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Controlling High-Bandwidth Flows at the Congested Router

Controlling High-Bandwidth Flows at the Congested Router. Ratul Mahajan, Sally Floyd, David Wetherall AT&T Center for Internet Research at ICSI (ACIRI) and AT&T Labs Research. Presented by Yan Gao. Oscillation. Paper used below method to reduce oscillation

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Controlling High-Bandwidth Flows at the Congested Router

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  1. Controlling High-Bandwidth Flows at the Congested Router Ratul Mahajan, Sally Floyd, David Wetherall AT&T Center for Internet Research at ICSI (ACIRI) and AT&T Labs Research Presented by Yan Gao

  2. Oscillation • Paper used below method to reduce oscillation • The reduction in the dropping probability is bounded by a max_decrease in one step; • The oscillation can also be caused by reaction delay and imprecision of using a flow’s packet drop history as an estimate of its arrival rate. • Changes to the dropping probability are not make until a certain time period. How to set this certain time period? • The paper did not explore the potential for oscillations in the average queue size, in particular for scenarios with large propagation delays and long-lived traffic. • In practical, the average queue size varies significantly.

  3. Mechanism • It can be only applied for non-burst packet drop behavior. • How about burst packet drop case? • Detecting unresponsive flows is tricky in variable demand environments

  4. Mechanism • Since fast memory is not required for storing the drop history, does it affect the speed of online operation? • This paper didn’t show the precise state requirements and fairness tradeoffs under various traffic scenarios. • RED-PD’s test for unresponsiveness can have false positives and false negatives. • What are the results of their evaluation?

  5. Parameter setting • Changes in the network might expose the importance of different parameters. • The parameters have proved important in the past, so it should provide observations of their values on the Internet, and describe expected effects of other values. • How could they set these parameters? Do they have some recommendation for different network? (such as K, M)

  6. Evaluation • The authors only did some very small level simulation by NS-2 (10Mbps), how about the behavior on large scale network (such as 10Gbps) ??? • The paper did not investigate performance for a range of link bandwidths for the congested link. • Whether the approach will reduce totally bandwidth waste is still unknown. • Bandwidth is wasted by delivering packets through the network that are dropped before reaching their ultimate destination; • There is no good way for responding to unresponsive flows.

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