[OpenSIPS-Users] Hold and Transfer from Mitel PBX drops call

[Paul Cupis]

Andrew Yager wrote:
> Our users on Mitel PBX systems can place and receive calls without a  
> problem. However, whenever they perform a mid call task, e.g., place  
> the call on hold or attempt to transfer, the call simply drops.

I've seen this on another platform. The problem was due to the Mitel 
using the late answer/offer model from RFC3264 which was not supported 
by our B2BUA. I think in the short term we resolved it by installing an 
InGate Siparator/Firewall on the customer site to do the inter-op.

Regards,