Re: TCP connection issues against Amazon S3

From: Rick Jones
Date: Thu Jan 08 2015 - 13:53:07 EST



Strange thing is that sender does not misbehave at the beginning when
receiver window is still small. Only after a while.

Just guessing, but when the receiver window is small, the sender cannot get a large quantity of data out there at once, so any string of lost packets will tend to be smaller. If the sender is relying on the RTO to trigger the retransmits, and is not resetting his RTO until the clean ACK of a segment sent after snd_nxt when the loss is detected, the smaller loss strings will not get to the rather large RTO values seen in the trace before curl gives-up. It may be that the sender is indeed misbehaving at the beginning, just that it isn't noticeable?

Different but perhaps related observation/question - without timestamps (which we don't have in this case), isn't there a certain ambiguity about arriving out-of-order segments? One doesn't really know if they are out-of-order because the network is re-ordering, or because they are retransmissions of segments we've not yet seen at the receiver.

rick
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