linux-kernel - Re: TCP connection issues against Amazon S3

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Date:	Tue, 06 Jan 2015 12:13:36 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Erik Grinaker <erik@...gler.no>
Cc:	Yuchung Cheng <ycheng@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: TCP connection issues against Amazon S3

On Tue, 2015-01-06 at 19:42 +0000, Erik Grinaker wrote:

> The transfer on the functioning Netherlands server does indeed use SACKs, while the Norway servers do not.
> 
> For what it’s worth, I have made stripped down pcaps for a single failing transfer as well as a single functioning transfer in the Netherlands:
> 
> http://abstrakt.bengler.no/tcp-issues-s3-failure.pcap.bz2
> http://abstrakt.bengler.no/tcp-issues-s3-success-netherlands.pcap.bz2
> 

Although sender seems to be reluctant to retransmit, this 'failure' is
caused by receiver closing the connection too soon.

Are you sure you do not ask curl to setup a very small completion
timer ?

12:41:00.738336 IP 54.231.132.98.80 > 195.159.221.106.48837: Flags [.], seq 767221:768681, ack 154, win 127, length 1460
12:41:00.738346 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [.], ack 736561, win 1877, length 0
12:41:05.227150 IP 54.231.132.98.80 > 195.159.221.106.48837: Flags [.], seq 736561:738021, ack 154, win 127, length 1460
12:41:05.227250 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [.], ack 745321, win 1882, length 0
12:41:05.278287 IP 54.231.132.98.80 > 195.159.221.106.48837: Flags [.], seq 768681:770141, ack 154, win 127, length 1460
12:41:05.278354 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [.], ack 745321, win 1888, length 0
12:41:05.278421 IP 54.231.132.98.80 > 195.159.221.106.48837: Flags [.], seq 770141:771601, ack 154, win 127, length 1460
12:41:05.278429 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [.], ack 745321, win 1894, length 0
12:41:14.257102 IP 54.231.132.98.80 > 195.159.221.106.48837: Flags [.], seq 745321:746781, ack 154, win 127, length 1460
12:41:14.257154 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [.], ack 746781, win 1900, length 0
12:41:14.308117 IP 54.231.132.98.80 > 195.159.221.106.48837: Flags [.], seq 771601:773061, ack 154, win 127, length 1460
12:41:14.308227 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [.], ack 746781, win 1905, length 0
12:41:14.308387 IP 54.231.132.98.80 > 195.159.221.106.48837: Flags [.], seq 773061:774521, ack 154, win 127, length 1460
12:41:14.308397 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [.], ack 746781, win 1911, length 0

-> Here receiver sends a FIN, because application closed the socket (or died)
12:41:23.237156 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [F.], seq 154, ack 746781, win 1911, length 0
12:41:23.289805 IP 54.231.132.98.80 > 195.159.221.106.48837: Flags [.], seq 746781:748241, ack 155, win 127, length 1460
12:41:23.289882 IP 195.159.221.106.48837 > 54.231.132.98.80: Flags [R], seq 505782802, win 0, length 0

Anyway, getting decent speed without SACK is going to be hard.



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