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DTMF Method
After the VoIP call is connected, when you dial a digit, this digit is sent to the other side by DTMF tone.
There are two methods of sending the DTMF tone, In-band and Out-band. Choose "In-band" will send
the DTMF tone in voice packet. Choose "Out-band" will send the DTMF tone as a RTP payload signal.
Sending DTMF tone as a signal could tolerate more packet loss caused by the network. If this selection
is enabled, the DTMF tone will be sent as a signal.
Select the DTMF relay method, default setting is In-band pass through mode.
In-band
Out-band
Note
Out-of-band signaling results in a lowered high-frequency
cutoff of the effective available bandwidth.
RTP (Real-time Transport Protocol)
RTP provides end-to-end network transport functions suitable for applications transmitting real-time
data, such as audio, video or simulation data, over multicast or unicast network services. RTP does not
address resource reservation and does not guarantee quality-of-service for real-time services. The data
transport is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner
scalable to large multicast networks, and to provide minimal control and identification functionality. RTP
and RTCP are designed to be independent of the underlying transport and network layers. The protocol
supports the use of RTP-level translators and mixers.
For voice data. The In-band signaling is the sending of metadata and
control information in the same channel used for data. There are three type
of mode can be selected: In-band pass through mode, In-band PCMU
mode, and In-band PCMA mode
For RFC-2833, that is, sending the DTMF tone as a RTP payload signal.
The Out-of-band signaling has the following meanings:
1.
Signaling that uses a portion of the channel bandwidth provided by
the transmission medium, e.g., the carrier channel, which portion
is above the highest frequency used by, and is denied to, the
speech or intelligence path by filters
2.
Signaling via a different channel (either FDM or TDM) from that
used for the primary information transfer
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