Question

1. For TCP end-to-end flow control, suppose the capacity of the receiver buffer is 10 packets. Suppose the packets that are being queued in the receiver buffer are packets 4, 5, 6, 7, 8, 10, 11. What is the advertised window size the receiver sent to the sender? Suppose packet 12 is the last packet sent by the sender. What’s the effective window size at the sender? Can the sender send out packet 13 at this moment? How about packet 14?

2. Consider a TCP Tahoe flow. Assume the initial TCP congestion window size is cwnd=1 packet, ssthreshold=10 packet, and the sender sends out packets starting from packet 1. Suppose packet 5 is lost in its first transmission and will go through in subsequent try. All other packets will go through in their first transmission. Plot the time line graph for this flow until the transmission of packet 15. You also need to show the value of cwnd and ssthreshold in your time line figure. In your calculation, ignore the impact from awnd (i.e., we assume awnd is sufficiently large) and assume TCP timeout is three times the RTT.

3. Draw the routing table for the following nodes A, B, C, and D such that A to B = 5, B to C = 1, A to C = 1, and C to D = 1 topology when distance vector routing algorithm is used. You need to draw the table for every node and for every round of their information exchange until it converges.

4. Use Dijkstra’s algorithm to decide the shortest path from node A to every other nodes in the following topology. You must plot every step of the execution of the algorithm. The topology is AB=6, AC=3, AD=3, BD=2, BE=2, CD=5, CE=2, DF=3, and EF=1.

5. What is the time line figure for a TCP Reno flow, given that all the other conditions are the same as in question 4? You also need to show the value of cwnd and ssthreshold in your figure.

3 4

Answer 1

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