Patton electronic SmartNode 4110 Series manual Configuring Dtmf relay, Configuring RTP payload types

SmartWare Software Configuration Guide 47 • 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 figure 2. 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).

	Signalling of dtmf tones
encoder	payload
	decoder
Detects dtmf tones	Generates dtmf tones

Figure 2. DTMF Relay

This procedure describes how to configure DTMF relay

Mode: Profile VoIP

Step	Command	Purpose
1	node(pf-voip)[pf-name]#dtmf-relay	Define how DTMF digits shall be transmitted.
	{defaultrtpsignaling}	You can configure the SIP gateway to send
		DTMF digits either by using the SIP INFO
		method or in the RTP stream (RFC 2833). The
		gateway will always receive both types of
		DTMF digits. The command has currently no
		effect for H.323 calls.

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 Command Purpose

1node(pf-voip)[name]#rtp payload- Specifies the RTP payload-type for named tone

type nte payload-type events NTE (RFC2833). Default: 101.

VoIP profile configuration task list 579