January 1999

VoIP: Evolution By Design

BY WILLIAM H. MATLACK, JR.

In addition to its role as a low-cost global voice switching fabric, VoIP technology is evolving to offer call control functionality and integration of voice, services, and data that equals or surpasses that available on traditional voice networking platforms. As an alternative telephony switching fabric, VoIP takes advantage of economies of scale associated with the unification of voice and data services. But its full potential, both within corporate and public networks, will be realized with the addition of call control features now standard on PBXs and ACDs and with new applications taking advantage of CTI and media services interfaces.

Adding call control services to VoIP involves support for such functions as the delivery of call associated information (such as ANI, which can be used for screen-pop and call routing); hunt group, pick group, and ACD group functionality; call routing and queuing; multi-party calls; deflecting and transferring calls; and such features as call forwarding, Do Not Disturb, and call blocking. Products offering a complete complement of call control features on a VoIP switching fabric have the potential to compete with traditional PBX and ACD products. The development of such VoIP implementations is driven by the fact that they can offer the functionality expected of telephony systems while consolidating the planning, implementation, and maintenance of voice and data networks, ranging from small LANs to IP networks operating on a global basis.

An advantage of VoIP is that it permits a seamless scaling of network services with little extra cost because it can take advantage of the universality of IP networking, in contrast to traditional voice networks, which require an independent cabling and equipment infrastructure. Adding call control functionality to VoIP implementations, resulting in "IP-PBXs," will open the door to a new generation of computer telephony applications that integrate the functionality of the voice network with a wide variety of applications running across the data and computing infrastructure of the same IP networks.

AN ARCHITECTURAL MODEL
With this in mind, the Enterprise Computer Telephony Forum (ECTF) has defined an architectural model for computer telephony. This model provides for computer telephony servers distributed throughout an IP network, where each server may offer a CTI and/or a media services interface, providing access to call control functionality and manipulation of telephony media streams respectively. CTI services allow application software anywhere on the network to manage voice calls. Media services allow application software to access media streams in order to play and record audio, convert text to speech, send and receive faxes, and more.

For example, application software in such an environment can implement an integrated voice response (IVR) system, an automated attendant to route calls, or a unified messaging service. The opportunities afforded by such a network are limited only by our imaginations. Application software running anywhere on the network could route voice calls based on an individual's location, as determined by where they are using data services on the network.

In one possible scenario, an important call could be deflected to a software agent when it is determined that the intended recipient is on the phone. The agent software, acting on behalf of the busy party, uses the facilities available in a media server to capture information from the caller. An icon might pop up on the recipient's screen with information about the call. The recipient could then choose from several delivery options: conclude the present call and take the new one, or have the agent record a voice mail message to be delivered to an e-mail box. The latter choice could include converting the voice message to a text file using automatic speech recognition (ASR) technology and delivering it as a pager message or fax.

Another illustration of the powerful call control capabilities in VoIP networks is seen in the support for full voice and data collaboration on documents and presentations. For example, a group of people could be collectively reviewing an electronic presentation in a voice conference call over VoIP while viewing and modifying the presentation on their screens. The entire session would be established and managed using CTI applications and would occur over VoIP at a fraction of the cost of a long-distance PSTN conference call.

SUPPORTING THE EVOLUTION OF VoIP
If this vision of CTI applications on VoIP is to become a reality, it will require that software and hardware products from diverse vendors reflect all of the functionality offered by existing telephone systems, and that these products be easily integrated with one another and with the installed base of PBXs and PSTN services. Products will be successful only to the degree that sufficient interoperability can be established.

The ECTF publishes interoperability agreements for use by vendors of telephony products to ensure that their products will meet these requirements. C.001, a part of the CT architecture defined by the ECTF, describes the model for call control services. Its in-depth descriptions of call control features and services are playing an important role in the implementation of products that deliver call control for VoIP. Developers of these products face two significant challenges: they must simultaneously deliver call control features competitive with existing implementations, and they must expose these call control services through all of the popular CTI interfaces. C.001 addresses both of these challenges by defining a complete call control model that represents a superset of mainstream PBX and ACD functions and that is designed to work with all CTI APIs and protocols.

Developers using C.001 as the basis for their products don't have to re-invent call control functionality or fear overlooking a key feature. Furthermore, by basing their implementation on C.001, developers are able to implement support for CTI protocols and APIs such as JTAPI, TAPI, and TSAPI with minimum expense. C.001 provides a stable, comprehensive model with consistent behavior that allows easy mapping into multiple APIs and allows application portability between different call control implementations.

When applied to VoIP, C.001 saves vendors from the hassle of inventing their own proprietary call control models or having to rework applications due to oversights, and it will allow applications to interoperate with other call control implementations. In addition to making it easier to implement call control applications over VoIP, C.001 will simplify the support of CTI and media service applications.

Other ECTF specifications - including S.100 and S.200, which provide access to media services, and H.100 and H.110, which define bus architectures for modular computer telephony servers - are also at the heart of modular VoIP solutions. Last spring, the ECTF announced that it was committing technical resources to addressing additional interoperability issues related to CT/Web/IN convergence. The ECTF is currently working directly with the Intelligent Network Forum (INF) to develop implementation agreements that will provide even more guidance for product vendors seeking to bridge VoIP networks and the PSTN.

The promise of global accessibility of both voice and data at very low costs is generating a market demand for this capability. Predictions vary on how long it will take for the full integration to occur, but the ECTF architecture, with its ability to model applications and media services, will make it a much shorter process.

William H. Matlack Jr. is a freelance writer and public relations specialist in the San Francisco Bay area. He can be reached for comment at wmatlack@msn.com. The Enterprise Computer Telephony Forum facilitates the development, implementation, and acceptance of computer telephony solutions by bringing together suppliers, developers, systems integrators, and users. For more information, visit their Web site at www.ectf.org.