This Recommendation provides a simple yet flexible protocol for simplex, low delay applications such as far end camera control and text conversation using the LSD, HSD, and MLP channels defined in ITU-T Recs H.221 and H.243. This 2004 revised version adds a Generic Capability Object Identifier in clause 11, which enables the use of the H.224 protocol with systems according to ITU-T Rec. H.245.