ET> I do suspect I also have false loss in my graphs. I'm on a DSL line
ET> with multicast IPTV. The IPTV does not have any retransmitt or error
ET> correction, and I extremly rearly see any blocking in the image.
ET> Also, manual pings very rearly have any loss. But according to my 10
ET> day graphs I'm lossing 3/20.
While I suppose it's possible that smokeping is somehow not recording the
results of fping properly, I doubt highly that this is actually the case. What
does happen, I suspect, is that when it aggregates the data [as it's pruning
the RRD's from full resolution samples to the next tiers where it's grouping
more than a single sample into an "average"] it doesn't aggregate data the way
you expect.
I haven't seen a discussion about how it does this, but I'd guess that if it's
compressing ten samples into 1, for example, and one of the ten samples had 10%
loss and the others no loss, it would be better to show the loss over that
period as something like 5% or even 10%, rather than 1%. [i.e. A loss condition
is vastly more important to "see" than a no-loss condition.]
The "averaging" is probably not an average, but a "worst" case. So, if one
sample in ten had a ten percent loss, then the aggregate will show the worst
case of the aggregated samples of ten percent.
This appears to mirror what I see in my graphs. Small, irregular losses show up
more "strongly" in compressed second and third tier RRD graphs. And I think
that is how it should be.
So, if you have the occasional loss sample, as it compresses these full
resolution samples into aggregated data, you'll see more non-green
[non-zero-loss] samples than you would in the full resolution samples.
And before you complain and ask for it to be different, let me pipe in and say;
No, please don't make it different. Losses are bad, very bad. I want to have
losses emphasized, not diluted away by the other ten or twenty samples that
didn't have a loss. If your provider is losing any traffic, it's a problem and
smokeping ought to clearly call these out.
One other note on the graphs you posted. I also notice pretty strong increases
in latency during those times you don't think you're having loss. That would
correlate with what usually happens when loss actually occurs. So, I think it's
a confirmation that loss really is happening, just not in all or even most
samples.
HTH
-Greg
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