From: Florian Westphal <[email protected]>
Date: Tue, 6 Dec 2016 00:23:00 +0100
> Neal Cardwell says:
> If I am reading the code correctly, then I would have two concerns:
> 1) Has that been tested? That seems like an extremely dramatic
> decrease in cwnd. For example, if the cwnd is 80, and there are 40
> ACKs, and half the ACKs are ECE marked, then my back-of-the-envelope
> calculations seem to suggest that after just 11 ACKs the cwnd would be
> down to a minimal value of 2 [..]
> 2) That seems to contradict another passage in the draft [..] where it
> sazs:
> Just as specified in [RFC3168], DCTCP does not react to congestion
> indications more than once for every window of data.
>
> Neal is right. Fortunately we don't have to complicate this by testing
> vs. current rtt estimate, we can just revert the patch.
>
> Normal stack already handles this for us: receiving ACKs with ECE
> set causes a call to tcp_enter_cwr(), from there on the ssthresh gets
> adjusted and prr will take care of cwnd adjustment.
>
> Fixes: 4780566784b396 ("dctcp: update cwnd on congestion event")
> Cc: Neal Cardwell <[email protected]>
> Signed-off-by: Florian Westphal <[email protected]>
Applied.
