A Flow-Level Performance Evaluation of Elastic Traffic Under Low Latency Queuing System

Internet tends progressively to be more interactive by supporting real-time communications into this packet-based environment. It is anticipated that online applications will rapidly develop and contribute by a significant amount of traffic in the near future. These applications have strict requirements in terms of delay and throughput which can't be met only if they are prior. However, at high demand of real-time traffic, elastic traffic (which is transported generally by TCP) may not have sufficient resources to be transported with reasonable quality of service (QoS). Therefore, it is primordial to manage properly the resource-network in order to provide the QoS required by both each type of services. In this paper, we present a new fluid model to evaluate the performance of elastic traffic under Low Latency Queuing (LLQ) system combining a priority queue for delay-sensitive applications with a number of Class Based Weighed Fair Queues (CBWFQ) for elastic traffic. The originality of our contribution consists on focusing on the average total number of flows passing through the whole system by approximating it as a lossless best effort system with total load equal to the total carried load of the original system (no blocked load). The core of our analysis is based on some approximations proven for balanced fairness allocation, which provides a reasonable framework for estimating bandwidth sharing among elastic traffic for best effort allocations. Results issued from this allocation are then exploited to deduce the performance of CBWFQ system. Detailed packet level simulations are used to verify the effectiveness and the accuracy of our analysis. The approach presented in this paper allows a rapid performance evaluation of elastic or rate-adaptive traffic circulating in the actual networks.