From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from shards.monkeyblade.net (unknown [IPv6:2001:4f8:3:36:211:85ff:fe63:a549]) by huchra.bufferbloat.net (Postfix) with ESMTP id A15E42005CC for ; Thu, 28 Jun 2012 22:29:35 -0700 (PDT) Received: from localhost (74-93-104-98-Washington.hfc.comcastbusiness.net [74.93.104.98]) by shards.monkeyblade.net (Postfix) with ESMTPSA id B6CC3584BD1; Thu, 28 Jun 2012 22:29:35 -0700 (PDT) Date: Thu, 28 Jun 2012 22:29:34 -0700 (PDT) Message-Id: <20120628.222934.767995619021650710.davem@davemloft.net> To: eric.dumazet@gmail.com From: David Miller In-Reply-To: <1340947448.29822.41.camel@edumazet-glaptop> References: <1340945592.29822.8.camel@edumazet-glaptop> <20120628.221252.2220466000873887315.davem@davemloft.net> <1340947448.29822.41.camel@edumazet-glaptop> X-Mailer: Mew version 6.5 on Emacs 24.0.97 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: nanditad@google.com, netdev@vger.kernel.org, codel@lists.bufferbloat.net, ycheng@google.com, ncardwell@google.com, mattmathis@google.com Subject: Re: [Codel] [PATCH net-next] fq_codel: report congestion notification at enqueue time X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 29 Jun 2012 05:29:35 -0000 From: Eric Dumazet Date: Fri, 29 Jun 2012 07:24:08 +0200 > By the way, I am not sure NET_XMIT_CN is correctly used in RED. > > Or maybe my understanding of NET_XMIT_CN is wrong. > > If a the packet is dropped in enqueue(), why use NET_XMIT_CN instead of > NET_XMIT_DROP ? > > This seems to mean : I dropped _this_ packet, but dont worry too much, I > might accept other packets, so please go on... I am pretty sure the behavior in RED is intentional. It's a soft push back on TCP. We're taking this path when we are unable to sucessfully ECN mark a packet. But our intention was to do so.