Performance-Engineered Network Overlays for High Quality Interaction in Virtual Worlds

Overlay hosting systems such as PlanetLab, and cloud computing environments such as Amazon’s EC2, provide shared infrastructures within which new applications can be developed and deployed on a global scale. This paper ex-plores how systems of this sort can be used to enable ad-vanced network services and sophisticated applications that use those services to enhance performance and provide a high quality user experience. Specifically, we investigate how advanced overlay hosting environments can be used to provide network services that enable scalable virtual world applications and other large-scale distributed applications requiring consistent, real-time performance. We propose a novel network architecture called Forest built around per-session tree-structured communication channels that we call comtrees. Comtrees are provisioned and support both unicast and multicast packet delivery. The multicast mechanism is designed to be highly scalable and light-weight enough to support the rapid changes to multicast subscriptions needed for efficient support of state updates within virtual worlds. We evaluate performance using a combination of analysis and experimental measurement of a partial system prototype that supports fully functional distributed game sessions. Our results provide the data needed to enable accurate projections of performance for a variety of session and system configurations

Stateful Anycast for DDoS Mitigation

MEng thesisDistributed denial-of-service (DDoS) attacks can easily cripple victim hosts or networks, yet effective defenses remain elusive. Normal anycast can be used to force the diffusion of attack traffic over a group of several hosts to increase the difficulty of saturating resources at or near any one of the hosts. However, because a packet sent to the anycast group may be delivered to any member, anycast does not support protocols that require a group member to maintain state (such as TCP). This makes anycast impractical for most applications of interest.This document describes the design of Stateful Anycast, a conceptual anycast-like network service based on IP anycast. Stateful Anycast is designed to support stateful sessions without losing anycasts ability to defend against DDoS attacks. Stateful Anycast employs a set of anycasted proxies to direct packets to the proper stateholder. These proxies provide DDoS protection by dropping a sessions packets upon group member request. Stateful Anycast is incrementally deployable and can scale to support many groups

Application of overlay techniques to network monitoring

Measurement and monitoring are important for correct and efficient operation of a network, since these activities provide reliable information and accurate analysis for characterizing and troubleshooting a network’s performance. The focus of network measurement is to measure the volume and types of traffic on a particular network and to record the raw measurement results. The focus of network monitoring is to initiate measurement tasks, collect raw measurement results, and report aggregated outcomes. Network systems are continuously evolving: besides incremental change to accommodate new devices, more drastic changes occur to accommodate new applications, such as overlay-based content delivery networks. As a consequence, a network can experience significant increases in size and significant levels of long-range, coordinated, distributed activity; furthermore, heterogeneous network technologies, services and applications coexist and interact. Reliance upon traditional, point-to-point, ad hoc measurements to manage such networks is becoming increasingly tenuous. In particular, correlated, simultaneous 1-way measurements are needed, as is the ability to access measurement information stored throughout the network of interest. To address these new challenges, this dissertation proposes OverMon, a new paradigm for edge-to-edge network monitoring systems through the application of overlay techniques. Of particular interest, the problem of significant network overheads caused by normal overlay network techniques has been addressed by constructing overlay networks with topology awareness - the network topology information is derived from interior gateway protocol (IGP) traffic, i.e. OSPF traffic, thus eliminating all overlay maintenance network overhead. Through a prototype that uses overlays to initiate measurement tasks and to retrieve measurement results, systematic evaluation has been conducted to demonstrate the feasibility and functionality of OverMon. The measurement results show that OverMon achieves good performance in scalability, flexibility and extensibility, which are important in addressing the new challenges arising from network system evolution. This work, therefore, contributes an innovative approach of applying overly techniques to solve realistic network monitoring problems, and provides valuable first hand experience in building and evaluating such a distributed system

Ontwerp en evaluatie van content distributie netwerken voor multimediale streaming diensten.

Traditionele Internetgebaseerde diensten voor het verspreiden van bestanden, zoals Web browsen en het versturen van e-mails, worden aangeboden via één centrale server. Meer recente netwerkdiensten zoals interactieve digitale televisie of video-op-aanvraag vereisen echter hoge kwaliteitsgaranties (QoS), zoals een lage en constante netwerkvertraging, en verbruiken een aanzienlijke hoeveelheid bandbreedte op het netwerk. Architecturen met één centrale server kunnen deze garanties moeilijk bieden en voldoen daarom niet meer aan de hoge eisen van de volgende generatie multimediatoepassingen. In dit onderzoek worden daarom nieuwe netwerkarchitecturen bestudeerd, die een dergelijke dienstkwaliteit kunnen ondersteunen. Zowel peer-to-peer mechanismes, zoals bij het uitwisselen van muziekbestanden tussen eindgebruikers, als servergebaseerde oplossingen, zoals gedistribueerde caches en content distributie netwerken (CDN's), komen aan bod. Afhankelijk van de bestudeerde dienst en de gebruikte netwerktechnologieën en -architectuur, worden gecentraliseerde algoritmen voor netwerkontwerp voorgesteld. Deze algoritmen optimaliseren de plaatsing van de servers of netwerkcaches en bepalen de nodige capaciteit van de servers en netwerklinks. De dynamische plaatsing van de aangeboden bestanden in de verschillende netwerkelementen wordt aangepast aan de heersende staat van het netwerk en aan de variërende aanvraagpatronen van de eindgebruikers. Serverselectie, herroutering van aanvragen en het verspreiden van de belasting over het hele netwerk komen hierbij ook aan bod

Measurement-based Optimal Routing Strategies on Overlay Architectures

In this thesis, we seek optimal, yet practical, multipath routing algorithms that can minimize the network congestion by exploiting the locally collected measurement data. We first develop a distributed measurement-based routing algorithm to load balance intradomain traffic along multiple paths for multiple unicast sources. Multiple paths are established using overlay nodes. The algorithm is derived from simultaneous perturbation stochastic approximation (SPSA) and does not assume that the gradient of an analytical cost function is known. Instead, it relies on (potentially) noisy estimates from local measurements. We formulate the traffic mapping problem in an optimization framework and show through an analytical model that the algorithm converges to the optimal solution almost surely under a decreasing step size policy. Motivated by practical concerns, we next consider the constant step size case, for which we establish weak convergence. In the second part of this thesis, we consider the problem of load balancing of multicast traffic sessions and generalize our unicast routing algorithm to route both types of traffic simultaneously. We consider three network models that reflect different sets of assumptions regarding multicast capabilities of the network. In addition, we investigate the benefits acquired from implementing additional multicast capabilities by studying the relative performance of the generalized algorithm under the three network models. Throughout this thesis, we rely on an overlay architecture to establish multiple paths between a source and its destination(s) in an IP network. As the performance of the routing algorithms depends on the quality of paths provided by the overlay nodes, it is of interest to carefully locate a limited number of overlay nodes in the network. The final part of this thesis makes use of the discrete stochastic optimization methods and presents an optimal solution based on Stochastic Comparison (SC) algorithm to locate overlay nodes given a set of sources and their corresponding destination(s). Motivated by the impracticality of stochastic comparison algorithm in an online setting due to its computational complexity, we provide a computationally efficient heuristic solution. We show through a detailed simulation study that the performance obtained by the heuristic solution is comparable to that of optimal algorithm

Simple and stable dynamic traffic engineering for provider scale ethernet

Trabalho apresentado no âmbito do Mestrado em Engenharia Informática, como requisito parcial para obtenção do grau de Mestre em Engenharia InformáticaThe high speeds and decreasing costs of Ethernet solutions has motivated providers’ interest in using Ethernet as the link layer technology in their backbone and aggregation networks. Provider scale Ethernet offers further advantages, providing not only an easy to manage solution for multicast traffic, but also transparent interconnection between clients’ LANs. These Ethernet deployments face altogether different design issues, requiring support for a significantly higher number of hosts. This support relies on hierarquization, separating address and virtual network spaces of customers and providers. In addition, large scale Ethernet solutions need to grant forwarding optimality. This can be achieved using traffic engineering approaches. Traffic engineering defines the set of engineering methods and techniques used to optimize the flow of network traffic. Static traffic engineering approaches enjoy widespread use in provider networks, but their performance is greatly penalized by sudden load variations. On the other hand, dynamic traffic engineering is tailored to adapt to load changes. However, providers are skeptical to adopt dynamic approaches as these induce problems such as routing instability, and as a result, network performance decreases. This dissertation presents a Simple and Stable Dynamic Traffic Engineering framework (SSD-TE), which addresses these concerns in a provider scale Ethernet scenario. The validation results show that SSD-TE achieves better or equal performance to static traffic engineering approaches, whilst remaining both stable and responsive to load variations

Optimization-based rate control in overlay multicast.

Zhang Lin.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 74-78).Abstracts in English and Chinese.Chapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Why use economic models? --- p.1Chapter 1.2 --- Why Overlay? --- p.2Chapter 1.3 --- Our Contribution --- p.3Chapter 1.4 --- Thesis Organization --- p.5Chapter Chapter 2 --- Related Works --- p.7Chapter 2.1 --- Overlay Multicast --- p.7Chapter 2.2 --- IP Multicast Congestion Control --- p.11Chapter 2.2.1 --- Architecture Elements of IP Multicast Congestion Control --- p.11Chapter 2.2.2 --- Evaluation of Multicast Video --- p.13Chapter 2.2.3 --- End-to-End Schemes --- p.14Chapter 2.2.4 --- Router-supported Schemes --- p.16Chapter 2.2.5 --- Conclusion --- p.19Chapter 2.3 --- Optimization-based Rate Control in IP unicast and multicast --- p.20Chapter 2.3.1 --- Optimization-based Rate Control for Unicast Sessions --- p.21Chapter 2.3.2 --- Optimization-based Rate Control for Multi-rate Multicast Sessions --- p.24Chapter Chapter 3 --- Overlay Multicast Rate Control Algorithms --- p.27Chapter 3.1 --- Motivations --- p.27Chapter 3.2 --- Problem Statement --- p.28Chapter 3.2.1 --- Network Model --- p.28Chapter 3.2.2 --- Problem Formulation --- p.29Chapter 3.2.3 --- Algorithm Requirement --- p.33Chapter 3.3 --- Primal-based Algorithm --- p.34Chapter 3.3.1 --- Notations --- p.34Chapter 3.3.2 --- An Iterative Algorithm --- p.36Chapter 3.3.3 --- Convergence Analysis --- p.37Chapter 3.3.3.1 --- Assumptions --- p.37Chapter 3.3.3.2 --- Convergence with various step-sizes --- p.39Chapter 3.3.3.3 --- Theorem Explanations --- p.39Chapter 3.4 --- Dual-based Algorithm --- p.40Chapter 3.4.1 --- The Dual Problem --- p.41Chapter 3.4.2 --- Subgradient Algorithm --- p.43Chapter 3.4.3 --- Interpretation of the Prices --- p.44Chapter 3.4.4 --- Convergence Analysis --- p.45Chapter Chapter 4 --- Protocol Description and Performance Evaluation --- p.47Chapter 4.1 --- Motivations --- p.47Chapter 4.2 --- Protocols --- p.47Chapter 4.2.1 --- Notations --- p.48Chapter 4.2.2 --- Protocol for primal-based algorithm --- p.48Chapter 4.2.3 --- Protocol for dual-based algorithm --- p.53Chapter 4.3 --- Performance Evaluation --- p.57Chapter 4.3.1 --- Simulation Setup --- p.57Chapter 4.3.2 --- Rate Convergence Properties --- p.59Chapter 4.3.3 --- Data Rate Constraint --- p.67Chapter 4.3.4 --- Link Measurement Overhead --- p.68Chapter 4.3.5 --- Communication Overhead --- p.70Chapter Chapter 5 --- Conclusion Remarks and Future Work --- p.73References --- p.7