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 Real-Time Control Protocol (RTCP) traffic over UDP.