December 1998

Call Generators: CTI Takes A Test

BY BILL GUNNING

Central office and PBX telephone switch manufacturers typically rely on call generators to simulate a variety of operating conditions - the better to ensure that their products function correctly in all environments. Unfortunately, the same precaution is not always taken by vendors of enhanced CTI applications. The all-too-common results of inadequate application testing? CTI systems freeze-up, anticipated benefits never appear, revenue and productivity suffer, and customer service deteriorates. It comes down to this: No matter how well systems may operate on their own, and regardless of a vendor's claim about compatibility, unless complete systems are tested under real-life or simulated conditions, actual performance cannot be guaranteed.

Yet avoiding the above problems and ensuring that investments perform as expected is fairly simple. All CTI application buyers have to do is insist that the systems under consideration be tested completely in environments similar to their own. However, many CTI vendors contend that this is unnecessary because their applications rely on standard telephony interfaces - such as those from Dialogic and Natural MicroSystems - that have already been thoroughly tested.

THIS IS REAL LIFE
If a vendor takes this position, it should serve as a warning to an astute CTI shopper rather than a satisfactory response. Just because a telephony interface has been thoroughly tested, this does not necessarily mean that a complex CTI application running with this interface will perform as required. This can only be ensured by testing the CTI application itself, under load, and in an actual busy-hour calling scenario.

Developers and buyers of CTI applications need to understand that a complex application can significantly impact the way CTI platforms operate under a wide variety of call scenarios and transaction types. Each separate function in a voice mail system, for example, may work fine when tested independently. But when multiple functions are utilized simultaneously, as they are in real-life situations, the overall system may not respond appropriately and a variety of error conditions may be encountered: calls may be routed to the wrong extensions, unacceptable delays may occur, or wrong prompts may be launched. Since CTI applications tend to be business critical, it makes far more sense to test them with a call generator prior to deployment, rather than waiting to see what happens once the applications are live.

SIMULATION TESTING
With this in mind, there are several types of testing that a CTI product should go through before final deployment.

Conformance Testing
Call generators put the entire network through its paces by simulating actual user calls, including all possible interactions with the CTI application. This can only be done with call generators that are able to vary all parameters of DTMF dialing, including level, frequency, on-and-off timing, and twist.

In this way, all real calling scenarios can be simulated - even, for example, if calls are received from foreign countries where, rather than touchtone telephones, it is common to use hand-held DTMF dialers in conjunction with rotary dial phones. Equally important, the call generator must test all possible end user responses to prompts by simulating both the buttons callers would press and the different sequences in which they might press them.

Thorough testing also requires that the call generator be able to simulate different interfaces. In fact, in complex scenarios, multiple call generators may be needed for each separate interface that will be encountered (including analog, various types of ISDN, T1, and E1).

This type of call generation testing is called conformance testing. All the parameters evaluated during conformance testing should be reported on and carefully evaluated to determine any problems before the application is fully deployed. In fact, complete conformance test simulation of the actual workflow of a call - from the point that a caller attempts to reach the network, right through to the point where they get the information they need - is an invaluable first step in determining if the CTI system will meet a company's expectations.

Load Testing
The next step in evaluating a CTI application should be considering its performance during load testing. Similar to the basic load tests performed on telephone switches, CTI-oriented load tests must go one step further than standard switch tests. CTI load testing is done by simulating the parameters considered in the conformance tests, but testing under varying load conditions: from large numbers of short duration and simple calls, to long and complex call interactions. Such rigorous load tests fully exercise the system in real-world conditions, which is absolutely essential to ensure success when applications are brought live on the network.

Regression Testing
Conformance and load tests are critical when considering a new product. Another type of testing is equally important before committing to a new release of an existing product. This is called regression testing.

In regression testing, call generators are used to create a nominal amount of highly variable and complex traffic to simulate every possible path and decision a user could make. This test is run initially with the new release. Regression test parameters are then run against the original load test conditions - the previous version of the product - to ensure that the new release will yield predictable results in all scenarios.

For example, take the case of a new version of a CTI application that now includes support for international call back. Once tests are completed that verify how the new release performs, these tests need to be run again on the original product test bed to ensure backwards compatibility. Similarly, if a new version of an existing application adds new prompts for end-users, buyers of that new version need to completely understand how these new prompts will affect the application's overall performance. This includes accommodating, or allowing for in some capacity, the earlier prompts that end users are already accustomed to.

Taken in conjunction with conformance and load tests, complete reports from regression tests can provide valuable assistance to both vendors and users of CTI applications in determining how to resolve issues that may arise as they develop their CTI environment.

Acceptance Testing
There is still one final class of test that needs to be considered before making a commitment to a CTI solution: acceptance testing. Acceptance tests address the specific performance requirements checklist, agreed to by the vendor and purchaser, that stipulates exactly how the product should perform in the purchaser's specific environment. If specific signaling protocols must be supported, for example, this must be proved in an acceptance test.

The importance of acceptance testing cannot be overstated. It is also important to note that for a CTI implementation to be successful, it is the responsibility of the purchaser to provide the vendor with such a checklist, so the vendor can completely prove that the CTI application will meet expectations.

CALL TESTING EQUIPMENT
Where it is the responsibility of the buyer to provide a checklist for the vendor to complete, the vendor will generally be responsible for providing the appropriate call testing equipment. To facilitate the completion of all tests, call generators should be completely open so that the user can rely on either standard, or custom developed, protocol state machines for generating test signals. If custom protocols, such as those that might be common in a specific foreign country, must be tested, be sure the call generator system includes a development kit to streamline this task.

Actual testing of call flow also requires simulation scripts that specify the various actions a user would take when making a call. Two types of scripting capabilities should be offered by the call generation system: pre-programmed and custom. Custom scripts, most often required when tests are tailored to specific operating conditions, can be facilitated with a call generation solution that includes software tools that automate this task. Some call generators, for example, provide a full graphic scripting tool that requires no knowledge of programming whatsoever; by simply dragging and dropping icons and interconnecting them with mouse clicks, even complex scripts can be easily assembled.

Another important capability of call generators that must be considered by CTI vendors, and companies who rely on test results for evaluating products, is the size of application that can be evaluated. Call generators that include control tools are generally most effective for large test scenarios, since they allow multiple, distributed environments to be tested concurrently and effectively.

FINAL SUGGESTIONS
Call generation-based testing of CTI applications is an invaluable tool that all users of CTI systems should utilize if their investments are to be successful. In fact, we suggest that CTI purchasers insist that these tests be performed before they consider products from any vendor. Even large companies that may choose to do their own testing at a later date will benefit by dealing with vendors who have completely validated the performance of their products through call generation testing.

As CTI applications play an increasingly important role in the success of companies, and as these applications become increasingly complex, the importance of complete testing cannot be overstated. Today's CTI environments are used by more and more callers, and are interfacing with more and more networked applications. By extension, this means that the number of points of failure is skyrocketing. By validating CTI applications with thorough testing before deployment, unpleasant surprises can be avoided - and companies can be sure that they'll get what they pay for.

Bill Gunning is the senior vice president of corporate marketing for Ameritec Corporation. Ameritec is a leading manufacturer of test equipment for the telecommunications, data communications, and wireless markets. Ameritec supplies equipment to telecom equipment manufacturers, telephone service providers, and private businesses. For more information, please contact the company at 626-915-5441, or visit their Web site at www.ameritec.com.