[ian_news]

Using a Sipura-2100, firmware 3.1.2b

All parameters are as out-of-the-box, except the registration interval (reduced from 3600 to 60 seconds).

Most of the time everything works fine, but sometimes, at a certain time in the morning (around 7 o'clock), the ATA stops receiving registration acknowledgements from the VoIP provider (Voipfone). After about 15 minutes without receiving acknowledgements the ATA stops trying to register, and goes to sleep for 20 minutes. It then wakes up, tries again to register, and is successful.

I am now in the process of trying to track down where the problem is occurring -- is it in the ATA, or in the broadband network (NTL), or at the VoIP provider?

However, as a side issue, when tracing the registration traffic between the ATA and the provider, I've noticed something strange happening. Each minute, the ATA sends a REGISTER request, but the provider always rejects it. The ATA then immediately sends a second REGISTER request, and this time the provider always accepts it. The only significant difference I can see in the payload of the two requests is a difference in the "branch" string. The first "branch" is obviously wrong, and the second is right.

So, my question is -- what is the "branch" string, what sets it up, why does the ATA get it wrong the first time, and how does it get it right the second time?

--
Ian