Hi Murat, SIP INFO based DTMF is useful when state full proxy want to take some action if DTMF digits are pressed by the parties. So if the call is By pass mode (media is not passing thru server) and user press any DTMF digit, both the method (in band and TFC 2833) will be passing this information directly between UAC and UAS. Even in this case SIP INFO will still be pass thru state full proxy and hence proxy can take certain decision like forwarding, conference initiation etc.
Regards, Vishal Mathur Symantec Corporation www.symantec.com _________________________________ Office: +91-20-66067655 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Murat Artun Sent: Wednesday, June 20, 2007 2:15 PM To: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: [Sip-implementors] DTMF interoperability: In-band,RFC 2833 or SIP INFO Hello all, I want to ask about the interoperability issues for DTMF sending. There exist three ways for DTMF sending: In-band (I use this term meaning in audio as a voice data), RFC 2833 (currently 4733 obsoletes, but no change to previous procedure exists) and SIP INFO. Among these three ways, I know that only RFC 2833 is announced in the SDP of a VoIP application when it is ready to receive DTMF events as RFC 2833 packets. I have a few points to be clarified in the sense of interoperability issues: - Is it preferred that DTMF is also sent in-band and as SIP INFO when the remote VoIP application announces that it is ready to receive RFC 2833 packets? - What if the remote VoIP application does not announce that it is ready to receive RFC 2833 packets? Which method should be preferred, In-band or SIP INFO, or both for reliability purposes? - I have observed that sending DTMF as RFC 2833 packets is mostly preferred considering that sending DTMF In-band requires the remote VoIP application to perform tone detection in RTP level which requires considerable processing overhead as RFC also states. Is there a known issue about SIP INFO method for DTMF sending? Thanks in advice... -- M u r at A r t u n, MSc. Design Engineer _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
