ITU H.323 forms the foundation for audio, video, and data communications over IP-based networks. H.323 is an umbrella recommendation from the International Telecommunications Union (ITU) which defines multimedia communications over Local Area Networks (LANs) without a guaranteed Quality of Service (QoS). These networks are prevalent in today's corporate desktops and include packet-switched TCP/IP over Ethernet. H.323 suite of protocols form an important building blocks for a broad new range of collaborative, LAN-based applications for multimedia include parts of H.225.0 - RAS, Q.931, H.245 RTP/RTCP and audio/video codecs, such as the audio codecs (G.711, G.723.1, G.728, etc.) and video codecs (H.261, H.263) that compress and decompress media streams. Media streams are transported on RTP/RTCP. RTP carries the actual media and RTCP carries status and control information. The signalling is transported reliably over TCP.

This SonicWALL signature identifies legitimate H.225 UDP RAS (H.323) client to gatekeeper traffic using UDP.