Faculty Publications
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Item Implementation and evaluation of Proportional Integral Controller Enhanced (PIE) algorithm in ns-3(Association for Computing Machinery acmhelp@acm.org, 2016) Shravya, K.S.; Murali, S.; Tahiliani, M.P.This paper proposes a new ns-3 model and presents the evaluation results for Proportional Integral controller Enhanced (PIE), a recently designed Active Queue Management (AQM) mechanism to address the problem of bufferbloat. The problem of bufferbloat arises due to the presence of large unmanaged buffers in routers. This leads to high queuing latency and significantly degrades the performance of time-sensitive and interactive traffic. AQM mechanisms that aim to address the problem of bufferbloat try to achieve an optimal trade-off between high link utilization and low mean queue length. PIE is a lightweight AQM mechanism that tries to achieve the same. To our knowledge, ns-3 network simulator does not have a model for simulating PIE. Hence, in this paper, we implement a ns-3 model for PIE, and show that the results obtained from it are in line with those obtained from the ns-2 model of PIE, implemented by its authors. © 2016 ACM.Item Design and implementation of AQM evaluation suite for ns-3(Association for Computing Machinery acmhelp@acm.org, 2017) Deepak, A.; Shravya, K.S.; Tahiliani, M.P.Excessive buffering in network devices should be avoided because it leads to a series of performance issues such as high queuing latency and variations in delay. Active Queue Management (AQM) algorithms play a vital role in monitoring and controlling the queue length in these devices. Recently there has been a significant progress in the design and development of new AQM algorithms. However, thoroughly evaluating the performance of AQM algorithms is a nontrivial task. In an effort to simplify this, the Active Queue Management and Packet Scheduling Working Group at IETF have proposed informational guidelines in RFC 7928 to test the applicability, performance and deployment complexity of AQM algorithms. This paper presents the design and implementation of an AQM evaluation framework for ns-3 which helps to quickly study the performance of AQM algorithms based on the guidelines mentioned in RFC 7928. The proposed framework automates simulation setup, topology creation, trafiéc generation, program execution, results collection and their graphical representation using ns-3, based on the scenarios mentioned in the RFC. © 2017 ACM.Item Implementation and validation of random exponential marking (REM) in ns-3(Institute of Electrical and Electronics Engineers Inc., 2018) Tarte, I.; Joshi, A.R.; Navya, R.S.; Tahiliani, M.P.The problem of bufferbloat has reignited interest in studying Active Queue Management (AQM) algorithms. Significant efforts have been taken by AQM and Packet Scheduling Working Group at IETF to bring more awareness about the performance benefits of deploying AQM algorithms in the Internet. However, experimental analysis of these algorithms is necessary prior to real time deployment. Network simulators like ns-3 are useful tools to perform such preliminary studies. Random Exponential Marking (REM) is one of the popular AQM algorithms. It decouples congestion measure from performance measure, and aims to stabilize the performance measure around the target queue length regardless of the number of users. This paper presents the implementation of a new model for REM in ns-3. The correctness of the proposed model has been validated by comparing the results obtained from it, to those obtained from the ns-2 model developed by authors of REM. © 2017 IEEE.Item BBRvl vs BBRv2: Examining Performance Differences through Experimental Evaluation(IEEE Computer Society help@computer.org, 2020) Nandagiri, A.; Tahiliani, M.P.; Misra, V.; Ramakrishnan, K.K.BBR, a congestion control algorithm proposed by Google, regulates the source sending rate by deriving an estimate of the bottleneck's available bandwidth and RTTof the path. The initial version of BBR, called BBRvl, was found to be unfair, getting higher than the fair share of bandwidth when co-existing on bottleneck links with other congestion control algorithms. It also does not perform as well with networks having routers with shallow buffers. To overcome these concerns, a newer version, called BBRv2, has been proposed. Our goal in this paper is to understand the differences between the two versions and examine the primary reasons behind the improvement in performance of BBRv2. We present an experimental evaluation of BBRvl and BBRv2, evaluating their fairness across connections using the same protocol (intra-protocol fairness) and using different protocols (inter-protocol fairness) as well as delay and link utilization. From experiments with shallow and deep buffers, BBRv2 is most effective when it uses Explicit Congestion Notification (ECN), but fairness issues continue to exist in BBRv2 when ECN is disabled. A concern for BBRv2 is that it is somewhat complex to deploy in Wide Area Networks (WAN) because of the dependency with the DCTCP-style reduction of the congestion window, which is primarily usable in low-feedback delay Data Center Networks. © 2020 IEEE.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 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