A fault tolerant VoIP implementation based on open standards

Abstract

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