Paper review: General AMID Congestion Control

Reviewer: Kevin Hofstra

1. What is the best algorithm for congestion avoidance? Should all protocols, such as UDP and other best effort, time sensitive also be forced to abide by congestion parameters? Can flow parameters be altered to allow different sending rates?
2. An evaluation of the different congestion control algorithms, and an attempt to make improvements on their efficiency, fairness, and convergence speed. Investigation into how parameters effect sending rates. An analysis of the GAIMD as TCP-Friendly.
1. The most effective algorithm is GAIMD, which changes window size by a multiplicative factor during a triple-duplicate ACK, changes it to 1 if there is a timeout, and uses an additive increase if it is successful.
2. The relationship between alpha and beta for GAIMD is shown to be TCP-Friendly. The flow rate of GAIMD flows have approximately the same sending rate as a TCP flow under the same conditions.
3. The backoff reduction of 7/8 decreases the rate fluctuation, and conversion speed when compared with the old value of ½. By reducing the deviation from the optimum flow rate, the convergence speed to maximum efficiency is increased at a slight cost of larger packet lost in very high congestion.
4. You can control flow parameters so that flows with different values can achieve different sending rates.
4. Critique the main contribution
• Significance- 3 The article is very effective in showing how different algorithms for congestion avoidance will reduce lost packets, responsiveness, and convergence, but is more an investigation of how to alter existing solutions to be more effective.
• Convincing- 4 The data gathered supports their proposed solutions. They are able to show that by controlling flow parameters they are able to achieve varying sending rates. The GAIMD flow rate is demonstrated to be TCP-Friendly, which is one of their major successes in a heterogeneous environment.
5. System researchers and builders should recognize that the major point in the success of GAIMD is the fact that it has been proved TCP-Friendly. Therefore it will not throw off the balance that TCP congestion control is establishing. The fact that is is true while modifying the parameters of backoff allows GAIMD to be fine tuned for best performance. We have reduced the backoff in attempt to increase efficiency and reduce conversion time, and the paper shows us that this is possible without sacrificing congestion avoidance stability.