Date: Wed, 08 Sep 2004 11:52:30 -0700 From: Julian Elischer <julian@elischer.org> To: net@freebsd.org Subject: [Fwd: TCP RTO] Message-ID: <413F54EE.1020700@elischer.org>
next in thread | raw e-mail | index | archive | help
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 <julian@elischer.org>; 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 <julian@elischer.org>; 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 <freebsd-hackers@freebsd.org>;
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 <freebsd-hackers@freebsd.org>;
Wed, 8 Sep 2004 16:43:39 +0000 (GMT)
(envelope-from shchoi@gmail.com)
Received: by mproxy.gmail.com with SMTP id w67so97456cwb
for <freebsd-hackers@freebsd.org>;
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 <shchoi@gmail.com>
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 <shchoi@gmail.com>
List-Id: Technical Discussions relating to FreeBSD
<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>;
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
<mailto:freebsd-hackers-request@freebsd.org?subject=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--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?413F54EE.1020700>