VORAL: a system for Voice over IP Routing in Application Layer

Abstract

There are three key metrics (end-to-end delay, packet loss rate and delay variation) for determining the quality of Voice over IP (VoIP). The impact of delay variation can be reduced by de-jitter buffering at a receiver side. The impairment caused by the packet delay and loss can be reduced by routing the traffic through an Internet path with a better quality. However, the current Internet infrastructure has not yet supported a complete QoS routing. Consequently, the quality of VoIP today, especially over a wide area network for international calls, is often unbearable. We present a system VORAL (Voice Over IP Routing in Application Layer) that can significantly improve the QoS of VoIP by routing the voice packets in the application layer through various relay servers in the Internet. The routing techniques use R-factor, a parameter determined by packet loss rate and packet delay, to select a path with the best VoIP quality for a call. The paths of incoming traffic and the outgoing traffic can be different and be dynamically changed during a call. The usefulness of the VORAL system is further validated by an experimental VoIP service between US and Taiwan.