netdev - Re: TCP not triggering a fast retransmit?

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Date:	Wed, 30 Jun 2010 13:43:41 -0700
From:	Mitchell Erblich <erblichs@...thlink.net>
To:	Ivan Novick <novickivan@...il.com>
Cc:	netdev@...r.kernel.org, jmatthews@...enplum.com,
	Tim Heath <theath@...enplum.com>
Subject: Re: TCP not triggering a fast retransmit?


On Jun 30, 2010, at 1:14 PM, Ivan Novick wrote:

> On Wed, Jun 30, 2010 at 1:06 PM, Mitchell Erblich
> <erblichs@...thlink.net> wrote:
>> On Jun 30, 2010, at 11:04 AM, Ivan Novick wrote:
> ... snip ...
>> Sometimes, adding tracing within the tcps, can identify if.
>> the tcp flow has periods of idleness,
>> the tcp flow is/has been application limited versus network limited,
>> whether the flow is in SS or CA?
>> CA normally has DELayed ACks, which reduces the number
>>    of ACKs to 1/2 or more,
>> Whether Fast re-xmit is triggered by 2 or 3 DupAcks.
>> whether any burst avoidance has occured,
>> etc,
> 
> Hi Mitchell,
> 
> When you say adding tracing within the tcps... what method are you
> referring to, to add this tracing?  Is it some tool or setting or are
> you talking about adding custom debugging output to the kernel?
> 
> Cheers,
> Ivan

Ivan,

Custom debug code that was added into the fast-path
   when extensive tcp flow analysis is desired.
Uses a runtime /proc var to not effect the fast-path
   that by default is dis-abled.

Mitchell Erblich


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