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Yuchung Cheng authored
This patch removes the (partial) implementation of the aggressive limited transmit in RFC4653 TCP Non-Congestion Robustness (NCR). NCR is a mitigation to the problem created by the dynamic DUPACK threshold. With the current adaptive DUPACK threshold (tp->reordering) could cause timeouts by preventing fast recovery. For example, if the last packet of a cwnd burst was reordered, the threshold will be set to the size of cwnd. But if next application burst is smaller than threshold and has drops instead of reorderings, the sender would not trigger fast recovery but instead resorts to a timeout recovery. NCR mitigates this issue by checking the number of DUPACKs against the current flight size additionally. The techniqueue is similar to the early retransmit RFC. With RACK loss detection, this mitigation is not needed, because RACK does not use DUPACK threshold to detect losses. RACK arms a reordering timer to fire at most a quarter RTT later to start fast recovery. Signed-off-by:
Yuchung Cheng <ycheng@google.com> Signed-off-by:
Neal Cardwell <ncardwell@google.com> Acked-by:
Eric Dumazet <edumazet@google.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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