sundance-communications.com/forum Forums General General Telephone & Systems Information SBC/ATT PRI Failure Secondary Rerouting

depending on how your reroute is setup the secondary route will normally not reroute unless it sees the trunks down. If the t failed but the trunks stayed up in the switch(due to a loop or something along that route) then no reroute, when you unplug the t from the rj you lose your d-chan sync which in turn fails the trunks. If the switch saw your trunks in service but they were actualy dead, the call would have been sent down the pipe instead of rerouting to the secondary route, when it did not get any respose from the cpe it would respond with a network not in service msg.

Thanks , anthonyh
That may have been the issue . That helps to explain the OOS/NIS recording the callers where receiving .

I am sorry justbill I forgot to thank you also . Just color me brain dead sometimes . Thank You justbill for your help . SBC/ATT and us are going to to recreate the failure this Thursday at 2am and see where the hicup was/is . I will just have to reinstall the defective power supply . Thanks again .

I'd be curious to know what SBC showed as the condition of the primary trunks at the time of the failure. They should be able to check the switch logging and get this information. That could help explain why the route advance didn't work. It's obvious that if the callers were getting the OOS announcement, the trunks were truly down. The alternate routing was translated correctly in the local switch because calls completed once you opened the circuits at the jack. My guess is that the power supply failing left the trunks in an abnormal state. You may not be able to reproduce the problem even by replacing the power supply since the situation will not be the same. Please post what you find out on Thursday morning.

The problem was with the way SBC/ATT had the alternative rerouting programmed . What exactly they changed I could not get out of them . Works now so I guess that all that matters . Now if only they can fix my level 2 resets on 2 ptp t1's terminating on our local pbx . Luckily the 3rd one is still working . But since I have the other 2 busied out we are having congestion problems . If it ain't one thing it's another . :shrug:

Ok here is what I think happened. PRI (Primary Rate ISDN) is a feature that rides on a T1 line. T1 was first developed for CO to CO interconnection. DS1 (that’s the signal portion of a T1) has a framing bit that the receiving end uses to know which bits makeup the 24 channels of a conventional DS1. The old programming for CO to CO interoffice trunks, was that if the CO did not receive the DS1 signal the CO equipment would “loose frame sync”. With lose of frame the CO would block calls to those 24 trunks. PRI uses the 24th channel of the DS1 as the D (data) channel for ISDN. If you loop a PRI T1 back to the CO, DS1 framing will be maintained. With a looped DS1, none of the channels including the D channel works. I think your provider had the office programmed to alternate route if the DS1s were out of frame sync and not of the D channel was out of service.

Have you ever had a Flat and then found that the spare does not fit the car it’s in? It may be a good practice on new installs were you are purchasing alt rerouting to loop the PRI T1 back to the CO and see if it alternate reroutes.

Yep
It should have been tested for alt reroute when first turned up . Why it was not is anyones guess . It is SOP now . Thanks