diff options
| author | Philipp Maier <pmaier@sysmocom.de> | 2018-10-01 12:56:23 +0200 |
|---|---|---|
| committer | Neels Hofmeyr <neels@hofmeyr.de> | 2018-11-27 18:34:29 +0100 |
| commit | 3130f0776a1a0082292eb2007702be7550e03525 (patch) | |
| tree | 9bbc786f7fc47cd195c00ca1f55a74c5d66d0932 | |
| parent | a001c591b36f882ae3b63020a57ce22f129cf4c0 (diff) | |
running: Add note about DTMF support
osmo-sip-connector does not yet support full DTMF support. The current
implementation only supports DTMF tones to be send from MNCC to SIP,
but not in the opposite direction.
Change-Id: I578e50b0a42d88b05cf6da80443b71494b5eb26f
Related: OS#2777
| -rw-r--r-- | doc/manuals/chapters/running.adoc | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/doc/manuals/chapters/running.adoc b/doc/manuals/chapters/running.adoc index 5e0d583..85ccddc 100644 --- a/doc/manuals/chapters/running.adoc +++ b/doc/manuals/chapters/running.adoc @@ -56,3 +56,29 @@ mncc socket-path /tmp/msc2_mncc ---- +=== DTMF signaling + +In VoIP based telephony networks DTMF (Dual-tone multi-frequency signaling) can +be signaled through multiple methods. Common methods are in-band, RFC2833 and +sip-info messages. + +Osmo-sip-connector is using sip-info messages to signal DTMF tones. When a DTMF +tone is signaled at the MNCC socket interface, osmo-sip-connector will generate +a matching sip-info message to forward the DTMF signal to the PBX. Depending on +the PBX software reconfiguring the DTMF signaling method to sip-info may be +necessary. + +While sending DTMF tones through the MNCC interface to a SIP leg, the current +implementation of osmo-sip-connector does not support sending DTMF tones in the +opposite direction. Any attempts to send DTMF tones to an MNCC leg will be +confirmed with a status 405 "Method not allowed". + +The reason for this limitation is that in mobile networks, depending on the +signaling direction, the signaling of DTMF tones is implemented differently. +A mobile originated DTMF tone is signaled through out of band messages, +which arrive at osmo-sip-connector on as MNCC DTMF START/STOP messages. Those +messages can be directly translated to sip-info messages. However, in the +other direction (mobile terminated), an in-band signaling method is used. This +means that osmo-sip-connector would have to translate an incoming DTMF sip-info +message into an audio sample that then would have to be injected into the +voice stream. Currently this scheme is not implemented in osmo-sip-connector.
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