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From: Patrick McHardy <kaber@trash.net>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] imprecision in bandwidth measurement
Date: Fri, 05 Dec 2003 19:44:12 +0000	[thread overview]
Message-ID: <marc-lartc-107065496214687@msgid-missing> (raw)
In-Reply-To: <marc-lartc-107064353600414@msgid-missing>

Tilman Giese (Global View) wrote:
> Hi,
> 
> I am experiencing a curious phenomenon. I limited the bandwidth for a 
> specific client to 750KBit. It works well despite of the fact that the 
> client always gets a little bit more bandwidth (around 770KBit to 
> 780KBit). I used different bandwidth and traffic measurement tools like 
> ntop, nettimer or ipac. All show the same, a little bit more bandwidth 
> than allowed. The factor by which the specified bandwidth is increased 
> seems to be proportional to the specified bandwidth. But where is the 
> problem. Is it only a different way of traffic measurement or is this a 
> bug? Maybe, does it depend on some command arguments to create the classes?


tc uses 1024 instead of 1000 as factor for kbit (1024^2 for mbit). 
Usually when talking about network equipment kbit means 1000bit/s
and mbit means 1000000bit/s. In your case, 750*24bit/s = 18000bit/s off.
The iproute-rates patch at trash.net/~kaber/hfsc is meant to fix this.

Best regards,
Patrick

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      parent reply	other threads:[~2003-12-05 19:44 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-12-05 16:51 [LARTC] imprecision in bandwidth measurement Tilman Giese (Global View)
2003-12-05 17:10 ` Stef Coene
2003-12-05 17:23 ` Tilman Giese (Global View)
2003-12-05 18:17 ` Stef Coene
2003-12-05 19:44 ` Patrick McHardy [this message]

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