This is a upcoming problem that we are experiencing in Northern California on new build outs of DS3’s. We have experienced it to date 4 times.   Each time the LEC engineer is surprised.  It is not a problem with AT&T or any other carrier directly, but it does require the LEC to resolve the issue.

This was orginally experienced on a Verizon Business DS3 using AT&T as the LEC.  Verizon Business was very persistent.  They were well aware and acknowledged there was an issue but admittedly did not know what it was.  We worked with 3 engineers at Verizon Business simultaneously.   AT&T was difficult.  The third engineer we dispatched was great and was willing to work through the problem.  Persistence pays off.

When we ran to loops provided by the LEC at the MUX, all was Clean.  When we placed a Hard Loop on the Adtran DS3 NIU, all was clean. When we connected to the router we took errors.  Placing a Hard loop on the Router, all was clean. The router was a Cisco 7206 VXR with a PA-T3.  The distance from the NIU and the router was about 20 Feet.  Replacing the DS3 cables 3x did not change the issue.  Changing all of the settings in the router ( Encapsulation Protocol, Line Build Out, Clocking, Scramble. Etc…) did not resolve the issue.

Resolve:
After multiple dispatches we had an AT&T engineer on site.  He pulled the NIU card and all of the errors went away.  The AT&T engineer replaced the card with a new card and the errors returned.  I had heard of Line Build Out (LBO) being an issue, but ran into it usually if the cable run was too long.  I asked the AT&T Engineer to look at it.  He stated there was no option on the MUX but he could look at the NIU. The NIU was software configurable with a serial connection.  There were two options.  Normal and Short.  Default is set to Normal. We set the NIU to short and all of the errors went away.