Network Router User Manual

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Cisco IOS XE Integrated Session Border Controller Configuration Guide for the Cisco ASR 1000 Series Aggregation Services Routers
OL-15421-01
Chapter 3 DTMF Interworking
RTP to SIP Interworking
• RTP DTMF insertion—The RTP packets contain information in their headers indicating that a
DTMF is being generated. The endpoints interpret these messages and play the DTMF locally.
• In-band waveform—The DTMF is sent as part of the voice waveform.
RTP to SIP Interworking
In the case where the RTP stream is carrying the DTMF stream, the RTP packet is removed from the
stream and the DBE sends an H.248 message to the SBE indicating that a DTMF event has occurred and
that this should be converted into a SIP DTMF event.
SIP to RTP Interworking
In the case of an endpoint generating a SIP signal, the SIP DTMF signals arrive completely out of band.
An endpoint that supports SIP DTMF generates the signals to the SBE. The SBE recognizes that this is
a DTMF message and sends an H.248 message to the DBE that a DTMF tone is required to be inserted
into the RTP stream. The DBE then inserts the RTP DTMF packets into the audio stream.
Configuring Default Duration of a DTMF Event
For a complete description of commands used in this chapter, see the Cisco IOS Integrated Session
Border Controller Command Reference.
Use the dtmf-duration command in VDBE configuration mode to configure a default duration of a
DTMF event. If there is no DTMF duration configured, the system default is 200 milliseconds.
Prerequisites
Before implementing interworking DTMF, the DBE must already be created.
SUMMARY STEPS
1. enable
2. configure terminal
3. sbc {sbc-name} dbe
4. vdbe [global]
5. dtmf-duration {duration}
6. exit
7. end