netdev - Re: 200 millisecond timeouts in TCP

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Date:	Thu, 3 Jun 2010 17:11:07 -0700
From:	Ivan Novick <novickivan@...il.com>
To:	Hagen Paul Pfeifer <hagen@...u.net>
Cc:	netdev@...r.kernel.org
Subject: Re: 200 millisecond timeouts in TCP

On Thu, Jun 3, 2010 at 4:10 PM, Hagen Paul Pfeifer <hagen@...u.net> wrote:
> * Ivan Novick | 2010-06-03 15:37:24 [-0700]:
>
>>Using tcpdump and systemtap I am seeing that sometimes retransmission
>>of data is sent after waiting 200 milliseconds.  However sometimes
>>retransmissions happen quicker.
>
> Quicker as 200ms? Conservatively the minimum TCP RTO should be 1s (rfc2988),
> Linux differs from this default and define the minimum RTO to 200ms:
>
> #define TCP_RTO_MIN     ((unsigned)(HZ/5))
>
> Can you post the tcpdump traces where the relevant retransmission is recognizable?

resending tcpdump output as attachments.

Cheers,
Ivan Novick

Download attachment "dell1.tcpdump" of type "application/octet-stream" (6295 bytes)

Download attachment "dell2.tcpdump" of type "application/octet-stream" (8679 bytes)