From: Joris van Rantwijk <joris@jorisvr.nl>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: Question about LRO/GRO and TCP acknowledgements
Date: Sun, 12 Jun 2011 11:30:04 +0200 [thread overview]
Message-ID: <20110612113004.79f48f40@konijn> (raw)
In-Reply-To: <1307869632.2872.106.camel@edumazet-laptop>
On 2011-06-12, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > As far as I can see, current code will send just one ACK per
> > coalesced GRO bundle, while the sender expects one ACK per two
> > segments.
> One ACK carries an implicit ack for _all_ previous segments. If sender
> only 'counts' ACKs, it is a bit dumb...
It may be dumb, but it's what the RFCs recommend and it's what Linux
implements.
RFC 5681:
"During slow start, a TCP increments cwnd by at most SMSS bytes for
each ACK received that cumulatively acknowledges new data."
In Linux, each incoming ACK causes one call to tcp_cong_avoid(),
which causes one call to tcp_slow_start() - assuming the connection is
in slow start - which increases the congestion window by one MSS.
Am I mistaken?
Please note I'm talking about managing the congestion window.
Of course I agree that each ACK implicitly covers all previous segments
for the purpose of retransmission management. But congestion
management is a different story.
Joris.
next prev parent reply other threads:[~2011-06-12 9:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-11 19:59 Question about LRO/GRO and TCP acknowledgements Joris van Rantwijk
2011-06-12 3:43 ` Ben Hutchings
2011-06-12 7:51 ` Joris van Rantwijk
2011-06-12 9:07 ` Eric Dumazet
2011-06-12 9:30 ` Joris van Rantwijk [this message]
2011-06-12 10:48 ` Eric Dumazet
2011-06-12 11:24 ` Joris van Rantwijk
2011-06-12 12:01 ` Alexander Zimmermann
2011-06-12 14:57 ` Eric Dumazet
2011-06-12 19:37 ` Joris van Rantwijk
2011-06-14 10:53 ` Ilpo Järvinen
2011-06-14 19:37 ` Joris van Rantwijk
2011-06-13 17:55 ` Rick Jones
2011-06-13 17:34 ` Rick Jones
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