Exercise 5.4.
Show the pseudoheader and the TCP segment with source socket <10.0.0.1,8191>, destination socket <192.168.255.17,1539>, SN = 17,000, AN = 152, window = 1000, payload “Dante” and all other fields set at zero, which are used for the checksum calculation, also determining the decimal value obtained.

Exercise 5.7.
Consider a TCP connection that adopts the default MSS value and MSL = 2 min. Determine the maximum capacity C of an IP stream that supports the TCP connection, so that two bytes with the same number can never be found in the network assuming that the IP datagrams have a header of 20 bytes.

Exercise 5.9.
Consider the transfer of data between two stations, A and B, through a TCP connection with the following hypotheses: (i) only station A receives data to be sent from its application and in particular a first block of 4500 bytes at time t = 0 and a second block of 4000 bytes at time , where the transmission time Ts of a segment with maximum size MSS = 1500 byte is given by and is the propagation delay between the two stations; (ii) the second segment sent by station A is not received by station B; (iii) the transmission time of an acknowledgment is ; (iv) the initial numbering is = 1000 and = 500. Determine for this case the value of the time-out beyond which the fast retransmit procedure allows the lost segment to be retransmitted faster.

Exercise 5.13.
Consider the algorithm for estimating the round trip time (RTT) used by the TCP protocol. Calculate the new RTT value if the current estimate is RTT = 15 ms and 5 acknowledgments are received which result in the measured RTT delays equal to 18, 23, 24, 32 ms. Assume the suggested values for the weight coefficients.

Exercise 5.16.
Two hosts are connected through a network that makes a radio link of length d = 80 km and of constant capacity C = 80 Mbit/s available. The TCP transport protocol is used to transfer segments from host A to host B, all with fixed size MSS = 1000 bytes, with the initial congestion window opening Cwnd = 1 MSS for the two values of the threshold = 32 MSS and = 4 MSS, starting transmission of the first segment at time t = 0. Assuming that no errors occur during data transfer and that the length of the acknowledgment messages is negligible, evaluate the time T required to complete the transfer of a file with 27.5 kbytes from A to B for each of the two values and .

Exercise 5.21.
Represent the evolution of the congestion window opening for the TCP Tahoe and TCP Reno protocols for the first 40 RTT intervals in the hypothesis that: (i) one of the segments sent at time 13 RTT is lost and only duplicate acknowledgments are received; (ii) the network is faulty in the interval (14-15) RTT and no segments are transmitted; (iii) the network goes out of service in the interval (23-25) RTT. The initial values are: threshold Ssthresh = 16 MSS between the two regions, congestion window Cwnd = 1 MSS, timeout = 2 RTT. Transmission begins at time 1 RTT.