Using differentiated services to support Internet telephony

Abstract

Internet telephony has been deemed as a promising candidate for the next generation telephone system. However, unstable voice quality is the main problem that prevents the Internet Telephone from competing with the traditional circuit switched telephone. Current Internet supports only a best-effort service class, which does not provide any bandwidth or delay guarantee for the voice packets. During congestion, consecutive packets get lost or miss the deadlines, which results in severe degradation in voice quality. In this paper, we introduce the concept of using differentiated service model to solve the problem. First, we propose a class-based model to separate the voice streams from the best-effort traffic. Then we use a selective dropping model to further prevent consecutive packet losses to satisfy the ( m, k) firm guarantee [9] requirement, and thereby enhance the voice quality in the Internet telephony services. The model is implemented using the ns simulator [18]. The performance of the proposed technique is evaluated through the simulator and the results justify the validity of using the model for Internet telephony.