Communicating via packet data networks such as IP, ATM, and Frame Relay has become a preferred strategy for both corporate and public network planners. Experts are predicting that data traffic will soon exceed telephone traffic, if it hasn't already. At the same time, more and more companies are seeing the value of transporting voice over IP networks to reduce telephone and facsimile costs and to set the stage for advanced multimedia applications. Providing high quality telephony over IP networks is one of the key steps in the convergence of voice, fax, video, and data communications services. Voice over IP has now been proven feasible; the race is on to adopt standards, design terminals and
gateways, and begin roll-out of services on a global scale.

Voice and telephone calling can be viewed as one of many applications for an IP network, with software being used to support the application and interface to the network. The emergence of VoIP is a direct result of the advances that have been made in hardware and software technologies in the early 1990s.
The software functionality required for voice-to-packet conversion in a VoIP terminal or gateway are:

• The Voice Processing module, which prepares voice samples for transmission over the packet network. This software is typically run on a DSP.
• The Call Processing (Signaling) module, which serves as a signaling gateway allowing calls to be established across the packet network. This software supports E&M (wink, delay and immediate), loop, or ground start FXS and FXO.
• The Packet Processing module, which processes voice and signaling packets, adding the appropriate transport headers prior to submitting the packets to the IP network (or other packet networks). Signaling information is converted from telephony protocols to the packet signaling protocol.
• The Network Management module, which provides management agent functionality, allowing remote fault, accounting, and configuration management to be performed from standard management systems. The Network Management
module could include ancillary services such as support for security features, access to dialing directories, and remote access support.