netdev - Re: [PATCH net-next] tcp: fix bogus RTT for CC when retransmissions are acked

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Date:	Sun, 12 Apr 2015 09:00:28 -0700
From:	Yuchung Cheng <ycheng@...gle.com>
To:	Neal Cardwell <ncardwell@...gle.com>
Cc:	Kenneth Klette Jonassen <kennetkl@....uio.no>,
	Netdev <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next] tcp: fix bogus RTT for CC when retransmissions
 are acked

On Sun, Apr 12, 2015 at 7:13 AM, Neal Cardwell <ncardwell@...gle.com> wrote:
> On Fri, Apr 10, 2015 at 8:17 PM, Kenneth Klette Jonassen
> <kennetkl@....uio.no> wrote:
>> Since retransmitted segments are not used for RTT estimation, previously
>> SACKed segments present in the rtx queue are used. This estimation can be
>> several times larger than the actual RTT. When a cumulative ack covers both
>> previously SACKed and retransmitted segments, CC may thus get a bogus RTT.
>>
>> Such segments previously had an RTT estimation in tcp_sacktag_one(), so it
>> seems reasonable to not reuse them in tcp_clean_rtx_queue() at all.
>>
>> Afaik, this has had no effect on SRTT/RTO because of Karn's check.
>>
>> Signed-off-by: Kenneth Klette Jonassen <kennetkl@....uio.no>
>
> Acked-by: Neal Cardwell <ncardwell@...gle.com>
> Tested-by: Neal Cardwell <ncardwell@...gle.com>
Acked-by: Yuchung Cheng <ycheng@...gle.com>
>
> neal
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