Configuring Dtmf Relay; Configuring Rtp Payload Types; Configuring The Dejitter Buffer (Advanced) - Patton electronics SmartNode Series Software Configuration Manual

40 • VoIP profile configuration
Configuring DTMF relay
Dual tone multi-frequency (DTMF) tones are usually transported accurately in band when using high bit-rate
voice codecs such as G.711. Low bit-rate codecs such as G.729 and G.723.1 are highly optimized for voice pat-
terns and tend to distort DTMF tones. The DTMF relay command solves the problem of DTMF distortion
by transporting DTMF tones out-of-band or separate from the encoded voice stream as shown in
H.323 signals the DTMF tones as H.245 user input indications, SIP uses a mechanism of RTP to reliably
transport tones (according to RFC2833).
This procedure describes how to configure DTMF relay
Mode: Profile VoIP
Step Command
1 node (pf-voip)[ name ]#dtmf-relay
Configuring RTP payload types
If you are using DTMF relay with SIP, the DTMF digits are transported in RTP packets with a special payload
type. The default value for this payload type can be configured in the profile VoIP.
Procedure: Configure RTP NTE payload type
Mode: Profile VoIP
Step
1 node (pf-voip)[ name ]#rtp payload-
type nte payload-type
Configuring the dejitter buffer (advanced)
Packet networks always introduce a certain amount of jitter in the arrival of voice packets. To compensate for
the fluctuating network conditions, SmartWare includes an integrated dejitter buffer in its RTP processing
engine. Typical voice sources generate voice packets at a constant rate, the matching voice decompression algo-
rithm also expects incoming voice packets to arrive at a constant rate. However, the packet-by-packet delay
inflicted by the network may be different for each packet. As shown in
packets which are sent equally spaced from the left-hand gateway arrive irregularly spaced at the right-hand
gateway,
480
Figure 80. DTMF Relay
Command
SmartWare Software Configuration Guide
Purpose
Enable DTMF relay
Purpose
Specifies the RTP payload-type for named tone
events NTE (RFC2833). Default: 101.
figure 81, the result of the delays is that
VoIP profile configuration task list
figure 80.