[smokeping-users] Satellite link - Packet Loss error

[Chris Wilson]

Hi Scott,

(you might want to put your name into your mail client, to set the From 
header).

On Wed, 10 Oct 2007, mlists at pinesalad.net wrote:

> Ok.. I think I'm seeing some of the issues being discussed
> or have a couple to add.
> 
> With timeout being set to 2.5 in the config I can see
> latency being graphed as high as 16 seconds and still have
> a green 0/0 packet loss.
> 
> I was expecting fping to time out at 2.5 and this be considered a
> loss but that theory doesn't seem to be holding. Seems to be
> opposite of what Chris and Adrian were indicating when timeout is
> not used as well.

I don't think it's the opposite. If this timeout option passes "-t" to 
fping as you say, then it sets the length of time that fping will wait for 
any remaining dups/echoes/etc. after it sends the _LAST_ ping. Any
long-delayed responses to earlier pings will still be accepted before that 
timeout; so if you set the timeout to 5 seconds and send 20 pings, the 
longest delay you could ever see is 25 seconds for the first ping, 24 for 
the second, etc. At least that's my understanding of how fping works.

> With a 19/20 packet loss, I see multiple shades of gray for latency 
> plots and the red median bar not plotted in the middle of them.
> 
> Had thought there wouldn't have been any shading (i.e. smoke) with
> a 19/20 loss plot as there was only 1 packet received and where the
> red bar went would have been the result and not an average? 

Remember that 19/20 on the smokeping graph means "up to 19/20", i.e. more
than whatever the previous level is (10/20) and less than or equal to 
19/20. In other words, between 10 and 19 pings lost, or 1-10 responses. So 
there can be smoke (but not always).

Cheers, Chris.
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