2.1 Transport
The RTP/RTCP: DTMF Digits, Telephony Tones and Telephony Signals Data Extensions protocol MUST be sent using RTP as specified in [MS-RTPME] as its transport. This protocol assumes that a successful RTP session has been established with valid payload information.
The Session Description Protocol (SDP) [MS-SDP] MUST be used to negotiate the payload type information.