CS/CE 6390 Advanced Computer Networks Prof. Zygmunt J. Haas Spring 2015 Homework # 3: Chapter 5 (End-to-End Protocols) Rules: 1. Due Wednesday, March 4, 2015 at 11:30am, in class 2. Solve all the 11 problems below for 100 points - independent work only. 3. Show full solution to the problems - do not skip steps. Solve the following problems (in the textbook, starting on page 469): 1. 2. 3. 4. 5. Problem 26 Problem 28 Problem 30 Problem 31 Problem 51 Solve the following problems 6. If the TCP round-trip time, RTT, is currently 30 msec and the following acknowledgements come in after 26, 32, 24, msec, respectively, what is the new RTT estimate? (Assume that the parameter of the filter is α=0.9. 7. A TCP is sending packets over a 1 Gbps connection that has a one-way delay of 10 msec. a. What should be the minimum window size (in packets) for the channel utilization to be greater than 80% ? Assume packet size of 1000 Bytes. b. If the window size is 65,536 bytes:  What is the maximum achievable throughput?  What is the connection efficiency? 8. In a network with a maximum Protocol Data Unit (PDU) of 128 bytes, a maximum PDU lifetime of 30 seconds and an 8-bit sequence number, what is the maximum data rate per connection? Assume that the protocol uses Selective Repeat. 9. You are designing a reliable, sliding window, byte-stream protocol similar to TCP. It will be used for communication with a geosynchronous satellite network, for which the bandwidth is 1 Gbps and the RTT is 275 ms. Assume the maximum segment lifetime is 30 seconds. a. How many bits wide should you make the AdvertisedWindow and SequenceNum fields? b. If AdvertisedWindow is 16 bits, what upper bound would that impose on the effective bandwidth? c. If it turns out that 0.5% of the packets sent over the path are lost, what throughput would you expect a long-running TCP connection to achieve? (Assume AdvertisedWindow as in part b and TimeOut = 4RTT. 10. Suppose that the five measured SampleRTT values are 106ms, 120ms, 140ms, 90ms, and 115ms. a. Compute the EstimatedRTT after each of these SampleRTT values is obtained, using a value of α = 0.125 and assuming that the value of EstimatedRTT was 100ms just before the first of these 5 samples were obtained. b. Compute the DevRTT after each sample is obtained, assuming a value of  = 0.25 and assuming the value of DevRTT was 5ms just before the first of these five samples was obtained. c. Compute the TCP TimeOut after each of these samples is obtained, assuming =1 and =4. See next page for problem 11 Copyright  by Zygmunt J. Haas, 2015 1 11. Find the MST and its cost for the following network using (a) Krusal’s and (b) Prim’s algorithms: 12 A H 4 7 10 G 18 8 16 F 9 17 B I 6 5 14 3 E 19 11 13 15 20 D C Copyright  by Zygmunt J. Haas, 2015 2