1-R3-R2-B. Pagina 2 di 10 Pagina 3 di 10 2 - Exercise (6 points) An ISP owns the following IP addressing space : 131.47.128.0 netmask 255.255.128.0. The ISP network is shown in the picture below. The ISP has two networks for large customers, A and B, having about 7000 hosts each. Other two networks, C and D, are assigned to medium customers, the first asking connectivity for 2050 hosts, and the second for 3500 hosts. Network E with 1000 hosts is us ed by the ISP itself for management functions. Finally, pp1 to pp5 are point-to-point links to connect the routers.…