[smokeping-users] How suited is Smokeping for VoIP purposes?

[Nik Mitev]

Hi Ged

On Wed, 2011-10-26 at 08:35 +0100, G.W. Haywood wrote:

> ... iptables is perhaps a
> crude tool for this sort of work and you haven't given us much else to
> go on.  Which operating systems do you use?  On what hardware are they
> running?  Apart from running Smokeping, what else are they doing?  Can
> you describe the network for us?  Is it entirely under your control?
> What continuous data throughput rate(s) can it sustain?  How many hops
> are there between endpoints?  What are the switches and routers?  Are
> they doing any kind of traffic shaping?  What are the typical round
> trip times?  Have you reduced the network to a bare minimum set of
> harware and repeated the tests?  Some time ago I had buggy hardware
> issues which limited the round trip times given by 'ping' to integer
> multiples of 4ms - have you checked that the interval timers in the
> smokeping machines are reliable?  Have you attempted to use something
> like Wireshark to monitor all the traffic on the network?  Have you
> tried inserting a router in the packet path which does nothing other
> than time the packets?  Are you running ntp on all machines involved
> so that you can make (more or less:) absolute time measurements?

The network is put together with Cisco switches and 1 or 10G links, the
average round trip times would be under 10ms and we have sufficient
bandwidth so no shaping or aggressive QoS at this point. I didn't
concentrate on the network set up and conditions because the
measurements are made from the same host to the same destination by the
same software :) The accuracy of the measurements is a separate issue as
far as it produces similar 'fuzziness' over time. The graphs can be seen
here:
http://www.mediafire.com/imgbnc.php/7a21ceb2cafbe64c4236189b62f458c007e595be963aa1a4df7a8fc0cdf55e456g.jpg
The above shows the initial result to switch1, which changed (after
adding a further probe to switch2) to a more or less flat line and then
the reproduction.

http://www.mediafire.com/imgbnc.php/4483d0cf3da608c48c2ac97ea9f703e1bf7ca3edfd0210fefbbe8434941873616g.jpg
I added a separate probe to switch1 with identical settings, but offset
by 30% so it runs shortly afterwards without overlapping. This was flat
at all times regardless of the changes in smokeping configuration.

The config files:
Probes - http://www.mediafire.com/file/4rxpbuk79dp3y9d/Probes
Targets - http://www.mediafire.com/file/w6abkbt7936kxfw/Targets


> 
> > 2. Separate scaling issue follows from FPing being limited to sending
> > pings at 1ms interval
> 
> There will always be some limit, what's the question? :)

Is there a way to avoid/circumvent the limit. In our case I will go over
the limit of 150 probes in about a year, at a guess. That is if we are
happy with basing our statistics on probes active only 10% of the time.
As a comparison, the Cisco IP SLA udp-jitter probe runs with 1000 pkts
over 20s every 60s by default - so 33% of the time.

Nik