Open Stack

Hi,

Thanks Russel, Paul, and everyone else who helped with the Asterisk
testing on Friday.  Here's how I see the outcome:

The main problem we're trying to solve is that the audio is sometimes
choppy.

We found that moving the PBX to some specific Rackspace vms improved the
situation.  Moving to an 8g vm in the same dc did not improve the
situation; moving to a 30g vm in the same dc did improve it.

Moving to a small vm in a new dc which is lightly loaded also did
improve it.  And finally, moving to a small vm in HPCloud also improved
it.

This leads me to believe that the load on the host hardware affects this
problem, possibly due to additional latency in providing cpu time
slices.  The fact that both using a larger VM (which reserves more of
the host's resources) and a less heavily loaded data center (less
competition for host resources) improved things points in this
direction.

After this test, Paul disabled the silence suppression, and when we
moved back to our original vm, the problem did not manifest.  Combining
this result with the above suggests to me that perhaps the silence
suppression algorithm is particularly sensitive to cpu latency.

Regardless, here are some possible next steps:

* Move Asterisk to a 30g vm in Rackspace (in either our current or the
  new data center).  This appears to reserve a large enough CPU capacity
  to help with the problem, though it's possible future host load
  changes may still affect us.

* Move Asterisk to a vm in HPCloud.  This has the additional downsides
  that we can provide no IPV6 service, the Asterisk (and network)
  configuration becomes more complicated due to NAT, and HPCloud still
  occasionally terminates vms without warning.  It is also possible here
  that future host load changes may affect us (but that is more
  speculative since we haven't seen evidence of that so far).

* Disable silence suppression in the conference server.  This appears to
  have a much smaller effect on load than we anticipated (we tested with
  60 participants and did not observe a problem).  However, silence
  suppression is useful on large calls to reduce background noise from
  non-speakers.

Does anyone have any other observations or suggestions?

-Jim