Alcatel 060170-10, User Manual, Page: 31 / 430

VoIP Standards for Development
Page 1-17
VoIP Standards for Development
Alcatel’s H.323 VoIP gateway is designed to function in accordance with the following IP
Telephony and Internetworking standards currently available as briefly summarized below.
International Telecommunication Union (ITU) Standards
ITU-T technical, operational, and tariff recommendations are used for standardizing telecom-
munications on a worldwide basis. ITU H.323 IP network call control standards apply to
VoIP. These standards define the major components, namely, Telephone Terminal Equip-
ment, Gateways, Gatekeepers and Multipoint Control Units (MCUs) for H.323–based commu-
nications systems:
Series H.323 — Series H: Audiovisual and Multimedia Systems (Infrastructure of audiovisual
services — systems and terminal equipment for audiovisual services). H.323: this standard is
specifically concerned with recommendations for real time audio, video and/or data and
facsimile transmissions over H.323, Packet–based Multimedia Communications Systems. In
reference to Alcatel’s enterprise VoIP, the series as a whole relates to gateway devices used in
VoIP to handle audio, video, data and facsimile transmission over IP or packet networks. The
standard specifically includes the newer ITU recommendations for the Internet facsimile
protocol (T.38) that is used to 1) exchange messages and data between facsimile gateways
connected via an IP network, and 2) message transport (depending upon bandwidth availabil-
ity) using either TCP/IP or UDP/IP network protocols. (T.38 is incorporated into the first
release of Alcatel’s enterprise VoIP).
Series H.225 — Series H: Transmission of Non–Telephone Signals (Infrastructure of audiovi-
sual services — Transmission multiplexing and synchronization. H.225: this standard is specif-
ically concerned with recommendations for narrowband visual telephone services defined in
H.200/AV.120-Series transmission paths for local area networks (LANs) providing non-guaran-
teed quality of service (QoS) which is less than that of ISDN PRI protection and recovery
mechanisms. This recommendation describes how non-guaranteed QoS LANs provide conver-
sational services for audio, video, data and control information in H.323 equipment. The
series relates to gatekeeper devices used in VoIP to provide services across LANs. Gatekeep-
ers are centralized network devices performing IP address translations and bandwidth
management. Alcatel’s H.323 VoIP gateway uses AVNDS to work with, and in lieu of, gate-
keepers. (Note: Standard includes codec support for call synchronization.)
Series H.245 — Series H: Audiovisual and Multimedia Systems (Infrastructure of audiovisual
services — Communications procedures), Control protocol from multimedia communication.
H.245: this standard specifies syntax and semantics of terminal information messages, particu-
larly receiving and transmitting capabilities, mode preferences from the receiver, including
logical channel signaling, Control and Indication messages. Signaling acknowledgements are
specified to ensure reliable audiovisual and data communications. The series relates to Multi-
point Control Units used in VoIP to provide signaling and coding for call synchronization.
Codec Support (G.711, G.723.1, G.729a)
G.711 (PCM Encoding)
This is the ITU recommendation for an algorithm designed to transmit and receive A-Law and
Mu-Law PCM voice at digital bit rates of 48, 56, and 64 Kbps. It applies to digital telephone
sets on digital PBS (cellular) and ISDN channels. Support for this algorithm is required for
ITU-T compliant videoconferencing (the H.320/H.323 standard).