netdev - Re: [PATCH] tcp: ECN blackhole should not force quickack mode

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Message-ID: <1317025614.2557.7.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Mon, 26 Sep 2011 10:26:54 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	jhs@...atatu.com
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>, Jerry Chu <hkchu@...gle.com>,
	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
	Jim Gettys <jg@...edesktop.org>,
	Dave Taht <dave.taht@...il.com>
Subject: Re: [PATCH] tcp: ECN blackhole should not force quickack mode

Le dimanche 25 septembre 2011 à 21:13 -0400, jamal a écrit :
> On Sun, 2011-09-25 at 21:07 -0400, jamal wrote:
> 
> > In regards to the 'linux funny extension' - this was a brilliant idea
> > in my opinion back then from Alexey; lots of discussions happened but
> > I cant remember if it made it in some RFC or not (I will try to search
> > some old archives).
> 
> Wasnt hard:
> https://tools.ietf.org/id/draft-ietf-tsvwg-tcp-ecn-00.txt
> It doesnt seem to have made it to RFC and i cant remember why.
> [We dont wanna bring Sally out of retirement but we can ask KK if
> it bugs you;->]

Thanks !

This refers to additions to RFC 2481 : This was refined by RFC 3168, and
the retransmitted TCP packets requirement is part of the final RFC :

6.1.5.  Retransmitted TCP packets

   This document specifies ECN-capable TCP implementations MUST NOT set
   either ECT codepoint (ECT(0) or ECT(1)) in the IP header for
   retransmitted data packets, ...

Followed by a very long description :)

BTW, the ECN+ proposal (RFC 5562 :  Adding Explicit Congestion
Notification (ECN) Capability to TCP's SYN/ACK Packets) would allow the
client (receiving SYNACK message with ECT flags) to set the TCP_ECN_SEEN
I added in my patch, allowing even the first (retransmitted) data packet
to trigger quickack mode.

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