1.1. VoIP Overview

Voice over IP (VoIP) can be described as the ability to make telephone calls and send faxes over IP-based data networks with a suitable Quality of Service (QoS). The voice information is sent in digital form using discrete packets rather than via dedicated connections as in the circuit-switched Public Switch Telephone Network (PSTN). At the time of writing this document, there are two major international groups defining standards for VoIP:

• International Telecommunications Union (ITU) - The ITU has defined the H.323 standard, which covers VoIP.
• Internet Engineering Task Force (IETF) - The IETF has defined drafts of the following RFC (Request for Comment) documents:
  • RFC 2543, the Session Initiation Protocol (SIP)
  • RFC 27053, the Media Gateway Control Protocol (MGCP)
  • RFC 3015, Megaco Protocol Version 1.0 (Megaco)

The H.323 standard was developed in the mid 1990s and is more mature than any of the protocols mentioned above.

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