ECN Based Multi-path Mechanism for VoIP Transmission

By the remarkable improvement of physical performance of networks (such as speed, capacity, etc) which consist of Internet and the diffusion of high-end terminals such as smart-phones, voice over IP (VoIP) is becoming one of the major communication technologies. However current packet networks still can not provide a stable transmission quality and it can cause VoIP call quality degradation. Especially, the main factor affecting VoIP quality is congestion across a network. Multi-homing can be a good solution to avoid points of congestion in the network. We therefore propose Real Time & Multi-path Transmission Protocol (RTMTP), a transport layer protocol in which multiple path real-time transport and effective congestion control are available. Our protocol uses the explicit congestion notification (ECN) mechanism to detect network congestion level and to control transmission rate of VoIP traffic at the sender side. To maximize network bandwidth efficiency of multiple paths, the RTMTP shifts traffic among those paths. Our simulation results show that RTMTP improves VoIP data transmission throughput by effectively utilizing multi-path without voice call quality degradation, and helps users to use more inexpensive access network as much as possible while maintaining an acceptable voice quality.