H.323 is a standard that specifies the components, protocols and procedures that provide multimedia communication services—real-time audio, video, and data communications—over packet networks, including Internet protocol (IP)–based networks. H.323 is part of a family of ITUT recommendations called H.32x that provides multimedia communication services over a variety of networks.
This tutorial discusses the H.323 protocol standard. H.323 is explained with an emphasis on gateways and gatekeepers, which are components of an H.323 network. The call flows between entities in an H.323 network are explained, and the interworking aspects of H.323 with H.32x family protocols are discussed.