The present document introduces the required protocols for packet switched conversational multimedia applications within 3GPP IP Multimedia Subsystem. Visual and sound communications are specifically addressed. The intended applications are assumed to require low-delay@ real-time functionality. The present document describes the required protocol related elements for 3G PS multimedia terminal: ? required SDP signalling regarding the media type bit rate@ packet size@ packet transport frequency; ? usage of RTP payload for media types; ? bandwidth adaptation; ? QoS negotiation. The present document is applicable@ but not limited@ to packet switched video telephony. All media handling@ including codecs@ for Multimedia Telephony Service for IMS (MTSI) service is defined in [35]. This specification does not apply to MTSI. The applicability of the present document to GERAN is FFS.