From owner-freebsd-net@FreeBSD.ORG Sat Nov 29 15:59:55 2008 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 22A0A1065675 for ; Sat, 29 Nov 2008 15:59:55 +0000 (UTC) (envelope-from venkatvenkatsubra@yahoo.com) Received: from web58307.mail.re3.yahoo.com (web58307.mail.re3.yahoo.com [68.142.236.160]) by mx1.freebsd.org (Postfix) with SMTP id C92038FC3C for ; Sat, 29 Nov 2008 15:59:54 +0000 (UTC) (envelope-from venkatvenkatsubra@yahoo.com) Received: (qmail 13927 invoked by uid 60001); 29 Nov 2008 15:59:54 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:Cc:MIME-Version:Content-Type:Message-ID; b=NLcgzuN7/eS1hA3OBvWBG5nRY5LFL4iy7GoVKG6hxJVogDcyRHynvMPSqaJOY8gY4ZjMt7/z6Y903NAkjM7RclGQGW4wW6LwJ0BVdj00F74NjhzwTESHORr8lYlFjRASowIjzLobQfPhpwWGGCeyQUjl3nC2u1TUBUNb8sexOr4=; X-YMail-OSG: F.ax8ZIVM1kTlURDH1lk8Jl620Kg4kMVIdHIcq9FvcW0rR.wbQLtxxPhNg_bP_4jf0iMo._mSHgVsrijWCzYTf_KE0kRKGsYmkFarysSbM_CcGX7k.D6RLXzx1Qi7r0KaqsWx5KO6O.nUb2ge9X3oeCiwQd42kHfcKI4jAnTOVQbbV7Rj4ttvdLr88wN Received: from [70.112.131.248] by web58307.mail.re3.yahoo.com via HTTP; Sat, 29 Nov 2008 07:59:54 PST X-Mailer: YahooMailRC/1155.32 YahooMailWebService/0.7.260.1 References: <200811281936.aa78374@walton.maths.tcd.ie> Date: Sat, 29 Nov 2008 07:59:54 -0800 (PST) From: Venkat Venkatsubra To: David Malone , Rui Paulo MIME-Version: 1.0 Message-ID: <88524.13498.qm@web58307.mail.re3.yahoo.com> Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-net@freebsd.org, Kevin Oberman Subject: Re: FreeBSD Window updates 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: Sat, 29 Nov 2008 15:59:55 -0000 Looking at some very old versions (4.3 BSD Reno for instance),=0Athe regula= r acks used to be=A0sent only through these=A0window updates.=0Ai.e. acks w= ere sent only when the apps read the data. Acks are piggybacked=0Awith wind= ow updates. Or, delayed till the delayed ack timer expires if the apps=0Ais= not reading. This would have had other issues with congestion control due = to generating=0Atoo few acks. When this was changed to send acks independen= t of apps reading the data,=0Awe=A0now have lot more acks due to these wind= ow updates in addition to the regular acks.=0A=0AVenkat=0A=0A=0A___________= _____________________=0AFrom: David Malone =0ATo: Ru= i Paulo =0ACc: freebsd-net@freebsd.org; Kevin Oberman =0ASent: Friday, November 28, 2008 1:36:04 PM=0ASubject: Re: Fr= eeBSD Window updates=0A=0A> Yes, this makes sense. Probably this is a bug s= ince 4.4BSD-Lite.=0A=0AI had a look to see what Linux does - it only genera= tes pure window=0Aupdates in the case that the advertised window would chan= ge by a=0Afactor of two. I guess this practically eliminates these updates.= =0A=0AI would guess that changing the code to update on a change of a=0Apow= er of two would be OK. Another option would be to change the=0Acurrent limi= t of two MSSes to three, because this would eliminate=0Awindow updates betw= een regular delayed ACKs.=0A=0A> So, from what I understand, we do back off= and that implies we are=A0 =0A> losing performance in the FreeBSD to FreeB= SD case, right?=0A=0AWe do the right thing and ignore these pure window upd= ates. I've=0Achecked, and Linux also ignores ACKs that just seem to update = the=0Awindow.=0A=0A=A0=A0=A0 David.=0A_____________________________________= __________=0Afreebsd-net@freebsd.org mailing list=0Ahttp://lists.freebsd.or= g/mailman/listinfo/freebsd-net=0ATo unsubscribe, send any mail to "freebsd-= net-unsubscribe@freebsd.org"=0A=0A=0A=0A