The H.323 specification describes terminals and other entities that provide multimedia communication services over packet based networks which may not provide a guaranteed QoS. H.323 entities may provide real-time audio, video and/or data communications. Support for audio is mandatory, while data and video are optional. The packet based network over which H.323 entities communicate may be a point-to-point connection, a single network segment, or an internetwork having multiple segments with complex topologies. H.323 entities may be used in point-to-point, multi-point or broadcast (as described in ITU-T H.332) configurations.