The Control & Communications Standards

H.221: defines the transmission frame structure for audio visual tele services in channels of 64 to 1920 Kbps; used in H.320.

H.223: specifies a packet orientated multiplexing protocol for low bit rate multimedia communications; Annex A & B handles light and medium error prone channels of the mobile extension as used in 3G324M.

H.225: defines the multiplexing transmission formats for media stream packetisation & synchronisation on a non-guaranteed QoS LAN.
RAS (UDP): Registration, Admission, Status
H.225 - Q.931 (TCP): Call Signaling (Setup & Termination)

H.230: defines frame synchronous control and indication signals for audio visual systems.

H.242: defines the control procedures and protocol for establishing communications between audiovisual terminals on digital channels up to 2 Mbps; used by H.320.

H.243: defines the control procedures and protocol for establishing communications between three or more audiovisual terminals H.320 multipoint conferences.

H.245: defines the control procedures and protocol for H.323 & H.324 multimedia communications.
(TCP): Call Control (Capabilities, Preferences, Channel Opening and Flow Control)

RTP (UDP):media streams

H.350: LDAP authentication; LDAP endpoint setup

H.235: wider support in products; certificate support; media stream encryption