Avaya G3 dropping calls after 20 seconds

[techalum]

Hello everyone!
I really need your help with my problem. I have two G3 systems that are causing me a headache. We are doing office to office dialing (5 digit dialing) from the US to the UK. The calls between the offices sometimes drop after about 20 seconds. At times, it will happen multiple times in a row. Other times the call may drop at the 20 minute mark. Furthermore, it will sometimes go days without any kind of problem.
We have captured packets and see frame errors between the two sites. The first ting I did was change the ports on the switch to verify that they were not faulty. Everything checked out ok. The second test involved calling from the UK to Switzerland as well as US to Switzerland. Switzerland uses an IP Office system. Although we still saw some LOF errors, the call never dropped. We let the call stay up for several hours. Has anyone run into this issue? Other offices that have an IP Office system can make calls to the UK and the US without experiencing any problems. Avaya phone support took a look at the system and could not find any issues. My telecom engineer has years of experience and is stumped by it as well.
If anyone has any knowledge of this type of error, I would appreciate it if your thoughts could be shared.

Thanks!
techalum

 

[cjinsocal581]

TONS of questions first:

What versions are these systems running?
Is this a MPLS network?
Size of the pipe between the sites?
Does it have sufficient GOLD CAR? (Committed access rate)
Phone types? IF IP, what firmware are they running?
Have you run a list trace on the G3 (CM) side?
Have you run a monitor trace on the IP Office side?

Lots of variables here. But sounds like you have issues where voice is not getting priority and those packets will be dropped by the provider.

Cheers,
CJ