The ITU-T Recommendation for call signaling protocols and media stream packetization for packet-based multimedia systems. See also H.320, H.323, H Series, multimedia, packet, and protocol.
An ITU standard protocol for control signaling in an H.323 audio or video environment. H.225 uses messages defined in H.245 to establish the call over the Registration, Admission and Signaling (RAS) channel. See RAS, H.245 and H.323.