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Mind Share

August 1999

Marc Robins Pain-Free Internet Telephony-Powered CT-Apps

An Up Close And Personal Look At Dialogic's Empowering "Thin Gatekeeper" CT Connect Extension


During a recent trip to Dialogic Corporation, a leading manufacturer of CTI and Internet telephony board products and enabling technology, I had the pleasure to meet a number of key company movers and shakers, including James Machi, the Director of Marketing for the IP Telephony Division, Greg Baltzer, VP of the Telco Network Services Division, and Carl Strathmeyer, Dialogic’s Director of Marketing for the company’s CT Connect, or Computer-Telephone Division.

During the meeting, we were brought up to date on the company’s DM3 IPLink IP telephony platform product, CT Media, and CT Connect product plans and strategies. The day was chock full of interesting information (including the “small matter” of Intel’s purchase of Dialogic, which made the wire while I was en-route to the meeting)!

But perhaps the most eye-opening (and to a CTI application developer, exhilarating) bit of news came to light during Carl Strathmeyer’s fascinating demonstration of a new “thin gatekeeper” component of CT Connect.

First, A Brief History
For those of you who are unfamiliar with CT Connect, it is a “middleware” product that supplies the communication path between a telephone switch and CTI applications. CT Connect, which is based on the CIT (computer-integrated telephony) technology acquired from Digital Equipment Corporation, was released in August 1995. It is designed for use by application developers, VARs, and OEMs to construct end-user CTI solutions.

The new CT Connect version 3.0 is capable of connecting a wide range of telephone switches to a variety of data processing environments. The CT Connect client/server software technology supports industry-standard hardware, operating systems, network services, and call control programming interfaces such as TAPI, TSAPI, ActiveX, and DDE. CT Connect consists of server software that runs under either Microsoft Windows NT or Sun Solaris operating system environments and supports comprehensive call control and monitoring through links to many popular telephone switches.

The server software implements the necessary communication protocols to work with each switch’s computer telephone integration (CTI) link, maps the differing protocols and messages to a common CSTA-based call and information model, and manages the flow of telephony service requests and status messages between the server and multiple concurrent application systems. CT Connect provides OEMs, application developers, and integrators with the ability to implement complete telephony routing and monitoring functions inside their applications.

On To The Gatekeeper
In a nutshell, this new gatekeeper component — essentially a “bare bones” gatekeeper without policy logic and QoS functions — coordinates CSTA messages generated by CT-Connect to analogous H.323 control codes, in effect serving as a “turnkey,” standard interface between Internet telephony and CTI applications.

According to Carl, current industry thinking is that gatekeeper-resident logic should implement the various desired call-flow policies. He believes this approach will inevitably lead to expensive, complex, and inflexible gatekeeper feature implementations, since gatekeeper environments are not easy ones for CTI developers to work in.

Dialogic’s approach is instead to provide a CTI linkage out of a fixed, basic-function gatekeeper module, so that external CTI-style applications can implement the policy logic. Since this arrangement can handle multiple external CTI applications, and since those applications can be implemented on any convenient system platform, the company believes this approach will result in lower costs and more flexibility for IP telephony call processing.

The company’s new gatekeeper module helps extend the capabilities of CT Connect by allowing CTI applications to monitor and control Internet telephony calls in the same way they currently do in traditional telephone environments — and, in essence, enabling third-party call control for Internet telephony. Dialogic’s view is that third-party CTI capabilities are vitally important to commercial, enterprise use of H.323 telephony, just as CTI concepts are now essential to the operation of any traditional telephony call center. I completely concur.

Look Ma — No Code Changes
This new CT Connect component is almost the “holy IP grail” for the ever-growing army of CTI application developers trying to sell their products into a marketplace that is rapidly adopting IP-centric technology. By employing this “thin gatekeeper” in conjunction with CT Connect, CTI applications will be able to operate within IP telephony environments as easily as in a circuit-switched telephony environment. The transparency it creates between IP telephony and traditional phone switches means that CTI developers will be able to market their applications for use in IP telephony environments — with little or no change to existing code. This has got to make a developer’s face break out into a broad smile.

For the end user of an Internet telephony-enabled CTI app, there are also tantalizing possibilities — customers will be able to use IP telephony in conjunction with contact management, customer service, and support applications, deriving all sorts of cost savings as a result.

Dialogic has filed for a patent for their thin gatekeeper, and expects to offer it as a CT-Connect component by the end of the year. The company is also interested in working with providers of gatekeeper products and operators of public IP telephony networks to help incorporate this important CTI interconnection technology into their offerings. If you’re one of these folks, contact Carl Strathmeyer at 978-275-4802 or e-mail him at [email protected].

Marc Robins is Associate Group Publisher for INTERNET TELEPHONY AND CTI magazines. His column, Mind Share, appears monthly in the pages of INTERNET TELEPHONY magazine. Marc looks forward to your feedback.


The demonstration shows how H.323 calls can be supervised by a CTI application in the same way that calls through a PBX can be supervised. The left side of the diagram shows the traditional telephony portion of the demo: A standard analog telephone connected to a PBX, which is in turn connected to an H.323 gateway that converts the traditional telephone call to a packet telephony call. The gateway in this demonstration is constructed using a Dialogic D/41 board for the traditional telephony interface, a Dialogic DM3 IPLink board for the packet telephony interface, and a simple gateway application that is part of the IPLink software development kit (SDK). The two boards are interconnected with a standard H.100 TDM bus.

For the softphone endpoints on the right side of the diagram, we used Intel’s VideoPhone application. Dialogic has also tested the new V3 beta kit for Microsoft NetMeeting with this demonstration with good results. (Previous versions of NetMeeting were not compatible with the Gatekeeper.)

The Dialogic prototype CSTA-enabled gatekeeper is shown in the upper portion of the diagram. As specified by the H.323 protocol, all endpoints, including the gateway, detect and register with the gatekeeper. All call signaling between those endpoints then flows through the gatekeeper as calls are set up, rerouted, and disconnected. The gatekeeper communicates all important call state changes to the external application environment via the appropriate CSTA messages. External applications can also send requests to the gatekeeper to request that the gatekeeper take actions on calls.

Dialogic’s CT Connect CTI gateway provides the communication path between all external applications and the gatekeeper, translating the CSTA messages used by the gatekeeper into the appropriate telephony API as used by each application.

In this demonstration, the application is built within Microsoft Access. The application has a table of customer contacts, and provides preview dialing and screen pop functions for that table. The application uses the CT Connect ActiveX control, which can be easily embedded into an Access form. (This application is the same application used to control calls in a PBX environment.)

If the user places a call from a traditional telephone or an H.323 softphone to another H.323 softphone, the Access application associated with the destination softphone will receive call progress events via the gatekeeper, CT Connect, and the CT Connect ActiveX control embedded in the application. The application then executes a screen pop based on the calling party telephone number.

The user of one of the softphones can also select a contact record and press the application’s DIAL button. This causes a dialing command to be passed from the ActiveX control to CT Connect and then to the gatekeeper. The gatekeeper establishes one leg of the call back to the calling softphone and then a second leg of the call to the selected destination — either another softphone or a traditional telephone via the gateway.

This demonstration shows that calls in a packet telephony environment can be supervised by a CTI application just like calls in a traditional telephone environment, and that the application does not have to be modified to accomplish this. This means, in turn, that the growing library of CTI applications available for traditional telephone environments can be applied to packet telephony environments, speeding the adoption of the technology and improving the business case for application developers

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