netdev - Re: [PATCH] make _minimum_ TCP retransmission timeout configurable

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Message-ID: <46D5F8C0.4080801@psc.edu>
Date:	Wed, 29 Aug 2007 18:52:48 -0400
From:	John Heffner <jheffner@....edu>
To:	David Miller <davem@...emloft.net>
CC:	rick.jones2@...com, ian.mcdonald@...di.co.nz,
	netdev@...r.kernel.org
Subject: Re: [PATCH] make _minimum_ TCP retransmission timeout configurable

John Heffner wrote:
>> What exactly causes such a huge delay?  What is the TCP measured RTO
>> in these circumstances where spurious RTOs happen and a 3 second
>> minimum RTO makes things better?
> 
> I haven't done a lot of work on wireless myself, but my understanding is 
> that one of the biggest problems is the behavior link-layer 
> retransmission schemes.  They can suddenly increase the delay of packets 
> by a significant amount when you get a burst of radio interference. It's 
> hard for TCP to gracefully handle this kind of jump without some minimum 
> RTO, especially since wlan RTTs can often be quite small.

(Replying to myself) Though F-RTO does often help in this case.

   -John
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