From owner-freebsd-net@FreeBSD.ORG Fri Sep 28 11:47:01 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 803C61065670 for ; Fri, 28 Sep 2012 11:47:01 +0000 (UTC) (envelope-from andrey@zonov.org) Received: from mail-la0-f54.google.com (mail-la0-f54.google.com [209.85.215.54]) by mx1.freebsd.org (Postfix) with ESMTP id E84D98FC17 for ; Fri, 28 Sep 2012 11:47:00 +0000 (UTC) Received: by lage12 with SMTP id e12so1230501lag.13 for ; Fri, 28 Sep 2012 04:46:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :x-gm-message-state; bh=BX2xiBYxvhaXmLkYRD6LeVvs/jl7jWwfRjfpFle2R+Y=; b=S6l/RV1YMFj/IqAIXSFq7tF+pVFIp8H0FWv0zVM/0iwF0sU4t38gTIrliwDISD1F1t nZn/u7DwUcDnysv5Dt6AwDNCC48wXxJvFe9/7K3H5wVenKY0wek/sUbm7WObLnPS3Hkw Dh0ewE+MLEvGJkVg6eSq2w/L8xiiJCJbFWSyIzDg8oM1vQ4nCb1+VRmmHUs80casRSVf m8AWtY32RmmQBqcU6XBR6KHpK9Ty1AnkLScT+u7jL6DeL7VnfGFal5Yz0rAhpmnoLLu4 dn35ILOKqZqzF0974lu3jnoLfKPJ/TFGg/jJFv6QQXe98tkRhyh0HzxAJ5qAQN8ydvV+ t9bA== Received: by 10.152.112.37 with SMTP id in5mr5598711lab.44.1348832819011; Fri, 28 Sep 2012 04:46:59 -0700 (PDT) Received: from dhcp170-82-red.yandex.net (dhcp170-82-red.yandex.net. [95.108.170.82]) by mx.google.com with ESMTPS id d1sm2433783lbh.7.2012.09.28.04.46.57 (version=SSLv3 cipher=OTHER); Fri, 28 Sep 2012 04:46:58 -0700 (PDT) Sender: Andrey Zonov Message-ID: <50658E2E.5010602@FreeBSD.org> Date: Fri, 28 Sep 2012 15:46:54 +0400 From: Andrey Zonov User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:15.0) Gecko/20120907 Thunderbird/15.0.1 MIME-Version: 1.0 To: Andre Oppermann References: <505AC500.6060903@FreeBSD.org> <505F2C2D.5050904@FreeBSD.org> <50634F85.50901@networx.ch> In-Reply-To: <50634F85.50901@networx.ch> X-Enigmail-Version: 1.4.4 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig3043F80B35A7FB0F99E87D09" X-Gm-Message-State: ALoCoQmOaZyb1KnJ6rCLhUsA5Ai4AdmEO2+6+qZYun3C6pXR123/YpxW59u6W0X+cVXeEO84vSyR Cc: "freebsd-net@freebsd.org" , "Eggert, Lars" Subject: Re: [patch] sysctls for TCP timers X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 28 Sep 2012 11:47:01 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig3043F80B35A7FB0F99E87D09 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 9/26/12 10:55 PM, Andre Oppermann wrote: > On 23.09.2012 17:35, Andrey Zonov wrote: >> On 9/20/12 11:35 AM, Eggert, Lars wrote: >>> Hi, >>> >>> On Sep 20, 2012, at 9:25, Andrey Zonov wrote: >>>> Some of them may be read google's article about tuning TCP parameter= s >>>> [1]. I convert most of TCP timers to sysctls [2] and we are using t= his >>>> patch for few months. We tuned net.inet.tcp.rtobase and >>>> net.inet.tcp.syncache.rexmttime and it gives good results >>>> (especially in >>>> conjunction with cc_htcp(4)). >>> >>> can you share some measurements that quantify the results? >>> >> >> When we set net.inet.tcp.syncache.rexmttime=3D200 and >> net.inet.tcp.syncache.rexmtlimit=3D7 for our external web service, the= >> number of duplicated SYN was reduced in four times. >=20 > This isn't surprising. You're simply trading retransmits by the client= > with retransmits by the server. Whether this is within the overall pac= ket > conservation principle is not clear. On the timeline it may be an > advantage. >=20 This is great improvement for us. 2% of our users don't wait for 3 seconds any more. > I'm not comfortable with the rather low retransmit time you've chosen > here. Considering higher RTT's (e.g. Hawaii or JP/CN) and the bufferbl= oat > problem this may be too low. When it is to be tuned, then something in= the > range of 500-1000ms may be more realistic to avoid spurious retransmits= =2E >=20 For example Linux some time ago set RTO to 1 sec. OSX for a long time has RTO 1 sec. > When a SYN or SYN/ACK retransmit happens, the initial CWND should be > reduced > per the applicable RFC's as this indicates packet loss on the downstrea= m. >=20 --=20 Andrey Zonov --------------enig3043F80B35A7FB0F99E87D09 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.18 (Darwin) Comment: GPGTools - http://gpgtools.org iQEcBAEBAgAGBQJQZY4wAAoJEBWLemxX/CvTaIsIAIGxsw4aWCYF+1CuLXkNrIgP K5KPjeIKSo7Um+jJNUAz8hFxepbEf3Y4AFGY2Y98NQHCJKxHi+bUmNZrC3Svs6CV 1MdUEeDGjSp9k9Ef5zrZaWzKhmzQPlxZ+DtamksMOzM03OWD0cIqixP/2UNr2/C/ 9JlcEOJpER2AlRxyJ+8+6bWJH33RDBF7C4vZcCDSfxjsvBhwWOGScMhuqh69Xmef /ixU8uYRGOWZaw3T1tv6oItChBOaSjF+Wv8VBpkt82uFswccHLfRmvAor7Lu/IoZ ASg5/1l1TLAbttRw9zMiAQHWyPQtVbjI3xqwilK6QMvzTESoBtX35sO1PXe5tKo= =MT2u -----END PGP SIGNATURE----- --------------enig3043F80B35A7FB0F99E87D09--