Both H.323 and SIP are multimedia conferencing protocols, which include features for voice, video, and data conferencing, for use over packet-switched networks. However, H.323 is not just an individual protocol. It is a complete implementation of a suite of protocols, which define every component of a conferencing network. The elements of H.323 include Terminals, MCUs (multipoint control units), Gateways, Gatekeepers, and other feature servers. H.323 defines a framework of how these various elements of a conferencing network function together. H.323 specifies everything including all its media codecs and how they are carried as packets in RTP or RTCP. H.323 specifies the use of Q.931 for call setup, H.225 for call signaling, and H.245 for exchanging terminal capabilities and the creation of media channels