We suddenly encounter 403 forbidden errors on outgoing (and potentially incoming calls). When I called our service provider (Broadvoice/PhonePower), they found that our system is no longer sending keep alive requests. I believe this problem has started with the recent upgrade to 15.5.9348.3 (Linux). When I checked the trunk configuration, I was surprised to see that it doesn't even have an option to configure a keep alive value (e.g. 60 seconds). Basically, the registration with the provider eventually fails resulting in us no longer being able to make phone calls (or receive calls). Does anybody have the same problem? Any solution?