From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net 3/3] tcp: do not delay ACK in DCTCP upon CE status change Date: Wed, 18 Jul 2018 14:44:05 -0700 Message-ID: <70a585a2-c276-73f7-591e-ae4eb883a075@gmail.com> References: <20180718205636.210731-1-ycheng@google.com> <20180718205636.210731-4-ycheng@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, edumazet@google.com, ncardwell@google.com, brakmo@fb.com, ysseung@google.com To: Yuchung Cheng , davem@davemloft.net Return-path: Received: from mail-pg1-f195.google.com ([209.85.215.195]:39673 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730331AbeGRWX4 (ORCPT ); Wed, 18 Jul 2018 18:23:56 -0400 Received: by mail-pg1-f195.google.com with SMTP id g2-v6so2587951pgs.6 for ; Wed, 18 Jul 2018 14:44:06 -0700 (PDT) In-Reply-To: <20180718205636.210731-4-ycheng@google.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 07/18/2018 01:56 PM, Yuchung Cheng wrote: > Per DCTCP RFC8257 (Section 3.2) the ACK reflecting the CE status change > has to be sent immediately so the sender can respond quickly: > > """ When receiving packets, the CE codepoint MUST be processed as follows: > > 1. If the CE codepoint is set and DCTCP.CE is false, set DCTCP.CE to > true and send an immediate ACK. > > 2. If the CE codepoint is not set and DCTCP.CE is true, set DCTCP.CE > to false and send an immediate ACK. > """ > > Previously DCTCP implementation may continue to delay the ACK. This > patch fixes that to implement the RFC by forcing an immediate ACK. Oh well, more ACK packets ;) Signed-off-by: Eric Dumazet