Orbtalk have a range of SIP trunk products that work with the Avaya Communication Manager
Communication Manager software provides call processing solutions for large and small customer environments. Communication Manager is an open, scalable, highly reliable and secure telephony application. Communication Manager provides user and system-management functionality, intelligent call routing, application integration and extensibility, and enterprise communications networking. The standards-based Communication Manager also uses H.248 for gateway control. Communication Manager offers over 500 features, in the following categories:
Call centre
Telephony
Localization
Collaboration