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Date:      Sat, 13 Nov 1999 10:04:54 +0200
From:      Barry Irwin <>
To:        Kris Kennaway <kris@hub.FreeBSD.ORG>
Cc:        ipfw@FreeBSD.ORG
Subject:   Re: TOS support for FreeBSD
Message-ID:  <>
In-Reply-To: <>; from kris@hub.FreeBSD.ORG on Fri, Nov 12, 1999 at 05:32:52PM -0800
References:  <> <>

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On Fri 1999-11-12 (17:32), Kris Kennaway wrote:
> On Fri, 12 Nov 1999, Barry Irwin wrote:
> > Hi All
> > 
> > I've been playing with some of the TOS stuff in ipchains under the 2.2.x
> > kernel series on linux, and was wondering if there was any similar
> > functionality under FreeBSD.
> > 
> > looked at the ipfw manpage on my 3.3-stable box and cant find anything
> > relevant.
> You neglected to mention what the "TOS stuff" does.
TOS is type-of-service, and is  determined by  bits 8->15 in the IP Header.
Only 4 of these bits are actually used, and stand for : miimize delay,
minimize monetary cost, maximize throughput, maximize reliability.

The net effect of setting these, is that with a TOS aware router ( such as
linux 2.2) one can use these to provide some presidence for ones IP traffic. 
The mose usefull effect I've found for this is to set minimum delay on all
my ineteractive telnet/ssh  and ftp command traffic, while assigning max
throughput to ftp-data and http traffic.  This allows me to still work with
a minimal lag to various servers I'm remotely connected to, even while my
dialup connection is runningat nearly 100% capacity, as opposed to the non
TOS  situation , of every packet takes its turn and lag becomes  terrible,
basically rendering interactive use while performing a large file download
a waste of time.

More details regarding TOS can be found in RFC 1340 (Postel) and an update
in RFC 1349 (Almquist)
Linux ipchanis allows one to modify the tos bits on a packet providing it
matches certain rules, this is the functionality I was wondering was
avaliable in FreeBSD

Hope this makes things clearer

Barry Irwin 				 	IRC:  balin@zanet (#linux)
Whois BI414		- PMPN8EZ -

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