Technology Standards for VoIP

By Kristine Hegglin
Updated: January 31, 2011

Voice over Internet Protocol (VoIP) technology standards must be flexible because VoIP equipment must interoperate with a variety of technologies and protocols. The most accepted VoIP protocol standard is H.323. H.323 is a protocol standard created for call communication and provides specific information on call signaling control, multimedia control, and bandwidth control. This standard is recommended by the ITU Telecommunication Standardization Sector (ITU-T).


H.323 standards excel in multimedia communication over Internet Protocol (IP) networks. Besides the H.323 protocol standard, VoIP equipment must be enabled to interact with other protocols, which are used to transmit voice and multimedia communications over the Internet. These protocols include Session Initiated Protocol (SIP) and Media Gateway Control Protocol (MGCP). SIP enables the creation, modification and termination of Internet telephone sessions, Internet distribution of multimedia, and internet multimedia conferences. The MGCP protocol addresses worldwide gateway control and enhances the H.323 protocol along with the SIP protocol.

Besides protocols, the manufacturers of VoIP devices must enable their products to work with telephony signaling standards. Some of these telephony signaling standards include:

  • Ethernet network interfaces
  • Foreign eXchange Subscriber interfaces/Foreign eXchange Office interfaces (FXS/FXO)
  • Integrated Services Digital Network (ISDN)
  • Primary Rate Interface (PRI)
  • ISDN Basic Rate Interface (BRI).

FXS/FXO are ports used by analog phones. PRI is an accepted standard for office-based telecommunication services. PRI is based on the T-carrier (T1) line and the E-carrier (E1) line. The T1 line is used in the United States and the E1 line is used in Europe.

VoIP technology is enabled to interface with Private Branch Exchange (PBX) systems. PBX systems are private telephone networks used within an organization. With a PBX system, outside phone lines are shared by all employees so that external phone calls may be made to Plain Old Telephone System (POTS) lines. The PBX connects the telephone lines within an organization to the Public Switched Telephone Network (PSTN). VoIP PBX, also called IP PBX, is a very popular communication solution among organizations. This VoIP solution uses IP addresses to transmit calls. Simple telephony systems only need gateways implemented to encode or decode voice signals for the PBX. Elaborate systems for large organizations will most likely need IP PBX.

As technology evolves, VoIP technology standards will too. VoIP equipment manufacturers will need to be prepared to make the necessary changes to be competitive. And, VoIP vendors will need to remain flexible in order to remain competitive in the market. What’s nice about a VoIP system is that is can be integrated with a company’s existing analog system. This compatibility makes VoIP systems even more appealing. In the future, we’ll most likely see more and more VoIP capabilities, integration, and technology compatibility.

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