We do not support generating SIP INFO requests for DTMF tones.

Last year we added support for SIP KPML for OOB DTMF, which seems to be the more standard way of sending DTMF via signaling.

Standards consider INFO not appropriate for use for purposes other than for ISUP transport. Pl. see this:

http://www.jdrosen.net/papers/draft-rosenberg-sip-info-harmful-00.txt

INFO messages can be RECEIVED for DTMF but NOT TRANSMITTED for DTMF tones recevied from PSTN.

Configuration for Generation of DTMF-RELAY can be as Follows:

rtp-nte RTP Named Telephone Event RFC 2833

sip-kpml DTMF Relay via KPML over SIP SUBCRIBE/NOTIFY

sip-notify DTMF Relay via SIP NOTIFY messages

SIP INFO Method for DTMF Tone Generation

This section describes the SIP INFO Method for DTMF Tone Generation feature, which uses the SIP INFO method to generate dual-tone multifrequency (DTMF) tones on the telephony call leg. SIP methods or request message types, request a specific action be taken by another user agent or proxy server. The SIP INFO message is sent along the signaling path of the call. With the feature, upon receipt of a SIP INFO message with DTMF relay content, the gateway generates the specified DTMF tone on the telephony end of the call.

The SIP INFO Method for DTMF Tone Generation feature is always enabled, and is invoked when a SIP INFO message is received with DTMF relay content. This feature is related to the SIP NOTIFY-Basec Out-of-Band DTMF Relay Support feature, which provides the ability for an application to be notified about DTMF events using SIP NOTIFY messages. Together, the two features provide a mechanism to both send and receive DTMF digits along the signaling path.

Configuring SIP INFO Method for DTMF Tone Generation

You cannot configure, enable, or disable this feature. You can display SIP statistics, including SIP INFO method statistics, by using the show sip-ua statistics and show sip-ua status commands in privileged EXEC mode. See the following fields for SIP INFO method statistics:

•OkInfo 0/0, under SIP Response Statistics, Success, displays the number of successful responses to an INFO request.

•Info 0/0, under SIP Total Traffic Statistics, displays the number of INFO messages received and sent by the gateway.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/vvfax_c/callc_c/sip_c/sipc1_c/chapter8.htm