This Recommendation covers the frame structure, elements of procedure and formats to support a real time control (ITU-T Rec. H.224) protocol primarily used in multipoint videoconference networks using the H.243 broadcast capability of the H.221 LSD/HSD channels or the H.221 MLP data channel. H.224 frames are encapsulated in Q.922 Unnumbered Information (UI) frames, referred to as I mode for the remainder of this Recommendation.