Single Channel Down on PRI

[IntermixMatt]

Yesterday, one of my customers reported a partial service outage. They were unable to call out to local numbers. They could reach long distance numbers (separate circuit) and could receive all incoming calls. I reported this issue to the carrier and they responded a short while later stating that a single channel had gone down on one of our PRIs. To remedy the problem they "switched it to the b-side". I was under the impression that a PRI was all-up or all-down. My understanding of the technology is limited, but am I correct in assuming that what the technician told me is not possible?

 

[trvlr1]

It is possible that one channel can go down and be unuseable. However, it is very strange that it is blocking calls, unless that is the only outbound channel, or somehow your configuration or the Telco's configuration, is not set correctly.
You did not say what kind of phone equipment you are using. If you give us that information, someone with knowledge of it may be able to point you in the right direction.
Also, what was the result of the failed outbound call, did you get a message, busy signal, silence .....?

 

[IntermixMatt]

They have a Mitel 3300 MXe. The customer reported a busy signal (could've been a fast busy) on local outbound calls.

 

[trvlr1]

You might want to try posting in the Mitel Network Solutions area, there will be a lot more experts on this type of equipment there i am sure.

 

[donb01]

I have had this happen with AT&T. It only LOOKS like one channel is down, but in reality the whole span is not taking traffic. If you shut the circuit down and restart it in your system all of the channels will go down and not come back up. I have gone around and around with the service center until I found a helpful tech that "bumped" (deactivated/activated) the circuit from their end, and everything popped right back up without any further touching by me. I now have the phone number that goes directly to the helpful tech's work group, and they all know what bumping the circuit is. I have had this happen twice since out of my 7 sites, and I can now quickly have the problem corrected.

Of course your problem might be from something different, but that's what it has been for me, and it always starts with a single channel appearing to be down.

 

[IntermixMatt]

donb01, when that happens, are you able to make outgoing calls on that circuit? Also, is "bumping" what the technician meant when he said he "switched it to the b-side"? Thanks for the information.

 

[donb01]

All incoming calls on that span typically will get fast busy, and nothing goes out. I have 3 spans, and they are programmed top down for incoming and bottom up for outgoing so it has to get pretty busy if I'm lucky enough to have an issue on the middle span. If the first or last one goes down they are usually screaming the moment it happens.

My understanding of what he meant by "bump" is that he did the equivalent of deactivating the circuit in their switch, giving it 30 seconds or so to stabilize and then reactivating it. Generally as soon as that happens in my case I will either see everything come back up, or I just need to drop the D channel and bring it back up, and then everything else will follow.

 

[kwbMitel]

It is very possible for 1 channel to be out of service.

The most likely scenario is that the when that channel was selected, the call would fail. (maybe the 3rd or 4th line out for example)

Additionally as the majority of calls are local, it makes sense that local calls were affected but this would only be a coincedence.

re:"Switching to the b-side", as a Mitel tech, I can only guess there's a loss of communication here.
- Each channel is referred to as a B-Channel.
- On a Mitel SX-2000 you would possibly have a A-Plane and B-Plane (redundancy) thus you could switch to the B-Side but this would not affect the PRI unless it was reset.
- A typical fix is to Busy out the channel and restore to service but Switching to b-side is a stretch there.

Come on over to the Mitel forum, there's lots of us ready and willing to help

http://www.tek-tips.com/threadminder.cfm?pid=1329

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