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Running time sensitive multimedia services such as voice-over-IP (VoIP) and video-on-demand (VoD) on all-ip networks may have lower quality, i.e. Quality of Service (QoS), than its counterpart on conventional circuit-switched networks. We could enhance overall QoS without investing more resources if routers could forward packets based on their timeliness and QoS class giving important late packets proper precedence. This paper proposes a charge-based optimization model for packet scheduling aiming to maximize overall QoS satisfaction factor. We also developed a simple and effective scheduling policy based on this concept for the environments where each packet has a predefined hop-by-hop traveling schedule. Routers are assumed in three different queue architectures: ideal single preemptive queue and practical multiple FIFO queue with and without a priority queue. To forward a packet, a router first assigns an adequate profit function to the packet based on its timeliness and QoS class as well as the loading status of the succeeding routers along its traveling path, and then inserts the packet into an appropriate position in the output queues. The performance of this approach is evaluated by simulation using NS-2 network simulator. Simulation results show that, under heavy load, our approach can outperform easily the simulated priority queue that differentiates QoS class only.
Date of Conference: 19-21 Aug. 2009