Faculty Publications
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Item CARED: Cautious Adaptive RED gateways for TCP/IP networks(2012) Tahiliani, M.P.; Shet, K.C.; Basavaraju, T.G.Random Early Detection (RED) is a widely deployed active queue management algorithm that improves the overall performance of the network in terms of throughput and delay. The effectiveness of RED algorithm, however, highly depends on appropriate setting of its parameters. Moreover, the performance of RED is quite sensitive to abrupt changes in the traffic load. In this paper, we propose a Cautious Adaptive Random Early Detection (CARED) algorithm that dynamically varies maximum drop probability based on the level of traffic load to improve the overall performance of the network. Based on extensive simulations conducted using Network Simulator-2 (ns-2), we show that CARED algorithm reduces the packet drop rate and achieves high throughput as compared to RED, Adaptive RED and Refined Adaptive RED. Unlike other RED based algorithms, CARED algorithm does not introduce new parameters to achieve performance gain and hence can be deployed without any additional complexity. © 2011 Elsevier Ltd. All rights reserved.Item Implementation and validation of BLUE and PI queue disciplines in ns-3(Elsevier B.V., 2018) Jain, V.; Mittal, V.; K S, S.; Tahiliani, M.P.High queuing delay arising out of the bufferbloat problem has reignited research in the area of Active Queue Management (AQM). The Internet Engineering Task Force (IETF) has created a new working group to discuss the deployment feasibility of existing and upcoming AQM algorithms (or queuing disciplines) in the Internet. Network simulations are essential to gain an accurate and deep understanding of the network algorithms before they are deployed in the Internet. ns-3 is among the most widely used network simulators, and the recent addition of Linux-like traffic control subsystem in ns-3 makes it highly suitable and reliable for studying the performance of queuing disciplines. However, the current traffic control subsystem in ns-3 has very few queuing disciplines. In an effort to provide support for more queuing disciplines and foster active research in this area, we implement two popular algorithms in ns-3: BLUE and Proportional Integral controller (PI). This paper discusses the implementation and validation of the proposed models in ns-3, and presents a detailed comparative study of both queuing disciplines based on the evaluation guidelines provided in RFC 7928. © 2018 Elsevier B.V.Item Towards a better understanding and analysis of controlled delay (CoDel) algorithm by using fluid modelling(Institution of Engineering and Technology journals@theiet.org, 2019) Patil, S.D.; Tahiliani, M.P.In this study, a modified fluid model is proposed to understand the design of controlled delay (CoDel) algorithm for active queue management (AQM) and analyse its sensitivity to parameter settings. CoDel significantly differs from other AQM algorithms because it operates at the head of the queue and adopts a deterministic packet drop strategy, unlike other algorithms that operate at the tail and adopt a probabilistic packet drop strategy. The correctness of the proposed fluid model is verified by comparing its results with those obtained from ns-2. Subsequently, using the model developed in this study, the authors analyse the performance of CoDel algorithm by changing its internal parameters and modifying its control law. They highlight the role of the internal parameters and control law on the ability of the CoDel algorithm to control queue delay. Their analysis shows that the CoDel algorithm is sensitive to its parameter settings and that its control law requires minor modifications to gain a better control over the queue delay. © The Institution of Engineering and Technology 2018.Item Minstrel PIE: Curtailing queue delay in unresponsive traffic environments(Elsevier B.V., 2019) Patil, S.D.; Tahiliani, M.P.Active Queue Management (AQM) algorithms aim to maintain a proper trade-off between queue delay and bottleneck link utilization. However, it is often noticed that this trade-off is not achieved convincingly when unresponsive UDP flows coexist with responsive TCP flows. This paper proposes an extension to Proportional Integral controller Enhanced (PIE) algorithm called Minstrel PIE, which adapts the reference queue delay to improve the trade-off between queue delay and link utilization when unresponsive flows share the same bottleneck queue as responsive flows. Extensive evaluations through simulations and real time experiments demonstrate that Minstrel PIE improves the performance of PIE in the presence of unresponsive flows, and delivers similar performance otherwise. Moreover, the Minstrel PIE algorithm does not introduce new knobs to improve the performance of PIE and hence, can be easily deployed without any additional complexity. © 2019 Elsevier B.V.Item Revisiting design choices in queue disciplines: The PIE case(Elsevier B.V., 2020) Imputato, P.; Avallone, S.; Tahiliani, M.P.; Ramakrishnan, G.Bloated buffers in the Internet add significant queuing delays and have a direct impact on the user perceived latency. There has been an active interest in addressing the problem of rising queue delays by designing easy-to-deploy and efficient Active Queue Management (AQM) algorithms for bottleneck devices. The real deployment of AQM algorithms is a complex task because the efficiency of every algorithm depends on appropriate setting of its parameters. Hence, the design of AQM algorithms is usually entrusted on simulation environments where it is relatively straightforward to evaluate the algorithms with different parameter configurations. Unfortunately, several factors that affect the efficiency of AQM algorithms in real deployment do not manifest during simulations, and therefore, lead to inefficient design of the AQM algorithm. In this paper, we revisit the design considerations of Proportional Integral controller Enhanced (PIE), an algorithm widely considered for network deployment, and extensively evaluate its performance using a Linux based testbed. Our experimental study reveals some performance anomalies in certain circumstances and we prove that they can be attributed to a specific design choice of PIE, namely the use of the estimated departure rate to compute the expected queuing delay. Therefore, we designed an alternative approach based on packet timestamps, implemented it in the Linux kernel and proved its effectiveness through an experimental campaign. © 2020