C.3 Describing the RTP payload Type in SDP

29.0073GPPGeneral requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)Release 17TS

The "vnd.3gpp.clearmode" RTP payload shall be described in SDP (see IETF RFC 4566 [98]) as follows.

– The MIME type ("audio") shall be used in the SDP "m=" line as the media name

– A dynamic RTP payload type number shall be used in the SDP "m=" line.

– The meaning of the dynamic RTP payload type number shall be described by supplying "vnd.3gpp.clearmode" as MIME subtype within an SDP "rtpmap" attribute.

– If supplied, the optional parameter "ptime" shall be encoded as "ptime" SDP attribute.

– If supplied, the optional parameter "maxptime" shall be encoded as "maxptime" SDP attribute.

– If supplied, the optional parameter "network-initiated-service-change" shall be encoded within the "fmtp" SDP attribute. No values for the parameter shall be supplied.