Errors on T1 D-Channel

[CiscoWizard]

If this doesn't go here, I apologize. I didn't see a spot for general networking topics.

We have some antiquated equipment where I work. This is the second time that errors were accumulating on a circuit, but not impeding data flow. The errors are on the D-channel of the T1. I know this is a control channel so it doesn't have much of an effect on how data flows. We're being told it is coming from our equipment, which is a GDC 701 CSU/DSU. To me, if it's an issue with the control frame that it would have possibly come from a software configuration issue or possibly the channel bank. I don't believe that errors from our equipment would strictly effect  the D-Channel alone but I can't be 100% sure.

Does anyone here know more about the issues caused by a T1 D-Channel?

[deanwebb]

Is it possible you're headed for hardware failure? Are you able to run diagnostics on your unit?

[Otanx]

The D channel is as you say the control channel. Issues with it may impact data flow as it is used for issuing commands between the devices. I believe the timing for the B channels is also done over the D channel, but I have not touched ISDN/T1 in a long long time. You don't say specifically what the issue is, what kind of errors are you seeing? Just BER incrementing? If you only see them on the D channel then I would guess a device failure of some kind. The B channels are running at higher rates, and typically you would see bit errors on those if there were line issues. I would try swapping with a spare, and see if the problem goes away. If you don't have a spare then this is the time to start looking for one.

-Otanx

[CiscoWizard]

We have limited responsibility for the length of the circuit. In the photo I attached we are only responsible for the C/DSUs. The circuit run and other hardware belongs to different groups. Our equipment was checked and replaced but the issue persisted.

I wasn't told what the exact errors were. I kept hearing them say they were "locked out of the D-channel" and that's where the errors are. Yesterday a couple of the groups worked together and proved the circuit run, both copper and fiber, tested good. It looks like the issue is with the equipment in the PBX but we keep getting pushback from that group. People here have trouble admitting their stuff is malfunctioning. They act as if it's a slight on themselves.

[deanwebb]

The PBX folks need to come clean and you are right to press for the exact error messages. Specific words help in searching for the right resolutions, and they need to respect that.

[CiscoWizard]

Thanks for the assistance. It looks like the BER errors were only on the D channel. They're going to dispatch someone today to check their equipment.