[OpenSIPS-Users] Call center issue in 3.1; call center not working after migration to 3.2

Kosmas Palios kosmas.palios at gmail.com
Tue Jul 4 10:16:14 UTC 2023

Hello community,

Our team has managed to setup a SIP Trunk to forward calls to a number of
SIP clients, in opensips 3.1.16. We are using the call center module, and
it works fine for low traffic. We would like to ask two separate but
related questions.


We are using the call center module to forward calls to 100 SIP agents, and
it works well if traffic is relatively low (about 25 incoming calls per
minute). However, when traffic is higher, i.e. up to 60 incoming calls per
minute, we see calls getting rejected because of cc_handle_call() failing
with error message:

DBG:b2b_entities:server_new: It is a retransmission, drop

ERROR:b2b_logic:b2b_process_scenario_init: failed to create new b2b server

Unfortunately, every time this happens, an agent's status gets stuck to
"incall" forever, even though no cc_calls row includes him. So that agent
is lost.

We are running in UDP mode, using 6 UDP workers. I’m attaching the
configuration file as opensips_3_1_16.cfg

I can share the whole setup if needed.


We decided to migrate to 3.2 after seeing the bugfix to b2b_clients leak.
When we got to migrating the call center, we read this blogpost:

" When comes to the modules using the b2b_logic API (providing features on
top of the B2B engine), the only affected one is the call_center module.
The change is minor – the xml file controlling the call queuing logic was
removed, as not needed any more. Otherwise, in terms of usage, it is
exactly the same."

However, when we removed the lines:


modparam("call_center", "b2b_scenario", "call center")

the call center started behaving weird: it created another invite to the
sip trunk, instead of creating the invite to the agent (the call id was
good, but the to uri was wrong). I can give detailed logs on this, but I
wouldn't want to make this email any bigger than it already is. I’m also
attaching the configuration file as opensips_3_2_13.cfg

To sum up, our questions are:

1. Any ideas on what the problem is with creating a new server instance for
high numbers of calls?

2. What's the recommended way to migrate the call center to version 3.2 ?
Can we find an example script-driven call center somewhere?

Thank you in advance for your help!

Best regards,


P.S.: about our team: we are a small team from Athens, Greece integrating
voice assistants on various platforms. Unfortunately we missed the latest
Opensips summit held last September.
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