From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next] tcp: ecn: dont delay ACKS after CE Date: Mon, 06 Aug 2012 14:14:51 -0700 (PDT) Message-ID: <20120806.141451.191138983583413911.davem@davemloft.net> References: <1344287083.26674.83.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org To: ncardwell@google.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:39525 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751907Ab2HFVOz (ORCPT ); Mon, 6 Aug 2012 17:14:55 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: From: Neal Cardwell Date: Mon, 6 Aug 2012 17:07:08 -0400 > On Mon, Aug 6, 2012 at 5:04 PM, Eric Dumazet wrote: >> From: Eric Dumazet >> >> While playing with CoDel and ECN marking, I discovered a >> non optimal behavior of receiver of CE (Congestion Encountered) >> segments. >> >> In pathological cases, sender has reduced its cwnd to low values, >> and receiver delays its ACK (by 40 ms). >> >> While RFC 3168 6.1.3 (The TCP Receiver) doesn't explicitly recommend >> to send immediate ACKS, we believe its better to not delay ACKS, because >> a CE segment should give same signal than a dropped segment, and its >> quite important to reduce RTT to give ECE/CWR signals as fast as >> possible. >> >> Note we already call tcp_enter_quickack_mode() from TCP_ECN_check_ce() >> if we receive a retransmit, for the same reason. >> >> Signed-off-by: Eric Dumazet >> Cc: Neal Cardwell > > Acked-by: Neal Cardwell Applied, thanks.