From: Rick Jones <rick.jones2@hp•com>
To: netdev@vger•kernel.org
Subject: Re: TCP being hoodwinked into spurious retransmissions by lack of timestamps?
Date: Tue, 25 Mar 2014 10:39:47 -0700 [thread overview]
Message-ID: <5331BF63.6070106@hp.com> (raw)
In-Reply-To: <53151E55.9000503@hp.com>
On 03/03/2014 04:29 PM, Rick Jones wrote:
> I've been looking at some packet traces of an application looking to
> upload a Large Quantity (tm) of data to a server across the Big Bad
> Internet (tm). They've been Linux senders, and the destination while
> supporting SACK and window scaling does not support TCP timestamps. (TCP
> timestamp support was requested of the supplier of said server many many
> months ago now.)
>
> This destination system has been issuing RSTs at seemingly random points
> in the middle of a large fraction of the attempted transfers. In
> looking at the traces, they all seem to be variations on the theme of
> what is shown by:
>
> ftp://netperf.org/retrans_question/for_netdev.png
>
> which is a passing of ftp://netperf.org/retrans_question/for_netdev.pcap
> through tcptrace -nG and zoomed-in to the end. I've seen this with a
> 3.2.0 kernel as the sender, have reports of it happening with whatever
> is in Fedora Core 20, and the traces above are from a 3.11.0 kernel as
> the sender.
>
> The large quantity of (likely) unnecessary retransmissions shouldn't be
> triggering a RST by the receiver, but the failures consistently show
> that and I was wondering if the (spurious) retransmissions were perhaps
> "encouraged" (so to speak) by the lack of TCP Timestamps.
I have learned why the receiving TCP has reset the connection. It would
seem that stack has a heuristic whereby if it receives more than 255
retransmissions in a window it will abort the connection.
rick jones
prev parent reply other threads:[~2014-03-25 17:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-04 0:29 TCP being hoodwinked into spurious retransmissions by lack of timestamps? Rick Jones
2014-03-04 3:22 ` John Heffner
2014-03-04 18:50 ` Rick Jones
2014-03-04 19:14 ` John Heffner
2014-03-04 19:33 ` Rick Jones
2014-03-04 20:35 ` Neal Cardwell
2014-03-04 21:56 ` Rick Jones
2014-03-04 22:23 ` Yuchung Cheng
2014-03-04 23:14 ` Rick Jones
2014-03-21 21:53 ` Rick Jones
2014-03-25 17:39 ` Rick Jones [this message]
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