Efficient, scalable migration of IP telephony calls for enhanced fault-tolerance

IP telephony or VoIP has seen tremendous growth in the past few years and is predicted to grow rapidly in the coming years. Hence, IP telephony components must provide service with high-availability, comparable to traditional telephony systems. In this paper, we present an efficient and scalable fault-tolerance mechanism for migrating calls to an alternate IP telephony call controller in the event of the failure of the call controller or network connectivity to it. We also present an efficient algorithm for merging components of migrated calls, so that the same call features are available on these calls as the original calls. Some of these techniques have been incorporated in commercial products, resulting in improved fault-tolerance.