VToA has been written and talked about since the introduction of fast-packet switching concepts and the beginnings of the ATM/synchronous optical network (SONET) standards, which occurred during the mid-1980s. What differentiates VToA from a private line enterprise application is service-level interworking with the public switched telephone network (PSTN). Although a number of product vendors have committed to deliver certain VToA components, only one has a revenue-producing intelligent network (IN) application in place that manages, bills, and controls residential and business telephone calls over a public ATM–switched, digital broadband integrated services digital network (BISDN).

The evolution of the IN experienced a profound change in direction early in 1995. A number of vendors began the development of operations support systems (OSSs), service management systems (SMSs), and IN applications for the then infant ATM switching and SONET transport technologies. The common service wisdom seemed obvious—build another cost-plus, private-line overlay network for high-speed data services using edge switches that are connected to customers' routers and local-area networks (LANs) for each enterprise network. The SONET–deployment strategies were just as simplistic—install high-speed optical rings, interconnected with automated patch panels that could cross-connect the fixed-speed private lines.

Market demand, competition, and advances in technology rejected the prevailing cost-plus carrier mindset and simplistic overlay-implementation plans. Engineers, designers, and network planners saw that the power and promise of ATM/SONET standards and the resultant technology was clearly a single integrated infrastructure, able to manage and deliver all subscriber signals (audio, data, voice, and video) reliably and efficiently. This package of switched and dedicated services on a single, integrated network became known as VToA.