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Does TCP New Congestion Window Validation Improve HTTP Adaptive Streaming Performance?

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Proceedings of the Workshop on Network and Operating System Support for Digital Audio and Video (NOSSDAV), June .

DOI:10.1145/3534088.3534347

This Work has been Retracted by ACM at the request of the authors. The authors notified ACM that they found a bug in their experiments. This bug caused the control case, TCP New Reno without the new congestion window validation algorithm, to incorrectly reset its slow-start threshold after an idle period. The resulting code was inconsistent with both the TCP specification and the standard Linux TCP implementation and would overshoot the intended sending rate causing a burst of packet loss. The results for the algorithm under test, TCP with new congestion window validation, were correct, but did not provide the benefits claimed compared to the corrected control.

When using HTTP adaptive streaming, video traffic exhibits on-off behaviour with frequent idle periods that can interact poorly with TCP congestion control algorithms. New congestion window validation (New CWV) modifies TCP to allow senders to recover their sending rate more quickly after certain idle periods. While previous work has shown that New CWV can improve transport performance for streaming video, it has not been shown if this translates to improved application performance in terms of playback stability. In this paper, we show that New CWV can reduce video re-buffering events by up to 4%, and limit representation switches by 12%, without any changes to existing rate adaptation algorithms.

Download: yanev2022newcwv.pdf