AAA --Authentication, Authorization, and Accounting. AAA is a suite of network security services that provides the primary framework through which you can set up access control on your Cisco router or gateway.
ANI --Automatic number identification. Same as calling party.
DNIS --Dialed number identification service. Same as the called number.
gatekeeper --A gatekeeper maintains a registry of devices in the multimedia network. The devices register with the gatekeeper at startup and request admission to a call from the gatekeeper. An H.323 gateway is an endpoint on the LAN that provides real-time, two-way communications between H.323 terminals on the LAN and other ITU-T terminals in the WAN or to another H.323 gateway.
gateway --A gateway allows H.323 terminals to communicate with non-H.323 terminals by converting protocols. A gateway is the point where a circuit-switched call is encoded and repackaged into IP packets.
IFS --Cisco IOS file system.
IVR --Interactive voice response. When someone dials in, IVR responds with a prompt to get a personal identification number (PIN), and so on.
POTS --Plain old telephone service. Basic telephone service supplying standard single line telephones, telephone lines, and access to the PSTN.
PSTN --Public Switched Telephone Network. PSTN refers to the local telephone company.
VoIP --Voice over IP. The ability to carry normal telephone-style voice signals over an IP-based network with POTS-like functionality, reliability, and voice quality. VoIP is a blanket term that generally refers to the Cisco open standards-based (for example, H.323) approach to IP voice traffic.