[SR-Users] Request for a special parallel + serial forking scenario

[Klaus Feichtinger]

Hi,

I have a special question regarding a mixture of parallel and serial forking, operated by Kamailio-3.0.0.

First of all I will give you a short background information, what the target will be:

I have a SIP-server on place A, 3 gateways on place B and 3 gateways on place C). These gateways are registered on SIP server (A) with different Q-values (e.g. GW-B1=1.0, GW-C1=1.0, GW-B2=0.8, GW-C2=0.8, GW-B3=0.6, GW-C3=0.6). The target is, that a call for a gateway MUST be signalled on place B and C in parallel (forking) until the call is finally established over one of the two involved gateways on place B or C. When the prime gateway(s) (with the highest Q-value) fail (e.g. they do not send a provisional response within a timeout or send a negative response), the next gateway(s) should be addressed (with the next lower Q-value), a.s.o.

The configuration works well in case that both gateways on place B and C fail at the same time (BOTH do not send a response or BOTH send a negative
response or one does not send a response and the other one sends a negative response). However, in case that only ONE of the two (always in parallel) addressed gateways fails, it does not work as expected. It does nothing and/or waits for an eventually negative response or the call setup timeout.

Configuration is done as described in the README of the TM module. It is a
mixture of the main route and a failure_route in combination with the
functions t_load_contacts() and t_next_contacts().

Does anybody have an idea how this problem could be solved or any alternative solution for this special requirement of parallel signalisation in any case? 

Thanks in advance!

Regards,
Klaus

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