[smokeping-users] The Smoke

[Tobias Oetiker]

Hi Thomas,

Today Thomas Klein wrote:

> Hello,
>
> is there a more detailed explanation available how SmokePing does draw the
> smoke into the graphs?
> I have looked into "Reading the Graphs" from the documentation, but miss some
> details:
>
> For every round of measurement smokeping sends several packets. It then sorts
> the different round trip times and selects the median, (ie. the middle one).
> This means when there are 10 time values, value number 5 is selected and
> drawn. The other values are drawn as successively lighter shades of gray in
> the background (smoke).
>
> How can i find out what the smoke will look for such example values where the
> median will be always 5?

the median is NOT always 5 ... the values get sorted and then the
middle one is picked ... the medians would look like this:

>
> Nr. 	Val1 	Val2 	Val3 	Val4 	Val5    median
> 1 	1 	1 	5 	4 	1       1
> 2 	2 	2 	5 	5 	1       2
> 3 	3 	5 	5 	5 	1       5
> 4 	4 	5 	5 	5 	1       5
> 5 	5 	5 	5 	5 	5       5
> 6 	6 	5 	5 	5 	5       5
> 7 	7 	5 	5 	9 	5       5
> 8 	8 	5 	5 	9 	5       5
> 9 	9 	5 	9 	9 	5       9
> 10 	10 	5 	10 	9 	5       9


>
> I have noted that my latency measurements tend to have more smoke above the
> median measurement than below and wonder what this does mean and how to
> interprete the graphs.

if more smoke is above than below (which is normally the case for
ping latencies) that means that every now an then a packet is
takes longer than most of the others ... but no packet is faster
than any of the others.

cheers
tobi

>
> Greetings,
> Thomas
>

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch tobi at oetiker.ch ++41 62 775 9902 / sb: -9900