From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matthew Pearson <matthew.pearson@infomatrix.com>
Date: Mon, 10 Apr 2006 07:52:33 +0000
Subject: Re: [LARTC] __Very__ Low Bandwidth
Message-Id: <443A0EC1.2060302@infomatrix.com>
List-Id: <lartc.vger.kernel.org>
References: <442D44FE.7070105@infomatrix.com>
In-Reply-To: <442D44FE.7070105@infomatrix.com>
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To: lartc@vger.kernel.org

Thank you Andy. I'll have another look at it and change the values to=20
get it to do what I need. Again, thank you.

Matthew Pearson

Andy Furniss wrote:
> Matthew Pearson wrote:
>> I am using the script below to simulate a very low bandwidth=20
>> connection.  I found that I could turn the bandwidth knob down to=20
>> about 4kbit, but below that I didn't get any traffic through. I've had=20
>> a look at this generally, but couldn't find an answer. It doesn't even=20
>> seem like the first reply packet gets through. I have tried it with=20
>> much bigger buffers, but this doesn't help.
>>
>> I found that if I put a web proxy on the machine that is running this,=20
>> then the minimum I can turn the bandwidth down to is 12kbit and below=20
>> that the web browser doesn't get anything back.
>>
>> Is this because the delay is so great that things are getting thrown=20
>> away by the kernel? Could I munge the packets to turn up the TTL or=20
>> something similar?
>>
>> Many thanks for some excellent tools.
>>
>> Matthew Pearson
>>
>> #!/bin/bash
>>
>> CLIENT1=192.168.1.190/32
>> CLIENT2=192.168.1.191/32
>> OPER=ADd;
>> DEV=3Deth0
>> RATE=3D3kbit
>> PEAKRATE=3D3kbit
>> BUFFER1=10kb
>> BUFFER2=10kb
>>
>> echo -e "Attach Egress policy..."
>> tc qdisc $OPER dev $DEV root handle 1:0 htb default 15
>> tc class $OPER dev $DEV parent 1:0 classid 1:1 htb rate 240kbit
>>
>> tc class $OPER dev $DEV parent 1:1 classid 1:2 htb rate 240kbit ceil=20
>> 240kbit
>> tc class $OPER dev $DEV parent 1:1 classid 1:3 htb rate 240kbit ceil=20
>> 240kbit
>> tc class $OPER dev $DEV parent 1:1 classid 1:15 htb rate 240kbit ceil=20
>> 240kbit
>>
>> tc qdisc $OPER dev $DEV parent 1:2 handle 2:0 tbf rate $RATE burst=20
>> $RATE limit $BUFFER1 peakrate $PEAKRATE mtu 1600
>=20
> I don't really get using tbf under htb - but it may be OK.
>=20
> The reason it fails <12kbit is because you use it for burst - which is a =

> buffer length so <12kbit won't pass a 1500 byte packet.
>=20
> Andy.
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