[Users] using of openser

[unplug]

Hi,
  I would like to know the typical design to use openser in order to
increase the performance.  Since openser is a proxy server and it can
be used together with another sip server to provide more function such
as asterisk.  As I have tested using sipp in a normal PC, only openser
can handle about 60 concurrent calls.  I have no idea where is the
bottleneck.  I have searched that someone will use openser with
asterisk to provide a complete (nearly) solution in voip system.  I
want to have more information about that combination, such as the
design, performance after integration, etc.  Does anyone can give me
some idea if you are using such combination?
unplug