Unified Comms

1-800-OVERLAYS: Using Overlay Networks to Improve VoIP Quality

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Executive Summary

Every service provider is opting for Voice over Internet protocol (VoIP) due to its many novel features and capability to reduce costs. This transition is also happening because VoIP is easily able to match the quality and reliability offered by the existing PSTN. To support high quality interactive conversations through low latency and jitter, VoIP applications make use of UDP to transfer data. This results in performance degradations caused by packet loss and network failures as even the best effort service model of Internet does not provide inherent quality of service guarantees. This paper presents two algorithms to improve the performance of such VoIP applications. Using these mechanisms, one can recover localized packet loss and rapidly reroute in the event of network failures. As these algorithms are deployed on the routers of an application-level overlay network, no changes to the underlying infrastructure are required. The results obtained through initial experiments show that both the approaches presented in the paper can be composed to yield voice quality on par with the PSTN. The paper describes how the current conditions are making the deployment of PSTN quality VoIP slow. To tackle this problem, the paper suggests the use of an overlay network to segment end-to-end paths into shorter overlay hops with the aim to recover lost packets using limited hop-by-hop retransmissions. This is done to overcome the bursty loss pattern of the Internet.

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