SIP And DTMF SIP WG 48 th IETF

SIP And DTMF SIP WG 48 th IETF July 31 -August 4, 2000 Bert Culpepper, Skip Cave 48 th IETF SIP WG

DTMF Related Proposals • The SIP INFO Method – draft-ietf-sip-info-method-04. txt – Draft describes the use of the SIP INFO Method for mid-call signaling along the SIP signaling path. DTMF is one data type described. • Sample Uses of SIP INFO with Varying Reliability Needs – draft-kuthan-sip-infopayload-00. txt (expired) – Draft describes mid-session signaling and reliable in-order delivery using the SIP INFO method. Describes DTMF digit strings in INFO message bodies. Suggests MGCP/Megaco MIME content support in Gateway Controllers. 48 th IETF SIP WG 2

DTMF Transmission Techniques • Contained in Media (RTP Stream) – Doesn’t work with compressed media. – Requires “ports” in service platforms. • Special Encoding in RTP (RFC 2833) – Can be sent separate from other media (Supports 3 pcc). – Requires RFC 2833 encoder/decoder. • RFC 2833 Encoded Data Using INFO Method – Can be sent along the call signaling path (Supports 3 pcc). – Requires RFC 2833 encoder/decoder. • DTMF Using INFO Method (draft-choudhuri-sip-info-digit-00. txt) – – 48 th IETF Can be sent along the call signaling path (Supports 3 pcc). Text-based encoding of DTMF. No “out-of-order” issues. Draft goes beyond DTMF transmission by describing collection attributes to be used by a client. SIP WG 3

DTMF Transmission Techniques (cont. ) • MGCP/Megaco-Based Event Detection and Reporting Using INFO Method (draft-culpepper-sip-info-event-00. txt) – – Can be sent along the call signaling path (Supports 3 pcc). MGCP/Megaco text-based encoding of DTMF. No “out-of-order” issues. Specific to networks containing MGCP/Megaco-based Media Gateways and Media Gateway Controllers. – Goes beyond DTMF transmission by describing MGC enabled event detection and reporting at the MG. Leverages MGCP/Megaco compliant DTMF collection and reporting capabilities. 48 th IETF SIP WG 4

Preferred Support Mechanism in SIP • Recent discussions on the SIP list indicate preferred method for DTMF transmission is RFC 2833 encoded packets transported via RTP. • However, it’s still not a “closed” issue. Issues to Consider • DTMF in a packet network is application control. • Session-related Services Platforms require user interaction independent of the primary media. (When voice recognition is not employed by the service. ) • SIP is the IETF protocol currently carrying telephony signaling around a packet network (there is MGCP/Megaco at the edges). And in this role, mid-call signaling in SIP can support carrying today's PSTN enhanced services. However, other protocols exist for control and event reporting capabilities. 48 th IETF SIP WG 5