ced in the early 1990s, by AT&T Solutions, you will have to purchase your the data technology was not originally designed to carry own VoFR equipment. Most of the major router ven- voice. Despite valid reservations about the reliability of dors, including 3Com Corp., Avaya Inc., Lucent Tech- voice over frames, the promise of "free voice" eventually nologies, Cisco Systems Inc., and Nortel Networks proved too alluring. Soon users were experimenting with Corp., offer routers, switches, or voice-enabled frame transporting voice over their Frame Relay devices while relay access devices (VFRADs). equipment vendors worked overtime to make the Voice switching is the technology that enables us to promise of quality VoFR a reality. dial a telephone number and reach the desired destina- As the public Internet exploded in the mid-1990s and tion. It implements the signaling required to establish, users began implementing IP-based networks, the call for maintain, and tear down a voice call. Voice switching VoIP grew louder. Here, too, equipment manufacturers methods affect the speed, efficiency, and quality of voice are developing products to enable inexpensive, universal calls traveling through the network. Therefore, before voice over data networks. purchasing VFRADs, users must consider the voice Carriers, however, were caught in a dilemma. Could switching capabilities of each product, including ease of they afford to cannibalize their highly profitable public configuration, flexibility in dialing plans, quality of com- switched telephone network? Could they not afford to pressed voice, integrated fax support, and support for CHAPTER 3.2 Network infrastructure Frame Relay network Voice FRAD Voice FRAD Plain old telephone system (POTS) network Off-net voice Off-net voice user Figure 3.2-4 Example of VoFR. various physical interfaces and signaling methods. Before inherently less efficient than the circuit-switching explaining the importance of VoFR, it is necessary to network in dealing with voice. To achieve good voice desc