atcomsystems.ca/forum Forums TDM Business Telephone Systems Nortel Telephones & Systems MICS 6.1 Dropping T1 Calls

I have a customer running a MICS w/6.1 Software.
There are two DTI PRI cards installed. One PRI is a local T1 and the other is a Long Distance T1. The T1s use routing to determine which calls go out on each t1.

The problem is that the system is randomly dropping calls that appear to be longer than 20-Minutes in duration. It may drop the call after 22-minutes or after 31-minutes. It does not drop every call just about 1 out of 10.

The Local PRI T1 (Telepacific) is set as the Primary Clock Source with NI Protocol while the Long Distance T1 (Qwest) is set as Secondary with DMS100 Protocol.

What could cause this? It doesn't appear to be a Carrier Problem and I don't think both DTI cards are goofy.

You have 2 different carriers?

And this problems is occurring on both spans?

How long in service before this started happening?

Is your 6.1 software the Maintenance Release (MR) version? And do you have a T1 or PRI, there were issues with pre 6.1 MR software and PRI's.

Why don't you set up both T1s as NI2?
Besides,you might have a problems with COMBO module loosing sinchronization.

The MICS Version Level is "SP: 30CQE06 NAT".

It appears customer has received recent "Alarm: 44-0". The carrier has recently changed over circuits and I think that is when the dropped call problem started.

I am going to switch the Primary Clock Source to the LD T1 to see if it is a clocking issue.

I have yet to experience a T-1 issue that has turned out to be the MICS system, once it was up and running. Every complaint about dropped calls, can't call out, etc has turned out to be Telco so far.....knock on wood!

It appears after talking to both the Local PRI carrier and the Long Distance carrier that when mixing two or more T-1s it is best to make the Long Distance carrier the Primary Clock source because the local carrier usually has to sync with the LEC (if different) and can cause frame slippage problems which I think my customer was
getting.

Since making the Long Distance carrier the Primary Clock source (local is secondary) the customer has not dropped any more calls. Also the MICS was pretty good about reporting an alarm (e.g., Alarm: 44-0) when the T-1 experienced a dropped call.

Another thing I have to remember is when changing T1 settings on the MICS it is best to reboot the MICS after all changes have been made. After I made T1 settings changes the PBX was acting very strange until we finally rebooted system and then everything was working great.

Thanks for the update.