sundance-communications.com/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems Mitel EL PRI Errors

I recently replaced a PRI card in an EL. The old card protocol was set to DMS 100. I set the new one to the same. It worked for two months and then it started crashing. I was getting loss of sync errors and then the whole PRI would drop, alarm the system and then come back up again, only to drop out again. This went on for two days. The carrier (Windstream...need I say anything else?) insisted it was the Mitel and not ANYTHING with their PRI. Last night I went to the site, checked the PRI and everything was as I had originally programmed. I called Windstream's service desk (quit laughing) and finally got a switch tech on the line. It turns out their equipment, even though it is still a DMS switch, can't do DMS 100 protocol. So, it has to be NI-2.

OK, so I set the Mitel to NI-2. Now Windstream is telling me they are seeing CRV errors all day long. The PRI has stayed up with no errors reported in the Mitel for 24 hours.

Has anyone encountered CRV errors with a PRI on a Mitel? In case anyone was wondering, Call Record Values are located in the D channel and, from what I can tell, is ignored by the Mitel.

Rcaman

CRV or CRC?

Cylic Redundancy Check errors (CRC), if I'm not mistaken, typically mean a tiny amount of interference or resistance, and the resulting hiss/crackle is automatically removed by the fact that it's digital (the CODEC knows that .967 = 1, .002 = 0). Minor, minor physical layer issues.

In my experience, a CRC error is relatively benign so long as there are only a few here and there. If you're getting a blast of CRC errors and then the PRI drops, you've probably got a serious physical layer problem.

If the PRI is up and staying up, I'd just continue to monitor it.

Also, in my experience: CO guys very seldom know much about ISDN protocols. I've had them argue that there's no such thing as NI-2.

When the CO switchman said there were a lot of CRV errors, I had to look it up myself. CRC is something I know about and it is usually a function of improper protocol or something really off in programming. But, CRV is something that was new to me.

I dragged out my copy of the Belcore specs and did some "light reading." It turns out that CRV is a specification that is used by some switching COs to flag and track calls that set off a threshold alarm somewhere in the stream. I knew Mitel probably did not even deal with that portion of the data, but I looked into it just to be sure. The PRI has been running, without errors, in the Mitel for a week now.

What makes me laugh is the PRI is being served by a DMS switch and Windstream's switch people swear they can no longer emulate DMS protocol!! If the equipment can't emulate NI-2, then you are just not going to have service. This is just amazing to me.

Rcaman

In case anyone is interested, I finally tracked down the source of all the trouble with this PRI. It turns out the Adtran smart jack was bad. I changed out the one on the PRI with one I had and everything is working great. No errors of any kind. It took six hours of monitoring the PRI with my Fireberd, but I saw a recurring pattern which was not coming from the PBX but was appearing to the CO as data coming from the Mitel. This pattern would occur even when there was no traffic on the circuit. It would cause the channels to drop and then re-establish the link. The framing errors would pile up and the Mitel would report loss of sync. Rcaman

Thanks for the update