Behind-scenes testing keeps ISDN in line and running smoothly.

In a few days the era of National ISDN-1 will be with us. Special events are being held outside Washington, D.C., as part of TRIP '92 to mark the occasion.

TRIP '92 is the Transcontinental ISDN Project, a showcase for successful ISDN implementations. The North American ISDN Users Forum and the Corporation for Open Systems are cooperating to focus on ISDN and its real and potential applications.

National ISDN's first phase targets basic rate service, while next year's NI-2 will focus on primary rate. The NIU Forum is already seeking comments from users about planning for the next step, NI-3.

Behind the mid-month hoopla about the "arrival" of ISDN is a serious subject--testing--which makes sure equipment that purports to deliver NI-1 lives up to its promises.

Remember, NI-1 is quite a departure from the decade-long struggle to overcome incompatibility in switches and customer equipment. One big, happy, compatible ISDN is what everyone is after.

You can't guarantee this without some means of testing to see that equipment conforms to the standard and will operate with all other equipment. The good news is that users will not have to DO the testing--they're busy enough already--but they will benefit from it.

Equipment coming onto the market will be tested for conformance with the Bellcore NI-1 standard. Users shopping for ISDN-compatible equipment should make absolutely sure that it conforms. It's in their own interests, first to be sure they aren't caught with their compatibility down, and second, because if conforming equipment is what users demand, that's what vendors must and will supply.

Here's how conformance testing works: Now that the NI-1 protocol is fully defined, an abstract test suite is in place, specifying how to test a product for conformance. Product designers can test each protocol feature as they proceed through the design process and then test the entire product at the end.

Network managers can also do this type of testing on new network equipment they evaluate. Communications News' May issue profiled one manager who does that, though not with ISDN gear. Ron Szpak of the Bank of Montreal does extensive certification before allowing any new equipment on the network.

"Our customers can't tolerate network disruptions," was Szpak's rationale. Sound like your situation?

Hewlett-Packard, whose Idacom division makes the testing equipment used in such conformance tests, notes the issues that are resolved by NI-1 and those that aren't. On the resolved side, for instance, are these issues:

* Information elements at Layer 3. They will be interpreted the same way by all pieces of ISDN equipment.

* Customer premises equipment. CPE, ranging from telephone sets to data gear, will be usable with any ISDN switch without compatibility problems.

* A single ISDN version allows for more intelligent automated troubleshooting. What ISDN has done for a long time has been to present a real challenge to test equipment. It has been tough to follow the protocol and locate errors since each version of ISDN operated a little differently from the others.

The issues that NI-1 won't resolve are:

* Physical layer problems, a common woe when it comes to any technology. These are likely to occur especially as companies try to condition their old telephone wiring to support ISDN.

* Configuration problems. These usually result from a switch not being translated for a feature subscribed to by the user.