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1. Design of a Stochastic Traffic Regulator for End-to-End Network Delay Guarantees

   https://doi.org/10.1109/TNET.2022.3181858  

   Boroujeny, Massieh Kordi ; Mark, Brian L. ( June 2022 , IEEE/ACM Transactions on Networking)

   Providing end-to-end network delay guarantees in packet-switched networks such as the Internet is highly desirable for mission-critical and delay-sensitive data transmission, yet it remains a challenging open problem. Since deterministic bounds are based on the worst-case traffic behavior, various frameworks for stochastic network calculus have been proposed to provide less conservative, probabilistic bounds on network delay, at least in theory. However, little attention has been devoted to the problem of regulating traffic according to stochastic burstiness bounds, which is necessary in order to guarantee the delay bounds in practice. We design and analyze a stochastic traffic regulator that can be used in conjunction with results from stochastic network calculus to provide probabilistic guarantees on end-to-end network delay. Two alternative implementations of the stochastic regulator are developed and compared. Numerical results are provided to demonstrate the performance of the proposed stochastic traffic regulator. 

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2. Phase-type bounds on network performance

   https://doi.org/10.1109/CISS.2018.8362284  

   Boroujeny, Massieh Kordi ; Ephraim, Yariv ; Mark, Brian L. ( March 2018 , 52nd Annual Conference on Information Sciences and Systems (CISS))

   Evaluation of end-to-end network performance using realistic traffic models is a challenging problem in networking. The classical theory of queueing networks is feasible only under rather restrictive assumptions on the input traffic models and network elements. An alternative approach, first proposed in the late 1980s, is to impose deterministic bounds on the input traffic that can be used as a basis for a network calculus to compute end-to-end network delay bounds. Such deterministic bounds are inherently loose as they must accommodate worst case scenarios. Since the early 1990s, efforts have shifted to development of a stochastic network calculus to provide probabilistic end-to-end performance bounds. In this paper, we capitalize on the approach of stochastically bounded burstiness (SBB) which was developed for a general class of bounding functions, and was demonstrated for a bound that is based on a mixture distribution. We specialize the SBB bounds to bounds based on the class of phase-type distributions, which includes mixture distributions as a particular case. We develop the phase-type bounds and demonstrate their performance. 

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3. Fitting Network Traffic to Phase-Type Bounds

   https://doi.org/10.1109/CISS48834.2020.1570617448  

   Boroujeny, Massieh Kordi ; Mark, Brian L. ; Ephraim, Yariv ( March 2020 , 2020 54th Annual Conference on Information Sciences and Systems (CISS)

   Network traffic is difficult to characterize due to its random, bursty nature. Even if a traffic source could be fit to a stochastic model with reasonable accuracy, analysis of end-to-end network performance metrics for such traffic models is generally intractable. In prior work, an approach to characterize traffic burstiness using a bound based on the class of phase-type distributions was proposed. Such phase-type bounds could be applied in conjunction with stochastic network calculus to derive probabilistic end-to-end delay bounds for a traffic stream. In this paper, we focus on the problem of estimating a tight phase-type burstiness bound for a given traffic trace. We investigate a method based on least squares and another based on the expectation-maximization algorithm. Our numerical results compare the two approaches in the scenario of a heavy-tailed M/G/1 queue. We find that while both methods are viable approaches for deriving phase-type bounds on traffic burstiness, the least squares approach performs better, particularly when a tail limit is imposed. 

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4. M. Kordi Boroujeny and B.L. Mark, "A Framework for Providing Stochastic Delay Guarantees in Communication Networks," IEEE ICC 2021 Workshop on Time-sensitive and Deterministic Networking, Montreal, Canada, June 2021

   Kordi Boroujeny, Massieh ; Mark, Brian L. ( June 2021 , IEEE ICC 2021 Workshop on Time-sensitive and Deterministic Networking)

   null (Ed.)

   The provisioning of delay guarantees in packet-switched networks such as the Internet remains an important, yet challenging open problem. We propose and evaluate a framework, based on results from stochastic network calculus, for guaranteeing stochastic bounds on network delay at a statistical multiplexer. The framework consists of phase-type traffic bounds and moment generating function traffic envelopes, stochastic traffic regulators to enforce the traffic bounds, and an admission control scheme to ensure that a stochastic delay bound is maintained for a given set of flows. Through numerical examples, we show that a stochastic delay bound is maintained at the multiplexer, and contrast the proposed framework to an approach based on deterministic network calculus. 

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5. Bounding Network-Induced Delays of Wireless PRP Infrastructure for Industrial Control Systems

   https://doi.org/10.1109/ICC.2019.8761893  

   Yang, Huan ; Cheng, Liang ( May 2019 , ICC 2019 - 2019 IEEE International Conference on Communications (ICC))

   Recently, wireless communication technologies, such as Wireless Local Area Networks (WLANs), have gained increasing popularity in industrial control systems (ICSs) due to their low cost and ease of deployment, but communication delays associated with these technologies make it unsuitable for critical real-time and safety applications. To address concerns on network-induced delays of wireless communication technologies and bring their advantages into modern ICSs, wireless network infrastructure based on the Parallel Redundancy Protocol (PRP) has been proposed. Although application-specific simulations and measurements have been conducted to show that wireless network infrastructure based on PRP can be a viable solution for critical applications with stringent delay performance constraints, little has been done to devise an analytical framework facilitating the adoption of wireless PRP infrastructure in miscellaneous ICSs. Leveraging the deterministic network calculus (DNC) theory, we propose to analytically derive worst-case bounds on network- induced delays for critical ICS applications. We show that the problem of worst-case delay bounding for a wireless PRP network can be solved by performing network-calculus-based analysis on its non-feedforward traffic pattern. Closed-form expressions of worst-case delays are derived, which has not been found previously and allows ICS architects/designers to compute worst- case delay bounds for ICS tasks in their respective application domains of interest. Our analytical results not only provide insights into the impacts of network-induced delays on latency- critical tasks but also allow ICS architects/operators to assess whether proper wireless RPR network infrastructure can be adopted into their systems. 

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