R2 (user 2) Consider TCP fairness scenario as shown in the slide #2 in Transport chapter, which illustrates the convergence of TCP’s AIMD algorithm. There are two connections through the same bottleneck link of capacity R to the same server, as depicted in the figure in slide #2. Suppose that instead of a multiplicative decrease, TCP decreases the window size by a constant amount as follows: equal bandwidth share (y = x) (a) Both connections decrease their window size by -1 instead of multiplicative decrease. Would the resulting AIAD algorithm converge to an equal share? What are the long-term throughput of these two connections? Justify your answer by showing how the throughput of two connections (users) evolve over time, assuming that they start from the point ‘A’ in Figure 3 with short explanation on the plot you draw. (b) Now, connection 1 decreases its window size by -3 while connection 2 decreases only by -1. All other parts remain the same as above. Would this version of AIAD algorithm (but two connections behave differently) converge to an equal share? What are the long-term throughput of these two connections? Justify your answer by showing how the throughput of two connections (users) evolve over time, assuming that they start from the point ‘A’ in Figure 3 with short explanation on the plot you draw. R R1 (user 1) Figure 3: Effect of TCP modification #2 AIMD TCP Fairness Fairness goal: If N TCP sessions share same bottleneck link, each should get 1/N of link capacity TCP congestion avoidance: AIMD: additive increase, multiplicative decrease ► Increase window by 1 per RTT ► Decrease window by factor of 2 on loss event TCP connection 1 bottleneck TCP connection 2 router capacity R Show transcribed image text R2 (user 2) Consider TCP fairness scenario as shown in the slide #2 in Transport chapter, which illustrates the convergence of TCP’s AIMD algorithm. There are two connections through the same bottleneck link of capacity R to the same server, as depicted in the figure in slide #2. Suppose that instead of a multiplicative decrease, TCP decreases the window size by a constant amount as follows: equal bandwidth share (y = x) (a) Both connections decrease their window size by -1 instead of multiplicative decrease. Would the resulting AIAD algorithm converge to an equal share? What are the long-term throughput of these two connections? Justify your answer by showing how the throughput of two connections (users) evolve over time, assuming that they start from the point ‘A’ in Figure 3 with short explanation on the plot you draw. (b) Now, connection 1 decreases its window size by -3 while connection 2 decreases only by -1. All other parts remain the same as above. Would this version of AIAD algorithm (but two connections behave differently) converge to an equal share? What are the long-term throughput of these two connections? Justify your answer by showing how the throughput of two connections (users) evolve over time, assuming that they start from the point ‘A’ in Figure 3 with short explanation on the plot you draw. R R1 (user 1) Figure 3: Effect of TCP modification #2 AIMD TCP Fairness Fairness goal: If N TCP sessions share same bottleneck link, each should get 1/N of link capacity TCP congestion avoidance: AIMD: additive increase, multiplicative decrease ► Increase window by 1 per RTT ► Decrease window by factor of 2 on loss event TCP connection 1 bottleneck TCP connection 2 router capacity R
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