1. Internet-telephony is a technology, that allows using any packet switching network based on the IP as a means of international, trunk and local calls organisation and maintanance as well as the fax transmission in real time mode.
2. H.323/RAS H.323 allows dissimilar communication devices to communicate with each other by using a standardized communication protocol. H.323 defines a common set of CODECs, call setup and negotiating procedures, and basic data transport methods. H.323RAS is registration, admission, and status. The RAS signaling protocol performs registration, admissions, bandwidth changes, and status and disengage procedures between the VoIP gateway and the gatekeeper. H.450 2/3 is the call transfer supplementary service for H.323.
3. SIP (Session Initiation Protocol) is a signaling protocol which uses text based messages and supports multimedia communications like user location, capability, availability, call setup/handling.
4. TCP/IP (Transmission Control Protocol/Internet Protocol) - is the general name for the Internet protocols stack. TCP and IP - are the most popular among them.. TCP guaranties, that every byte will be delivered to the recipient without loss. IP appoints local IP addresses to physical network addresses providing in this way address space, with which routers work
5. Codecs used in IP-telephony devices
G.711 describes the 64-kbps PCM voice coding technique. In G.711, encoded voice is already in the correct format for digital voice delivery in the PSTN or through PBXs. Described in the ITU-T standard in its G-series recommendations.
G.723.1 describes a compression technique that can be used for compressing speech or audio signal components at a very low bit rate as part of the H.324 family of standards. This CODEC has two bit rates associated with it: 5.3 and 6.3 kbps. The higher bit rate is based on ML-MLQ technology and provides a somewhat higher quality of sound. The lower bit rate is based on CELP and provides system designers with additional flexibility. Described in the ITU-T standard in its G-series recommendations.
G.729 Describes CELP compression where voice is coded into 8-kbps streams. There are two variations of this standard (G.729 and G.729 Annex A) that differ mainly in computational complexity; both provide speech quality similar to 32-kbps ADPCM. Described in the ITU-T standard in its G-series recommendations.
6. FXO Foreign Exchange Office. An FXO interface connects to the Public Switched Telephone Network (PSTN) central office and is the interface offered on a standard telephone. Cisco's FXO interface is an RJ-11 connector that allows an analog connection at the PSTN's central office or to a station interface on a PBX.
7. FXS Foreign Exchange Station. An FXS interface connects directly to a standard telephone and supplies ring, voltage, and dial tone. Cisco's FXS interface is an RJ-11 connector that allows connections to keysets, and PBX
8. PBX private branch exchange. Digital or analog telephone switchboard located on the subscriber premises and used to connect private and public telephone networks.
9. PSTN Public Switched Telephone Network. General term referring to the variety of telephone networks and services in place worldwide.
