EE122 Communication NetworksHomework Assignment 2Prof. Ion Stoica and Dr. Kevin LaiDue Date: Monday, October 7, 15:50Name:SID:EE122 login:Discussion Section:Problem Points123456TotalEE122 Communication NetworksHomework Assignment 2Prof. Ion Stoica and Dr. Kevin LaiSeptemb er 23, 2002Due Date: Monday, October 7, 15:501. (2.151) Suppose we want to transmit the message 11001001 and protect itfrom errors using the CRC polynomial x3+ 1.(a) Use polynomial long division to determine the message that shouldbe transmitted.(b) Suppose the leftmost bit of the message is inverted due to noise onthe transmission link. What is the result of the receiver’s CRC cal-culation? How does the receiver know that an error has o ccurred?2. (2.36) Suppose the round-trip propagation delay for Ethernet is 46.4 µs.This yields a minimum packet size of 512 bits (464 bits corresponding topropagation delay + 48 bits of jam signal).(a) What happens to the minimum packet size if the delay time is heldconstant, and the signaling rate rises to 100 Mbps?(b) What are the drawbacks to so large a minimum packet size?(c) If compatibility were not an issue, how might the specifications bewritten so as to permit a smaller minimum packet size?3. (3.1) Using the example network given in Figure 1, give the virtual circuittables for all the switches after each of the following connections is estab-lished. Assume that the sequence of connections is cumulative; that is,the first connection is still up when the second connection is established,and so on. Also assume that the VCI assignment always picks the lowestunused VCI on each link, starting with 0.(a) Host A connects to host B.(b) Host C connects to host G.1This indicates that it is Problem 15 in Chapter 2 in Peterson and Davie’s book. The lefthas the same meaning.13021Switch 1023 101230123Switch 3Switch 4Switch 2Host DHost AHost EHost JHost CHost FHost GHost HHost BHost IFigure 1: Example network for Problem 3.(c) Host E connects to host I.(d) Host D connects to host B.(e) Host F connects to host J.(f) Host H connects to host A.4. (4.12 and 4.15) Consider the network given in Figure 2.A2CFBED82316Figure 2: Example network for Problem 4.(a) Give the global distance-vector tables2when2Refer to Tables 4.5 and 4.8 in Pages 285 and 286 in Peterson and Davie’s book.2i. Each node knows only the distances to its immediate neighbors.ii. Each node has reported the information it had in the precedingstep to its immediate neighbors.iii. The second step above happens a second time.(b) Show how the link-state algorithm builds the routing table for nodeD3.5. (4.15) For the network in Figure 2, suppose the forwarding tables are allestablished as in Problem 4.(a) and then the C − E link fails. Give(a) the tables of A, B, D, and F after C and E have reported the news(b) the tables of A and D after their next mutual exchange(c) the table of C after A exchanges with it6. What are the differences between a distance-vector and a link-state routingprotocol? Enumerate at least two of them.3Refer to Table 4.9 in Page 297 in Peterson and Davie’s
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