IMG 1010 - SIP INFO Method - Overview
Overview:
The IMG supports the SIP INFO Method. The SIP INFO Method is designed to transmit application level control information such as DTMF tones along the SIP signaling path. Transport of DTMF signaling is of great importance since there is a large existing base of DTMF applications. The transmitting of tones is accomplished during a call and is independent of the RTP or Media Stream. The mid-session signaling information is transported over the signaling path. This method allows information such as DTMF digits to be transported in a reliable way. Consider a phone banking application for example. After a user is asked by an IVR to enter an amount to be transferred the user then types the digits consecutively. If the IVR does not receive one of the DTMF digits or the digit order changes due to out-of-order delivery, the transaction may result in an unpredictable money transfer. Thus, a reliable transport channel is desired. The SIP INFO method uses the underlying SIP reliability and in-order delivery of information makes DTMF signaling resilient to unreliable packet delivery even under bursty loss.
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RFC 2976 - The SIP INFO Method
IMG 1010 - SIP INFO Method - DTMF
IMG 1010 - SIP INFO Method - SUBSCRIBE-NOTIFY