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Class 5 PRI Protocol Testing

For the NI-2 PRI software I was assigned to verify, rule of thumb estimates had already been delivered of two weeks testing. The reason being considerable overlap existed between NI-2 PRI and other PRI variants we already claimed support for such as ATT 5ESS and Nortel's DMS100 central offices.

After familiarizing myself with the requirements and design specifications, I identified over 300 unique internally generated requirements for which no existing test cases or test scripts existed. Unlike the ATT 4ESS PRI where the test specification was published by the testing authority, There was no publicly available test specification for class 5 PRI's. Bellcore did not publish their specification and it was known to be quite rigorous.

The schedule implications of having to write and debug over 300 scripts caused numerous meetings. A decision was finally made that I and a co-op student would work together to test the feature. We were given a dedicated switch and dedicated protocol analyzers.

As was the case in the prior release when verifying the ATT 4ESS PRI software, a complete suite of class 5 PRI scripts were not available for our existing vendor specific code. Work would have to begin largely from scratch and was further expanded to include a regression suite of scripts for the older vendor specific PRI code.

We wrote scripts, debugged and executed them. In the process, a lot of defects were identified, many extending all the way down to the original code base. We put in long nights and weekends to get the work done and testing was completed well within the overall project window.

Part of the overall test strategy was that as testing progressed, the switch database to be used for Bellcore conformance testing would also be created. This database could then be reused in the future rather than having to start from scratch building a switch and database as we were doing. In the future, all that would be needed was to begin with an empty switch, insert line and trunk cards in the correct slots per the map we provided, load the software, install the database, restart the system and viola! Only a few hours would be required to do what might require an experienced engineer a week or more to provision.

Once in-house testing was complete, the PBX was completely ready for Bellcore testing. All that was needed was to have it packed and shipped to the Bellcore test lab. The co-op and I were then assigned to assist in the testing of other features until the time came to travel to New Jersey for compliance testing.

Upon completion of compliance testing at the Bellcore lab in Red Bank, NJ, the Bellcore staff congratulated our product as being the only ISDN product they ever tested that successfully passed all tests on the first attempt.

Shortly after completing the testing, I accepted an offer with Nortel in Raleigh, NC working on the DMS10 central office. I took the offer with mixed emotions. On one hand, I had an opportunity to greatly expand my knowledge of telecommunications by moving into public switching where I could learn about central offices and SS7. On the other hand, leaving so many good friends and good memories acquired at Siemens was a very difficult thing to do.

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