The telecom industry has gravitated toward an IP multimedia subsystem architecture in part because of its ability to deliver services over multiple types of access networks, enabling convergence. The problem has been that IMS, like any ambitious network change, isn't happening fast enough for everyone. AppTrigger is capitalizing on the need to offer services that look the same over multiple access networks today, instead of waiting for IMS. At the same time, the 5-year-old venture-backed company, is promising that its technology will bridge the gap to IMS and prepare service providers for that transition.

In order to do this, AppTrigger has created what it calls a new network element: the Application Session Controller (ASC). The ASC is a software-based solution that sits between the network and applications and provides a layer of abstraction, enabling one application to deliver a similar user experience to multiple types of access networks.

Existing applications have been developed for single networks — wireline, wireless or data — and have incorporated the protocols, interfaces and signaling of those individual networks. In some cases, there are even multiple variants of those protocols that are geographically based or company-specific, said Patrick Fitzgerald, vice president of marketing for AppTrigger.

“The challenge to doing cross-network converged applications is enormous,” he said.

To meet that challenge, the ASC provides all of the network interfaces — including session initiation protocol and the many SS7 variants as well as interfaces to Class 4/5 switches. On the application-facing side, it has a series of open application programming interfaces (APIs), including Parlay, XML and others.

“We want to be agnostic about the API,” Fitzgerald said. “Different ones are used by different communities of developers for different reasons. We don't necessarily have a position on which API is better.”

The ASC will provide media and signaling system functions to convert to and from bearer traffic formats and provide basic functions such as detecting and generating DTMF tones, playing and recording announcements and conferencing. It also has a call control subsystem that includes a call model in which applications can intervene to enable service delivery. The two function together to provide an abstracted view of the network that enables applications to function, regardless of the underlying network.

The ASC embeds network protocols into each application solution so that the application is optimized for the appropriate networks. “It provides traffic signaling and feature transparency between networks,” Fitzgerald said. “It provides call control independent of the underlying network. Today, call control has to be written into the application or obtained from the network.”

And when IMS does develop, he said, AppTrigger's ASC will migrate into that network as well.