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Democratizing Content Distribution
, 2007
"... "Behold how good and how pleasant it is for brethren to dwell together in unity." Psalms 1331 To my future wife Jennifer for her warmth and support and To my brother Daniel for his courage of convictions v ..."
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"Behold how good and how pleasant it is for brethren to dwell together in unity." Psalms 1331 To my future wife Jennifer for her warmth and support and To my brother Daniel for his courage of convictions v
Very LargeScale Neighborhood Search Algorithms for the Design of Service Overlay Networks
"... Service Overlay Networks (SONs) allow virtual operators to create and deploy valueadded Internet services with Quality of Service guarantees, while leaving the underlying network infrastructure unchanged. The deployment of a SON can be very expensive, and hence its planning requires careful decisio ..."
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Service Overlay Networks (SONs) allow virtual operators to create and deploy valueadded Internet services with Quality of Service guarantees, while leaving the underlying network infrastructure unchanged. The deployment of a SON can be very expensive, and hence its planning requires careful decisions, including the overlay nodes ’ placement and the capacity provisioning of the access links that connect the endusers to the SON infrastructure. In this work we first propose a novel Integer Linear Programming (ILP) model for the overlay network design problem which selects the optimal number and position of overlay nodes, the capacity reserved on each overlay link, as well as the optimal routing of the incoming traffic demands. Since such model can be solved to the optimum only for small network instances, we further propose an efficient and novel tabu search based heuristic for the planning of SONs that combines polynomial size and very largescale neighborhoods. The very largescale neighborhood of the solution given by tabu search is explored efficiently to obtain in a short time a new one that is both far from the current solution and costdecreasing. We provide numerical results of the proposed heuristic on a set of realistic, largesize instances, including real ISP topologies, and discuss the effect of different parameters on the characteristics of the planned networks. Furthermore, we compare such results with the bound obtained solving our ILP model in small network scenarios. We show that in the considered network topologies the proposed heuristic performs very close to the optimum with a short computation time, thus providing a promising framework for the design of SONs.
OVERVIEW AND CHALLENGES OF OVERLAY NETWORKS: A SURVEY
"... Nowadays, a very useful platform is becoming widely used to deploy new services and applications in the Internet: the overlay networks. These networks create a virtual topology on top of existing ones with the purpose of providing several different services such as file sharing or content delivery. ..."
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Nowadays, a very useful platform is becoming widely used to deploy new services and applications in the Internet: the overlay networks. These networks create a virtual topology on top of existing ones with the purpose of providing several different services such as file sharing or content delivery. This survey focuses on diverse research issues concerning overlay networks applicability and management strategies required for emergent network environments. In this way, mobility, security, scalability, dependability and resource constraints are studied with regard to overlay networks. We finally discuss the evolution of these networks in order to satisfy new technological improvements.
The KObserver Problem in Computer Networks
"... For any nonnegative integer K, a Kobserver P of a network N is a set of nodes in N such that each message, that travels at least K hops in N, is handled (and so observed) by at least one node in P. A Kobserver P of a network N is minimum iff the number of nodes in P is less than or equal the numb ..."
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For any nonnegative integer K, a Kobserver P of a network N is a set of nodes in N such that each message, that travels at least K hops in N, is handled (and so observed) by at least one node in P. A Kobserver P of a network N is minimum iff the number of nodes in P is less than or equal the number of nodes in every Kobserver of N. The nodes in a minimum Kobserver of a network N can be used to monitor the message traffic in network N and collect traffic statistics, detect patterns of denialofservice attacks when they occur in N, and act as firewalls to identify and discard attack messages from N. In this paper, we consider the problem of constructing a minimum Kobserver for any given network. We show that the problem is NPhard for general networks, and give linear time algorithms for constructing minimum or nearminimum Kobservers for special classes of networks: trees, rings, Lrings, and large grids. 1 1
Efficient Design and Performance Analysis of Wireless Mesh and Overlay Networks
, 2010
"... This document summarizes part of the research work I have been developing during the last five years. My research interests focused on two main topics, namely (1) the design and evaluation of wireless networked computer systems (more specifically, of Wireless Mesh and Community networks), and (2) th ..."
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This document summarizes part of the research work I have been developing during the last five years. My research interests focused on two main topics, namely (1) the design and evaluation of wireless networked computer systems (more specifically, of Wireless Mesh and Community networks), and (2) the planning of overlay networks and the distributed overlay formation problem. Wireless Mesh Networks represent an effective means to provide broadband wireless connectivity without the need of a costly wired network infrastructure. The flexibility provided by this wireless network technology has fostered the development of new communication paradigms, like Wireless Mesh Community Networks, where devices owned and managed by different individuals cooperate to extend the network coverage. In this context, we designed efficient and secure communication protocols at the Medium Access Control (MAC) and routing levels. We developed powercontrolled, multichannel MAC protocols for mesh nodes equipped with directional antennas; these protocols increase the spatial reuse and therefore the overall network performance. We then tackled the routing problem in wireless multihop networks using both exact models and heuristics; we further proposed
ClouDiA: A Deployment Advisor for Public Clouds
"... An increasing number of distributed datadriven applications are moving into shared public clouds. By sharing resources and operating at scale, public clouds promise higher utilization and lower costs than private clusters. To achieve high utilization, however, cloud providers inevitably allocate vi ..."
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An increasing number of distributed datadriven applications are moving into shared public clouds. By sharing resources and operating at scale, public clouds promise higher utilization and lower costs than private clusters. To achieve high utilization, however, cloud providers inevitably allocate virtual machine instances noncontiguously, i.e., instances of a given application may end up in physically distant machines in the cloud. This allocation strategy can lead to large differences in average latency between instances. For a large class of applications, this difference can result in significant performance degradation, unless care is taken in how application components are mapped to instances. In this paper, we propose ClouDiA, a general deployment advisor that selects application node deployments minimizing either (i) the largest latency between application nodes, or (ii) the longest critical path among all application nodes. ClouDiA employs mixedinteger programming and constraint programming techniques to efficiently search the space of possible mappings of application nodes to instances. Through experiments with synthetic and real applications in Amazon EC2, we show that our techniques yield a 15 % to 55 % reduction in timetosolution or service response time, without any need for modifying application code. 1.
Best Upgrade Plans for Large Road Networks
"... Abstract. In this paper, we consider a new problem in the context of road network databases, named Resource Constrained Best Upgrade Plan computation (BUP, for short). Consider a transportation network (weighted graph) G where a subset of the edges are upgradable, i.e., for each such edge there is a ..."
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Abstract. In this paper, we consider a new problem in the context of road network databases, named Resource Constrained Best Upgrade Plan computation (BUP, for short). Consider a transportation network (weighted graph) G where a subset of the edges are upgradable, i.e., for each such edge there is a cost, which if spent, the weight of the edge can be reduced to a specific new value. Given a source and a destination in G, and a budget (resource constraint) B, the BUP problem is to identify which upgradable edges should be upgraded so that the shortest path distance between source and destination (in the updated network) is minimized, without exceeding the available budget for the upgrade. In addition to transportation networks, the BUP query arises in other domains too, such as telecommunications. We propose a framework for BUP processing and evaluate it with experiments on large, real road networks. 1
Overlay Networks Formation: Models and Algorithms
, 2009
"... Overlay networks have recently emerged as an effective means to provide a flexible, robust, and scalable platform for distributed applications, while leaving the underlying Internet infrastructure unchanged. This work tackles the overlay network design problem considering both centralized and fully ..."
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Overlay networks have recently emerged as an effective means to provide a flexible, robust, and scalable platform for distributed applications, while leaving the underlying Internet infrastructure unchanged. This work tackles the overlay network design problem considering both centralized and fully distributed approaches. On one hand, we address the centralized overlay network design problem using the Service Overlay Network (SON) paradigm, and we propose several mathematical models and heuristics for the optimal design of SONs. More specifically, we introduce two network optimization models that determine the optimal assignment of users to access overlay nodes, as well as the capacity reserved for each overlay link, while taking accurate account of traffic routing. We also propose two overlay network design models that further select the optimal number and location of the overlay nodes to be deployed, as well as the optimal coverage of network users to maximize the SON operator’s profit. Furthermore, we develop a set of efficient SON design heuristics to get nearoptimal solutions for largescale network instances in a
Models and Algorithms for the Design . . .
, 2008
"... Service Overlay Networks (SONs) can provide endtoend Quality of Service guarantees in the Internet without ..."
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Service Overlay Networks (SONs) can provide endtoend Quality of Service guarantees in the Internet without
Best Upgrade Plans for Large Road Networks
"... Abstract. In this paper, we consider a new problem in the context of road network databases, named Resource Constrained Best Upgrade Plan computation (BUP, for short). Consider a transportation network (weighted graph) G where a subset of the edges are upgradable, i.e., for each such edge there is a ..."
Abstract
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Abstract. In this paper, we consider a new problem in the context of road network databases, named Resource Constrained Best Upgrade Plan computation (BUP, for short). Consider a transportation network (weighted graph) G where a subset of the edges are upgradable, i.e., for each such edge there is a cost, which if spent, the weight of the edge can be reduced to a specific new value. Given a source and a destination in G, and a budget (resource constraint) B, the BUP problem is to identify which upgradable edges should be upgraded so that the shortest path distance between source and destination (in the updated network) is minimized, without exceeding the available budget for the upgrade. In addition to transportation networks, the BUP query arises in other domains too, such as telecommunications. We propose a framework for BUP processing and evaluate it with experiments on large, real road networks. 1