Assignment 3 – Transport Layer 1. Computing an Internet checksum. (25 points) Consider the two 16-bit words (shown in binary) below. Recall that to compute the Internet checksum of a set of 16-bit...

Please read the files attach below so we can get this done ASAP.


Assignment 3 – Transport Layer 1. Computing an Internet checksum. (25 points) Consider the two 16-bit words (shown in binary) below. Recall that to compute the Internet checksum of a set of 16-bit words, we compute the one's complement sum [http://mathforum.org/library/drmath/view/54379.html] of the two words. That is, we add the two numbers together, making sure that any carry into the 17th bit of this initial sum is added back into the 1's place of the resulting sum); we then take the one's complement of the result. o Compute the Internet checksum value for these two 16-bit words: o With the checksum value (1’s complement) how does receiver detect errors? 00100000 10010001 this binary number is 8337 decimal (base 10) 11101010 11010010 this binary number is 60114 decimal (base 10) 2. TCP sequence and ACK numbers with segment loss. (25 points) Consider the figure below in which TCP a sender and receiver communicate over a connection in which the sender-to-receiver segments may be lost. The TCP sender sends initial window of five segments at t=1,2,3,4,5, respectively. Suppose the initial value of the sender-to-receiver sequence number is 123 and the first five segments each contain 513 bytes. The delay between the sender and the receiver is 7 time units, and so the first segment arrives at the receiver at t=8. As shown in the figure, two of the five segment(s) are lost between the sender and the receiver. Answer the following questions (Fill in the following table): a. Give the sequence numbers associated with each of the five segments sent by the sender b. List the sequence of acknowledgements transmitted by the TCP receiver in response to the receipt of the segments actually received. In particular, give the value in the http://mathforum.org/library/drmath/view/54379.html acknowledgement field of each receiver-to-sender acknowledgement, and give a brief explanation as to why that particular acknowledgement number value is being used Sender-to- Receiver Time segment sent Sender-to-receiver segment sequence number field value Time segment received, and ACK segment sent Receiver-to- sender ACK field value Segment 1 1 Segment 2 2 Segment 3 3 N/A Segment 4 4 N/A Segment 5 5 3. Computing TCP's RTT and timeout values. (25 points) Review Chapter_3-3 for more information Suppose that TCP's current estimated values for the round trip time (estimatedRTT) and deviation in the RTT (DevRTT) are 350 msec and 45 msec, respectively (see Section 3.5.3 for a discussion of these variables). Suppose that the next three measured values of the RTT are 350, 290, and 380 respectively. Compute TCP's new value of estimatedRTT, DevRTT, and the TCP timeout value after each of these three measured RTT values is obtained.Use the values of α = 0.125 and β = 0.25. 4. TCP in action: slow start, congestion avoidance, and fast retransmit. (25 points) Fill in the following graph showing the congestion window size for TCP Reno and TCP Tahoe assuming that the initial ss-threshold is 8 and that a loss event will occur when the window size is 14. Recall from Chapter_3-4 for TCP Reno and TCP Tahoe. When filling in the graph mark o (circle) for slow start, mark * (asterisk) congestion avoidance, mark + (plus) for fast recovery.