ZyXEL Communications ZyWall USG20-VPN User Manual page 273

Chapter 14 ALG
H.323
H.323 is a standard teleconferencing protocol suite that provides audio, data and video
conferencing. It allows for real-time point-to-point and multipoint communication between client
computers over a packet-based network that does not provide a guaranteed quality of service.
NetMeeting uses H.323.
SIP
The Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol that handles
the setting up, altering and tearing down of voice and multimedia sessions over the Internet. SIP is
used in VoIP (Voice over IP), the sending of voice signals over the Internet Protocol.
SIP signaling is separate from the media for which it handles sessions. The media that is exchanged
during the session can use a different path from that of the signaling. SIP handles telephone calls
and can interface with traditional circuit-switched telephone networks.
RTP
When you make a VoIP call using H.323 or SIP, the RTP (Real time Transport Protocol) is used to
handle voice data transfer. See RFC 1889 for details on RTP.
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