A fault tolerant VoIP implementation based on open standards

This paper highlights the design and implementation aspects for making voice over IP softswitches more dependable on commercial of-the-shelf telecommunication platforms. As a proof-of-concept, the open source Asterisk Private Branch Exchange application was made fault tolerant by using high availability middleware based on the Service Availability Forum´s application interface specifications (AIS). The prototype was implemented on Intel x86 architecture blade servers running Carrier Grade Linux in an active/hot-standby configuration. Primarily, the Asterisk application was re-engineered and adapted to use AIS defined interfaces and model. In case of application, component or node failures, the middleware detects and triggers the application failover to the hot-standby node. The Asterisk application on the hot-standby node detects it is now the active instance, so it retrieves the checkpoint data and immediately continues to service both existing and new call-sessions thus improving overall availability