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Week 5 Tut Work
Networking Fundamentals (41092)
University of Technology Sydney
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41092 Network Fundamentals
Week 5. Tutorial Problems
P1. Suppose Client A requests a web page from Server S through HTTP and its socket is associated with port 33000. a. What are the source and destination ports for the segments sent from A to S? b. What are the source and destination ports for the segments sent from S to A? c. Can Client A contact to Server S using UDP as the transport protocol? d. Can Client A request multiple resources in a single TCP connection?
P2. Consider Figure 3. a. Let us assume the following change: at B we want to access an FTP server from host A. What port number should be used to replace port 80? b. Would there be an error if the right process of C used port number 8080? c. What are the source and destination network and port values in the segments flowing from the server back to the clients’ processes?
P3. UDP and TCP use 1s complement for their checksums. Suppose you have the following three 16 bit words: 0101001101100110; 0111010010110100; 0000110111000001. What is the 1s complement of the sum of these words? Show all work. Why is it that UDP offers a checksum? With the 1’s comple-ment scheme, how does the receiver detect errors? Describe how a single bit flip can be detected.
P4. Assume that a host receives a UDP segment with 01011101 11110010 (we separated the values of each byte with a space for clarity) as the checksum. The host adds the 16-bit words over all necessary fields excluding the check-sum and obtains the value 00110010 00001101. Is the segment considered correctly received or not? What does the receiver do?
P5. Suppose that the UDP receiver computes the Internet checksum for the received UDP segment and finds that it matches the value carried in the checksum field. Can the receiver be absolutely certain that no bit errors have occurred? Explain.
P9. Give a trace of the operation of protocol rdt3 when data packets and acknowledgment packets are garbled. Your trace should be similar to that used in Figure 3.
P15 You are transmitting huge amount of data across a link of rate 100Mbps, over a distance of 1100km. The packet size is 1200Byte, and the propagation speed is 2^8 m/s. Assuming perfect channel with no packet error or loss. a. If rdt3, stop-and-wait, protocol is used, what is the link utilization? Note. use two significant figures in your results. b. If pipelining protocol is used with a window size of 5 packets, what is the link utilization? What is the link throughput? Note. use two significant figures in your results. c. (optional research question – not tested) What is the minimum window size in order to achieve full utilization? What is the link throughput in this case?
Kurose & Keith, Computer Networking: A Top-Down Approach, 8th Edition. Pearson
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Week 5 Tut Work
Course: Networking Fundamentals (41092)
University: University of Technology Sydney
