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Habilitation à diriger des recherches

Contributions to the Performance Modeling of Computer Networks

Thomas Begin 1
1 DANTE - Dynamic Networks : Temporal and Structural Capture Approach
Inria Grenoble - Rhône-Alpes, LIP - Laboratoire de l'Informatique du Parallélisme, IXXI - Institut Rhône-Alpin des systèmes complexes
Abstract : Computer networks have become part of our daily life and, to some extent, a key element of our modern society. Over the last two decades the number of Internet users have surged from 147 million to over 4 billion and many applications have emerged (e.g., instant messaging, voice over IP, social networking, video on demand). To meet these new demands, computer networks have undergone tremendous changes, augmenting their performance, their services and providing access through wireless communications. A case in point is the fast development of the IEEE 802.11 standard (commercially known as WiFi) that experienced many changes since its release in 1997. More recently, NFV (Network Function Virtualization) emerged as a promising paradigm to bring flexibility and efficiency to the networks by replacing specialized and proprietary hardware with software ran over commodity hardware. Because of the constant renewal of networking technologies and increasing needs for Quality of Service (QoS), the performance modeling of computer networks remains a challenging and crucial issue. This habilitation thesis describes a selection of my scientific contributions in the scope of computer networks and performance evaluation. Chapter 1 comprises a description of my research activities and a discussion on some potential forthcoming challenges. Chapter 2 is devoted to my contributions in the context of NFV. More precisely, it presents an analytical queueing model to evaluate the performance of a network function (implemented as a software) commuting packets, aka a virtual switch (vSwitch). The model delivers performance metrics such as the buffer occupancy, the loss rate and the sojourn time of packets in the vSwitch. The proposed solution is conceptually simple, computationally efficient and generally accurate. An example based on a real-life case study illustrates how the model can help in determining an adequate setting of the vSwitch parameters. Chapter 3 deals with the issue of modeling IEEE-802.11 based Wireless Local Area Networks (WLANs). It describes a performance modeling method that estimates the attained throughput of each Access Point (AP), as a function of the WLAN’s conflict graph, the AP loads, the frame sizes, and the link transmission rates. The modeling approach employs a Divide-and-Conquer strategy that breaks down the original problem into multiple sub-problems, whose solutions are then combined to provide the solution to the original problem. The model accuracy is generally good and its application may help to assign AP channels when configuring a WLAN. Chapter 4 considers Ph/Ph/c and Ph/Ph/c/N queues that can be viewed as a common model of multi-server facilities. It introduces a simple approximate solution for the equilibrium probabilities in such queues based on a reduced state description in order to circumvent the well-known combinatorial growth of the number of states inherent in the classical state description. The number of equations to solve in our approach increases linearly with the number of servers and phases in the service time distribution. The overall accuracy of the proposed approximation appears very good, and tends to become excellent as the number of servers increases. This thesis ends with Chapter 5 that provides work methods and good practices derived from my experience, as well as a number of prospects for the future.
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Submitted on : Tuesday, December 11, 2018 - 12:22:41 PM
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Thomas Begin. Contributions to the Performance Modeling of Computer Networks. Networking and Internet Architecture [cs.NI]. Université Claude Bernard Lyon 1, 2018. ⟨tel-01951250⟩

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