[mrtg] Re: Burst traffic

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Fri Dec 14 18:53:18 MET 2001

Alejandro Cabrera Obed wrote:

> I have a MRTG software monitoring a 128 Kbps (16KBps) dedicated link to my
> ISP (LMDS technology).
> Sometimes when I downloaded a program from Internet, in the graphics that
> MRTG builds, it appears some peak rates of 26 KBps ( greater than the 16
> KBps of my link capacity).

128 kbps is a logical limit, not a technical limit.  At least, that's
my guess.

> Technical support from my  ISP say that it is a "burst", but they didn't say
> what's the cause of this behavior.
> I ask you: what is the cause of a burst traffic in a link and when it occurs
> ????

The following numbers will not be accurate and so is the description.
It does however show what might happen.

Suppose you want to download something that's 32 kilobytes.  It would
normally take 2 seconds to download it at a speed of 128 kbps:
32 kilobytes is 256 kilobits, 256 is 2 times 128.

Now suppose your link can actually transfer at a higher rate than
128 kbps.  Suppose it is 256 kbps.  In stead of transfering the file
at a rate of 128 kbps it is downloaded at 256 kbps.  The next second
you don't transfer anything at all.  On average you have still reached
an *average* rate of 128 kbps (256 kbit in two seconds) however the peak
rate is higher than 128 kbps.

Apply this example at a larger time range and you may actually find
yourself in a situation where you happen to monitor this higher rate.

On average you will be limited to the 128 kbps, this however is not
necessarily your technical maximum.

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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