Change in osmo-gsm-manuals[master]: mncc: add note about DTMF considerations

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Harald Welte gerrit-no-reply at lists.osmocom.org
Wed Oct 3 08:30:22 UTC 2018


Harald Welte has submitted this change and it was merged. ( https://gerrit.osmocom.org/11171 )

Change subject: mncc: add note about DTMF considerations
......................................................................

mncc: add note about DTMF considerations

Add an informative note on how DTMF signalling is done in mobile
networks and mention the limitations regarding DTMF, when internal MNCC
is used.

Change-Id: Iedcf4ad5e0e4697c6a05ebdd4f43173c14c7c448
Related: OS#2777
---
M common/chapters/mncc.adoc
1 file changed, 26 insertions(+), 0 deletions(-)

Approvals:
  Jenkins Builder: Verified
  Harald Welte: Looks good to me, approved



diff --git a/common/chapters/mncc.adoc b/common/chapters/mncc.adoc
index 8825be3..3adbf7f 100644
--- a/common/chapters/mncc.adoc
+++ b/common/chapters/mncc.adoc
@@ -60,6 +60,32 @@
 Router. More widespread integration of external call routing is available via
 the OsmoSIPConnector.
 
+
+=== DTMF considerations
+
+In mobile networks, the signaling of DTMF tones is implemented differently,
+depending on the signaling direction. A mobile originated DTMF tone is
+signaled using START/STOP DTMF messages which are hauled through various
+protocols upwards into the core network.
+
+Contrary to that, a mobile terminated DTMF tone is not transfered as an out of
+band message. Instead, in-band signaling is used, which means a tone is injected
+early inside a PBX or MGW.
+
+When using {program-name} with its built in MNCC functionality a mobile
+originated DTMF message will not be translated into an in-band tone. Therefore,
+sending DTMF will not work when internal MNCC is used.
+
+For external MNCC, the network integrator must make sure that the back-end
+components are configured properly in order to handle the two different
+signaling schemes depending on the signaling direction.
+
+NOTE: osmo-sip-connector will translate MNCC DTMF signaling into sip-info
+messages. DTMF signaling in the opposite direction is not possible.
+osmo-sip-connector will reject sip-info messages that attempt to signal
+a DTMF tone.
+
+
 === MNCC protocol description
 
 The protocol follows the primitives specified in 3GPP TS 04.07 Chapter 7.1.

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Gerrit-Project: osmo-gsm-manuals
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: Iedcf4ad5e0e4697c6a05ebdd4f43173c14c7c448
Gerrit-Change-Number: 11171
Gerrit-PatchSet: 1
Gerrit-Owner: dexter <pmaier at sysmocom.de>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder (1000002)
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