H.323 is the result of an International Telecommunications Union (ITU) specification for computers, equipment and services concerned with multimedia communications over networks that fail to offer a guaranteed quality of service. H.323 allows for the transmission of real time video, audio and data and has been specifically designed to provide the protocols that need to be observed in order to make available audio-visual communications on any packet network. In addition the H.32x series of Protocols encapsulate H.323 in order to provide services over ISDN, PSTN or SS7. H.323 provides a similar function to that of the Session Initiation Protocol when used in Voice Over Internet Protocol (V0IP), Internet telephony or IP Telephony. Early availability of H.323 provided a ready made set of standards that not only detailed the basic call model it also addressed issues relating to business communications expectations.