Definition:
A voice-over—Internet protocol (VoIP) application meets the challenges of combining legacy voice networks and packet networks by allowing both voice and signaling information to be transported over the packet network. A fax-over—Internet protocol (FoIP) application enables the inter-working of standard fax machines with packet networks. It accomplishes this by extracting the fax image from an analog signal and carrying it as digital data over the packet network.

Overview:
Organizations around the world seek to reduce rising communications costs. The consolidation of separate voice, fax, and data resources offers an opportunity for significant savings. Accordingly, the challenge of integrating voice, fax, and data is becoming a rising priority for many network managers. Organizations are pursuing solutions that will enable them to take advantage of excess capacity on broadband networks for voice, fax, and data transmission, as well as utilize the Internet and company Intranets as alternatives to costlier mediums. This tutorial discusses the principles related to implementing real-time voice- and fax-over-packet networks. An overview of the embedded software architecture is presented, and a system is described for sending voice, fax image, data, and signaling information over the packet network. Benefits to designers and manufacturers of this embedded approach are lower cost of goods sold, faster time to market, and lower development costs. Customers can gain a considerable advantage in time to market in building their communication systems. This tutorial references a general class of packet networks, as the modular software objects allow networks such as asynchronous transfer mode (ATM), frame relay, and Internet/intranet (Internet protocol [IP]) to transport voice and fax. Currently, the Frame Relay Forum and the International Telecommunication Union (ITU) have defined protocols for transmission of fax over a packet network. However, the principles described are equally applicable to ATM networks.