ing protocols and media stream packetization for packet-based multimedia communications systems. H.226 Part of the ITU-T's H.32x Recommendation, H.226 establishes channel aggregation protocols for multilink operation on circuit-switched networks. H.230 A multiplexing Recommendation that is part of the ITU-T family of video interoperability Recommendations. Formally known as "Frame- synchronous Control and Indication Signals for Audiovisual Systems," the Recommendation specifies how individual frames of audiovisual information are Glossary of Terms to be multiplexed onto a digital channel. H.231 ITU Recommendation, formally known as "Multipoint Control Unit for Audiovisual Systems Using Digital Channels up to 2 Mbps," H.231 was added to the ITU-T's H.320 family of Recommendations in March 1993. It specifies the multipoint control unit used to bridge three or more H.320-compliant codecs together in a multipoint conference. H.235 Formerly known as H.SECURE, H.235 was ratified in February 1998 to establish security and encryption protocols for H.323 and other H.245-based multimedia terminals. H.235 is not itself a method of encryption and security, but establishes a methodology for leveraging such protocol families as IPSec (that, in turn, leverages security association and key distribution protocols such as ISAKMP and Oakley). H.242 Part of the ITU-T's H.320 family of video interoperability Recommendations Formally known as the "System for Establishing Communication Between Audiovisual Terminals Using Digital Channels up to 2 Mbps," H.242 specifies the protocol for establishing an audio session and taking it down after the communication has terminated. H.243 ITU-T "System for Establishing Communication Between Three or More Audiovisual Terminals Using Digital Channels up to 2 Mbps." H.245 Part of the ITU's H.324 protocol that defines control of communications between multimedia terminals. Its formal Recommendation name is "Control protocol for multimedia communication." H.246 ITU recommendation to establish a method