[Asterisk-Users] Public switches (AXE10) not capable of handling sustained call setup bursts on E100P

[Scott Stingel]

Hi Knut-

This may be related to a call volume problem that I've had a lot of problems 
with in a very busy IVR environment.  I can easily duplicate this on my own 
machine by just looping one span to another. 

A colleague and I have been looking into this and believe that it may be 
related to the way the asterisk code may be handling (or not handling) under-
flow errors on the PRI frame transmitter.  Although this is ultimately 
related to load, it appears that asterisk (specifically libpri) is not 
properly handling error flags generated by the zaptel driver.  (all of this 
is theory at this point).

Mark Spencer at Digium is aware of this problem, and has said that he'll look 
at it soon.  I'm trying to develop the simplest scenario that will make this 
happen - to make it easier to debug. 

Let me know if you need my load tester script - its quite simple, but you 
would need two E1's at least to make it happen on one machine (and one or 
more E1 loopback cables)

Also suggest that you contact support at Digium directly - as this may make 
it more likely to get looked at soon.

Please let me know what kind of errors (frame retries, error 500, etc), if 
any, that you find in /var/log/asterisk/messages.

Thanks
Scott Stingel




Knut Bakke <knutbakke at yahoo.com> said:

> Hi,
> I'm running a simple test from asterisk towards a
> public telco switch (AXE10) over E100P.
> 
> Here is the test case:
> 1) 30 calls are setup simultainously, 20 sec ringing
> time. 
> 2) no calls answers (just calling a vacant public tax
> office :=)
> 3) Each channel will continue on its own with the same
> proceedure: ring for 20 sec, then hangup, ring for 20
> sec, and so on.
> 
> Of course this leads to massive signalling on the
> D-channel. 
> 
> Result:
> After one or two minutes, the number of acks from the
> public switch dropps sharply. At the end there are
> only messages in one direction (from asterisk to
> public switch), except for some RNR (Receiver Not
> Ready) message from public switch.
> 
> This leads of course to T200 timeouts, which very soon
> hits 3, and the D-channe is reset (and all calls
> terminated).
> 
> I can not see any weird behaviour from asterisk. When
> RNR is received, it stops sending setup messages to
> the far end. Which is correct.
> 
> We have managed to agree on a test session with the
> telco, but first I would like to know if anyone else
> has experienced this.
> 
> 
> Knut Bakke.
> 
> 
> 
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