9.1 General

23.1533GPPOut of band transcoder controlRelease 17Stage 2TS

Codec negotiation procedures for SIP-I are described in the following clauses, where additions or exclusions to the general procedures and principles described in the previous clauses for BICC are required; otherwise it shall be assumed that the others clauses in this specification shall apply to SIP-I on Nc. Normal call handling procedures for SIP-I on Nc are described in 3GPP TS 23.231 [20].

SIP-I codec negotiation procedures defined in the present specification extend the normal Offer/Answer rules defined by IETF RFC 3264 [24]. In order to identify the compliance to these enhancements, the 3GPP OoBTC Indicator is defined, see 3GPP TS 29.231 [21].

NOTE: Non-speech RTP payload types may also need to be negotiated within the offer/answer procedures , e.g. the Telephony Event RTP payload type or the ClearMode codec. This is further described in specific clauses in other specifications such as 3GPP TS 23.231 [20] and 3GPP TS 29.007 [19].