DTMF signalling does not work (with internal MNCC)
The correct transmission of DTMF tones is currently not working. I have done a series of tests, here are the results:
- unsuccessful_ms_to_ms_dtmf_tone_(NG40).pcapng: Mobile to mobile DTMF tone signalling Start and stop of the DTMF tone is acknowledged. This looks good to my perspective, probably the DTMF forwarding is not properly configured inside the NG40 tester, otherwise I would expect to see the MSC at least trying to deliver the DTMF tones to the other mobile.
- unsuccessful_ms_to_ms_dtmf_tone_with_external_mncc.pcapng: Here I can see the start command, which gets translated into a SIP message on the osmo-sip-connector. The tone also gets acknowledged and is stopped again. But again we see no response to the other MS whatsoever. This could also still be a problem with my PBX setup, since we would expect to see another SIP-Message that triggers the DTMF tone for the other MS.
- unsuccessful_ms_to_ms_dtmf_tone_with_internal_mncc.pcapng: This trace was recorded with the internal MNCC active and really looks not ok. The DTMF tone gets actively rejected.
- successful_ms_to_sip_dtmf_tone.pcapng: Here I see almost the same as in unsuccessful_ms_to_ms_dtmf_tone_with_external_mncc.pcapng, but the tone gets actually played on the other side. So I think sending DTMF tones should be fine, but receiving definetly has a problem.
- When I press buttons on the sip phone actually nothing, not even a sip-message is transmitted. That also confirms that there may be problems with the PBX.
However. I still wonder why the DTMF tones get rejected when osmo-msc is running on its internal MNCC. Something is definetly problematic there. The DTMF tone should travel back to the other end and not get rejected. I also attached the configuration files of osmo-bsc and osmo-msc. Maybe I am just lacking the right configuration options.