From owner-freebsd-net@FreeBSD.ORG Wed Sep 8 18:52:32 2004 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3F3CA16A4CE for ; Wed, 8 Sep 2004 18:52:32 +0000 (GMT) Received: from mail.vicor-nb.com (bigwoop.vicor-nb.com [208.206.78.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id F082443D48 for ; Wed, 8 Sep 2004 18:52:31 +0000 (GMT) (envelope-from julian@elischer.org) Received: from elischer.org (julian.vicor-nb.com [208.206.78.97]) by mail.vicor-nb.com (Postfix) with ESMTP id F13F87A3D2 for ; Wed, 8 Sep 2004 11:52:30 -0700 (PDT) Message-ID: <413F54EE.1020700@elischer.org> Date: Wed, 08 Sep 2004 11:52:30 -0700 From: Julian Elischer User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.3.1) Gecko/20030516 X-Accept-Language: en, hu MIME-Version: 1.0 To: net@freebsd.org Content-Type: multipart/mixed; boundary="------------060900050207020902010207" Subject: [Fwd: TCP RTO] X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 08 Sep 2004 18:52:32 -0000 This is a multi-part message in MIME format. --------------060900050207020902010207 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit --------------060900050207020902010207 Content-Type: message/rfc822; name="TCP RTO" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="TCP RTO" Received: from mx2.freebsd.org (mx2.freebsd.org [216.136.204.119]) by idiom.com (8.12.11/8.12.11) with ESMTP id i88GuhuR052312 for ; Wed, 8 Sep 2004 09:56:44 -0700 (PDT) (envelope-from owner-freebsd-hackers@freebsd.org) Received: from hub.freebsd.org (hub.freebsd.org [216.136.204.18]) by mx2.freebsd.org (Postfix) with ESMTP id 0DB8556CD1 for ; Wed, 8 Sep 2004 16:56:21 +0000 (GMT) (envelope-from owner-freebsd-hackers@freebsd.org) Received: by hub.freebsd.org (Postfix) id DC3CB16A4CF; Wed, 8 Sep 2004 16:56:20 +0000 (GMT) Delivered-To: julian@freebsd.org Received: from hub.freebsd.org (localhost [127.0.0.1]) by hub.freebsd.org (Postfix) with ESMTP id C1BAF16A4D0; Wed, 8 Sep 2004 16:56:20 +0000 (GMT) Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B04C416A4CE for ; Wed, 8 Sep 2004 16:43:39 +0000 (GMT) Received: from mproxy.gmail.com (mproxy.gmail.com [216.239.56.240]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9C0BD43D45 for ; Wed, 8 Sep 2004 16:43:39 +0000 (GMT) (envelope-from shchoi@gmail.com) Received: by mproxy.gmail.com with SMTP id w67so97456cwb for ; Wed, 08 Sep 2004 09:43:36 -0700 (PDT) Received: by 10.11.119.70 with SMTP id r70mr58105cwc; Wed, 08 Sep 2004 09:43:36 -0700 (PDT) Received: by 10.11.117.28 with HTTP; Wed, 8 Sep 2004 09:43:36 -0700 (PDT) Message-ID: <34b425c504090809435a949a03@mail.gmail.com> Date: Wed, 8 Sep 2004 17:43:36 +0100 From: Soo-Hyun Choi To: freebsd-hackers@freebsd.org Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: TCP RTO X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: Soo-Hyun Choi List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: owner-freebsd-hackers@freebsd.org Errors-To: owner-freebsd-hackers@freebsd.org X-Accessio-Status: NO, score=0.00,none version=6.0 count=0 X-Accessio-Spam-Flag: NO X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on idiom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.63 X-Idiom-Reporting: If this was spam, please forward it to spambox@idiom.com Hi, I'm not sure if this list is appropriate to ask about the FreeBSD kernel source or not. If not, could somebody direct me in an appropriate list? My curiosity is if we see the tcp.cc code inside, there are two different version of srtt (smoothed rtt) and rttvar (smoothed mean deviation estimator). The one is simply 'srtt' and 'rttvar' and the other is 't_srtt' and 't_rttvar'. The unit of t_srtt is 'ticks * 8' and the unit of t_rttvar is 'ticks * 4'. These variables are used to calculate the TCP RTO. But why do they have the two different version of variables? The interesting thing is the 't_' variables are a fixed-point integer, and the original variables are just floating-point values. I assume the reason why they have is to avoid the floating-point arithmetic in the kernel. Is this really only reason for being two different version of those? Cheers, Soo-Hyun _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" --------------060900050207020902010207--