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70
A Tight Bound on Approximating Arbitrary Metrics by Tree Metrics
 In Proceedings of the 35th Annual ACM Symposium on Theory of Computing
, 2003
"... In this paper, we show that any n point metric space can be embedded into a distribution over dominating tree metrics such that the expected stretch of any edge is O(log n). This improves upon the result of Bartal who gave a bound of O(log n log log n). Moreover, our result is existentially tight; t ..."
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Cited by 306 (8 self)
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In this paper, we show that any n point metric space can be embedded into a distribution over dominating tree metrics such that the expected stretch of any edge is O(log n). This improves upon the result of Bartal who gave a bound of O(log n log log n). Moreover, our result is existentially tight; there exist metric spaces where any tree embedding must have distortion#sto n)distortion. This problem lies at the heart of numerous approximation and online algorithms including ones for group Steiner tree, metric labeling, buyatbulk network design and metrical task system. Our result improves the performance guarantees for all of these problems.
A survey of web caching schemes for the internet
 ACM Computer Communication Review
, 1999
"... The World Wide Web can be considered as a large distributed information system that provides access to shared data objects. As one of the most popular applications currently running on the Internet, the World Wide Web is of an exponential growth in size, which results in network congestion and serve ..."
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Cited by 292 (2 self)
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The World Wide Web can be considered as a large distributed information system that provides access to shared data objects. As one of the most popular applications currently running on the Internet, the World Wide Web is of an exponential growth in size, which results in network congestion and server overloading. Web caching has been recognized as one of the effective schemes to alleviate the service bottleneck and reduce the network traffic, thereby minimize the user access latency. In this paper, we first describe the elements of a Web caching system and its desirable properties. Then, we survey the stateofart techniques which have been used in Web caching systems. Finally, we discuss the research frontier
Approximation Algorithms for Data Placement in Arbitrary Networks
, 2001
"... We study approximation algorithms for placing replicated data in arbitrary networks. Consider a network of nodes with individual storage capacities and a metric communication cost function, in which each node periodically issues a request for an object drawn from a collection of uniformlength objec ..."
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Cited by 84 (4 self)
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We study approximation algorithms for placing replicated data in arbitrary networks. Consider a network of nodes with individual storage capacities and a metric communication cost function, in which each node periodically issues a request for an object drawn from a collection of uniformlength objects. We consider the problem of placing copies of the objects among the nodes such that the average access cost is minimized. Our main result is a polynomialtime constantfactor approximation algorithm for this placement problem. Our algorithm is based on a careful rounding of a linear programming relaxation of the problem. We also show that the data placement problem is MAXSNPhard. We extend our approximation result to a generalization of the data placement problem that models additional costs such as the cost of realizing the placement. We also show that when object lengths are nonuniform, a constantfactor approximation is achievable if the capacity at each node in the approximate solution is allowed to exceed that in the optimal solution by the length of the largest object.
Coordinated Placement and Replacement for LargeScale Distributed Caches
 IEEE Transactions on Knowledge and Data Engineering
, 1998
"... In a largescale information system such as a digital library or the web, a set of distributed caches can improve their effectiveness by coordinating their data placement decisions. In this paper, we examine the design space for cooperative placement and replacement algorithms. Our main focus is on ..."
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Cited by 84 (8 self)
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In a largescale information system such as a digital library or the web, a set of distributed caches can improve their effectiveness by coordinating their data placement decisions. In this paper, we examine the design space for cooperative placement and replacement algorithms. Our main focus is on the placement algorithms, which attempt to solve the following problem: given a set of caches, the network distances between caches, and predictions of the access rates from each cache to a set of objects, determine where to place each object in order to minimize the average access cost. Replacement algorithms also attempt to minimize access cost, but they work by selecting which objects to evict when a cache miss occurs. Using simulation, we examine three practical cooperative placement algorithms including one that is provably close to optimal, and we compare these algorithms to the optimal placement algorithm and several cooperative and noncooperative replacement algorithms. We draw fiv...
The Online Median Problem
 In Proceedings of the 41st Annual IEEE Symposium on Foundations of Computer Science
, 2000
"... We introduce a natural variant of the (metric uncapacitated) kmedian problem that we call the online median problem. Whereas the kmedian problem involves optimizing the simultaneous placement of k facilities, the online median problem imposes the following additional constraints: the facilities ar ..."
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Cited by 82 (2 self)
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We introduce a natural variant of the (metric uncapacitated) kmedian problem that we call the online median problem. Whereas the kmedian problem involves optimizing the simultaneous placement of k facilities, the online median problem imposes the following additional constraints: the facilities are placed one at a time; a facility cannot be moved once it is placed, and the total number of facilities to be placed, k, is not known in advance. The objective of an online median algorithm is to minimize the competitive ratio, that is, the worstcase ratio of the cost of an online placement to that of an optimal offline placement. Our main result is a lineartime constantcompetitive algorithm for the online median problem. In addition, we present a related, though substantially simpler, lineartime constantfactor approximation algorithm for the (metric uncapacitated) facility location problem. The latter algorithm is similar in spirit to the recent primaldualbased facility location algorithm of Jain and Vazirani, but our approach is more elementary and yields an improved running time.
Choosing Replica Placement Heuristics for WideArea Systems
 In ICDCS ’04: Proceedings of the 24th International Conference on Distributed Computing Systems (ICDCS’04
, 2004
"... Data replication is used extensively in widearea distributed systems to achieve low dataaccess latency. A large number of heuristics have been proposed to perform replica placement. Practical experience indicates that the choice of heuristic makes a big difference in terms of the cost of required ..."
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Cited by 53 (0 self)
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Data replication is used extensively in widearea distributed systems to achieve low dataaccess latency. A large number of heuristics have been proposed to perform replica placement. Practical experience indicates that the choice of heuristic makes a big difference in terms of the cost of required infrastructure (e.g., storage capacity and network bandwidth), depending on system topology, workload and performance goals.
Do We Need Replica Placement Algorithms in Content Delivery Networks
 In Proceedings of the International Workshop on Web Content Caching and Distribution (WCW
, 2002
"... Numerous replica placement algorithms have been proposed in the literature for use in content delivery networks. However, little has been done to compare the various placement algorithms against each other and against caching. This paper debates whether we need replica placement algorithms in conten ..."
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Cited by 47 (3 self)
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Numerous replica placement algorithms have been proposed in the literature for use in content delivery networks. However, little has been done to compare the various placement algorithms against each other and against caching. This paper debates whether we need replica placement algorithms in content delivery networks or not.
A Framework for Evaluating Replica Placement Algorithms
, 2002
"... This paper introduces a framework for evaluating replica placement algorithms (RPA) for content delivery networks (CDN) as well as RPAs from other fields that might be applicable to current or future CDNs. First, the framework classifies and qualitatively compares RPAs using a generic set of primiti ..."
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Cited by 43 (1 self)
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This paper introduces a framework for evaluating replica placement algorithms (RPA) for content delivery networks (CDN) as well as RPAs from other fields that might be applicable to current or future CDNs. First, the framework classifies and qualitatively compares RPAs using a generic set of primitives that capture problem definitions and heuristics. Second, it provides estimates for the decision times of RPAs using an analytic model. To achieve accuracy, the model takes into account disk accesses and message sizes, in addition to computational complexity and message numbers that have been considered traditionally. Third, it uses the "goodness" of produced placements to compare RPAs even when they have different problem definitions. Based on these evaluations, we identify open issues and potential areas for future research.
CDN: Content Distribution Network
, 2003
"... Internet evolves and operates largely without a central coordination, the lack of which was and is critically important to the rapid growth and evolution of Internet. However, the lack of management in turn makes it very difficult to guarantee proper performance and to deal systematically with perfo ..."
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Cited by 33 (0 self)
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Internet evolves and operates largely without a central coordination, the lack of which was and is critically important to the rapid growth and evolution of Internet. However, the lack of management in turn makes it very difficult to guarantee proper performance and to deal systematically with performance problems. Meanwhile, the available network bandwidth and server capacity continue to be overwhelmed by the skyrocketing Internet utilization and the accelerating growth of bandwidth intensive content. As a result, Internet service quality perceived by customers is largely unpredictable and unsatisfactory. Content Distribution Network (CDN) is an e ective approach to improve Internet service quality. CDN replicates the content from the place of origin to the replica servers scattered over the Internet and serves a request from a replica server close to where the request originates. In this paper, we first give an overview about CDN. We then present the critical issues involved in designing and implementing an effective CDN and survey the approaches proposed in literature to address these problems. An example of CDN is described to show how a real commercial CDN operates. After this, we present a scheme that provides fast service location for peertopeer systems, a special type of CDN with no infrastructure support. We conclude with a brief projection about CDN.
On the Optimization of Storage Capacity Allocation for Content Distribution
 Computer Networks
, 2003
"... The addition of storage capacity in network nodes for the caching or replication of popular data objects results in reduced enduser delay, reduced network tra#c, and improved scalability. ..."
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Cited by 27 (1 self)
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The addition of storage capacity in network nodes for the caching or replication of popular data objects results in reduced enduser delay, reduced network tra#c, and improved scalability.