ZyXEL Communications ZYWALL USG 2000 Manual page 312

Chapter 18 ALG
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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ZyWALL USG 2000 User's Guide