SIP User's Manual 428 Document #: LTRT-12804
Mediant 800 MSBG
8.3.4 Configuring DTMF Transport Types
You can control the way DTMF digits are transported over the IP network to the remote
endpoint, by using one of the following modes:
Using INFO message according to Nortel IETF draft: DTMF digits are carried to the
remote side in INFO messages. To enable this mode, define the following:
• RxDTMFOption = 0
• TxDTMFOption = 1
Note that in this mode, DTMF digits are erased from the audio stream
(DTMFTransportType is automatically set to 0).
Using INFO message according to Cisco’s mode: DTMF digits are carried to the
remote side in INFO messages. To enable this mode, define the following:
• RxDTMFOption = 0
• TxDTMFOption = 3
Note that in this mode, DTMF digits are erased from the audio stream
(DTMFTransportType is automatically set to 0 ).
Using NOTIFY messages according to IETF Internet-Draft draft-mahy-sipping-
signaled-digits-01: DTMF digits are carried to the remote side using NOTIFY
messages. To enable this mode, define the following:
• RxDTMFOption = 0
• TxDTMFOption = 2
Note that in this mode, DTMF digits are erased from the audio stream
(DTMFTransportType is automatically set to 0).
Using RFC 2833 relay with Payload type negotiation: DTMF digits are carried to
the remote side as part of the RTP stream in accordance with RFC 2833 standard. To
enable this mode, define the following:
• RxDTMFOption = 3
• TxDTMFOption = 4
Note that to set the RFC 2833 payload type with a different value (other than its
default), configure the RFC2833PayloadType parameter. The device negotiates the
RFC 2833 payload type using local and remote SDP and sends packets using the
payload type from the received SDP. The device expects to receive RFC 2833
packets with the same payload type as configured by the RFC2833PayloadType
parameter. If the remote side doesn’t include ‘telephony-event’ in its SDP, the device
sends DTMF digits in transparent mode (as part of the voice stream).
Sending DTMF digits (in RTP packets) as part of the audio stream (DTMF Relay
is disabled): This method is typically used with G.711 coders; with other low-bit rate
(LBR) coders, the quality of the DTMF digits is reduced. To enable this mode, define
the following:
• RxDTMFOption = 0 (i.e., disabled)
• TxDTMFOption = 0 (i.e., disabled)
• DTMFTransportType = 2 (i.e., transparent)
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