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A Survey and Comparison of PeertoPeer Overlay Network Schemes
 IEEE Communications Surveys and Tutorials
, 2005
"... Abstract — Over the Internet today, computing and communications environments are significantly more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. There has been much interest in emerging PeertoPeer (P2P) network overlays beca ..."
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Cited by 147 (0 self)
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Abstract — Over the Internet today, computing and communications environments are significantly more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. There has been much interest in emerging PeertoPeer (P2P) network overlays because they provide a good substrate for creating largescale data sharing, content distribution and applicationlevel multicast applications. These P2P networks try to provide a long list of features such as: selection of nearby peers, redundant storage, efficient search/location of data items, data permanence or guarantees, hierarchical naming, trust and authentication, and, anonymity. P2P networks potentially offer an efficient routing architecture that is selforganizing, massively scalable, and robust in the widearea, combining fault tolerance, load balancing and explicit notion of locality. In this paper, we present a survey and comparison of various Structured and Unstructured P2P networks. We categorize the various schemes into these two groups in the design spectrum and discuss the applicationlevel network performance of each group.
SmallWorld Phenomena and the Dynamics of Information
 In Advances in Neural Information Processing Systems (NIPS) 14
, 2001
"... Introduction The problem of searching for information in networks like the World Wide Web can be approached in a variety of ways, ranging from centralized indexing schemes to decentralized mechanisms that navigate the underlying network without knowledge of its global structure. The decentralized ap ..."
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Cited by 134 (6 self)
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Introduction The problem of searching for information in networks like the World Wide Web can be approached in a variety of ways, ranging from centralized indexing schemes to decentralized mechanisms that navigate the underlying network without knowledge of its global structure. The decentralized approach appears in a variety of settings: in the behavior of users browsing the Web by following hyperlinks; in the design of focused crawlers [4, 5, 8] and other agents that explore the Web's links to gather information; and in the search protocols underlying decentralized peertopeer systems such as Gnutella [10], Freenet [7], and recent research prototypes [21, 22, 23], through which users can share resources without a central server. In recent work, we have been investigating the problem of decentralized search in large information networks [14, 15]. Our initial motivation was an experiment that dealt directly with the search problem in a decidedly preInternet context: Stanley Milgram
A Local Search Mechanism for PeertoPeer Networks
, 2002
"... One important problem in peertopeer (P2P) networks is searching and retrieving the correct information. However, existing searching mechanisms in pure peertopeer networks are inefficient due to the decentralized nature of such networks. We propose two mechanisms for information retrieval in pure ..."
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Cited by 103 (6 self)
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One important problem in peertopeer (P2P) networks is searching and retrieving the correct information. However, existing searching mechanisms in pure peertopeer networks are inefficient due to the decentralized nature of such networks. We propose two mechanisms for information retrieval in pure peertopeer networks. The first, the modified BreadthFirstSearch (BFS) mechanism, is an extension of the current Gnuttela protocol, allows searching with keywords, and is designed to minimize the number of messages that are needed to search the network. The second, the Intelligent Search mechanism, uses the past behavior of the P2P network to further improve the scalability of the search procedure. In this algorithm, each peer autonomously decides which of its peers are most likely to answer a given query. The algorithm is entirely distributed, and therefore scales well with the size of the network. We implemented our mechanisms as middleware platforms. To show the advantages of our mechanisms we present experimental results using the middleware implementation.
Complex Networks and Decentralized Search Algorithms
 In Proceedings of the International Congress of Mathematicians (ICM
, 2006
"... The study of complex networks has emerged over the past several years as a theme spanning many disciplines, ranging from mathematics and computer science to the social and biological sciences. A significant amount of recent work in this area has focused on the development of random graph models that ..."
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Cited by 73 (1 self)
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The study of complex networks has emerged over the past several years as a theme spanning many disciplines, ranging from mathematics and computer science to the social and biological sciences. A significant amount of recent work in this area has focused on the development of random graph models that capture some of the qualitative properties observed in largescale network data; such models have the potential to help us reason, at a general level, about the ways in which realworld networks are organized. We survey one particular line of network research, concerned with smallworld phenomena and decentralized search algorithms, that illustrates this style of analysis. We begin by describing a wellknown experiment that provided the first empirical basis for the "six degrees of separation" phenomenon in social networks; we then discuss some probabilistic network models motivated by this work, illustrating how these models lead to novel algorithmic and graphtheoretic questions, and how they are supported by recent empirical studies of large social networks.
Faulttolerant Routing in Peertopeer Systems
, 2003
"... We consider the problem of designing an overlay network and routing mechanism that permits finding resources efficiently in a peertopeer system. We argue that many existing approaches to this problem can be modeled as the construction of a random graph embedded in a metric space whose points repre ..."
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Cited by 60 (1 self)
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We consider the problem of designing an overlay network and routing mechanism that permits finding resources efficiently in a peertopeer system. We argue that many existing approaches to this problem can be modeled as the construction of a random graph embedded in a metric space whose points represent resource identifiers, where the probability of a connection between two nodes depends only on the distance between them in the metric space. We study the performance of a peertopeer system where nodes are embedded at grid points in a simple metric space: a onedimensional real line. We prove upper and lower bounds on the message complexity of locating particular resources in such a system, under a variety of assumptions about failures of either nodes or the connections between them. Our lower bounds in particular show that the use of inverse powerlaw distributions in routing, as suggested by Kleinberg [5], is close to optimal. We also give efficient heuristics to dynamically maintain such a system as new nodes arrive and old nodes depart. Finally, we give experimental results that suggest promising directions for future work.
Conductance and Congestion in Power Law Graphs
, 2003
"... It has been observed that the degrees of the topologies of several communication networks follow heavy tailed statistics. What is the impact of such heavy tailed statistics on the performance of basic communication tasks that a network is presumed to support? How does performance scale with the size ..."
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Cited by 57 (3 self)
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It has been observed that the degrees of the topologies of several communication networks follow heavy tailed statistics. What is the impact of such heavy tailed statistics on the performance of basic communication tasks that a network is presumed to support? How does performance scale with the size of the network? We study routing in families of sparse random graphs whose degrees follow heavy tailed distributions. Instantiations of such random graphs have been proposed as models for the topology of the Internet at the level of Autonomous Systems as well as at the level of routers. Let n be the number of nodes. Suppose that for each pair of nodes with degrees du and dv we have O(dudv ) units of demand. Thus the total demand is O(n ). We argue analytically and experimentally that in the considered random graph model such demand patterns can be routed so that the flow through each link is at most O . This is to be compared with a bound # that holds for arbitrary graphs. Similar results were previously known for sparse random regular graphs, a.k.a. "expander graphs." The significance is that Internetlike topologies, which grow in a dynamic, decentralized fashion and appear highly inhomogeneous, can support routing with performance characteristics comparable to those of their regular counterparts, at least under the assumption of uniform demand and capacities. Our proof uses approximation algorithms for multicommodity flow and establishes strong bounds of a generalization of "expansion," namely "conductance." Besides routing, our bounds on conductance have further implications, most notably on the gap between first and second eigenvalues of the stochastic normalization of the adjacency matrix of the graph.
Adding structure to unstructured peertopeer networks: the role of overlay topology
 in Proceedings of Networked Group Communication (NGC
, 2003
"... ..."
Decentralized Search in Networks Using Homophily and Degree Disparity
, 2005
"... We propose a new algorithm for finding a target node in a network whose topology is known only locally. We formulate this task as a problem of decision making under uncertainty and use the statistical properties of the graph to guide this decision. This formulation uses the homophily and degree stru ..."
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Cited by 17 (0 self)
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We propose a new algorithm for finding a target node in a network whose topology is known only locally. We formulate this task as a problem of decision making under uncertainty and use the statistical properties of the graph to guide this decision. This formulation uses the homophily and degree structure of the network simultaneously, differentiating our algorithm from those previously proposed in the literature. Because homophily and degree disparity are characteristics frequently observed in realworld networks, the algorithm we propose is applicable to a wide variety of networks, including two families that have received much recent attention: smallworld and scalefree networks.
On small world graphs in nonuniformly distributed key spaces
 In Proceedings of the 21st International Conference on Data Engineering Workshops (ICDEW
, 2005
"... In this paper we show that the topologies of most logarithmicstyle P2P systems like Pastry, Tapestry or PGrid resemble smallworld graphs. Inspired by Kleinberg’s smallworld model [6] we extend the model of building “routingefficient ” smallworld graphs and propose two new models. We show that ..."
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Cited by 15 (11 self)
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In this paper we show that the topologies of most logarithmicstyle P2P systems like Pastry, Tapestry or PGrid resemble smallworld graphs. Inspired by Kleinberg’s smallworld model [6] we extend the model of building “routingefficient ” smallworld graphs and propose two new models. We show that the graph, constructed according to our model for uniform key distribution and logarithmic outdegree, will have similar properties as the topologies of structured P2P systems with logarithmic outdegree. Moreover, we propose a novel model of building graphs which support uneven node distributions and preserves all desired properties of Kleinberg’s smallworld model. With such a model we are setting a reference base for nowadays emerging P2P systems that need to support uneven key distributions.
SmallWorld Overlay P2P Networks: Construction and Handling Dynamic Flash Crowd
"... In this paper, we consider how to "construct" and "maintain" an overlay structured P2P network based on the "smallworld paradigm". Two main attractive properties of a smallworld network are (1) low average hop distance between any two randomly chosen nodes and, (2) high clustering coefficient. A ne ..."
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Cited by 13 (0 self)
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In this paper, we consider how to "construct" and "maintain" an overlay structured P2P network based on the "smallworld paradigm". Two main attractive properties of a smallworld network are (1) low average hop distance between any two randomly chosen nodes and, (2) high clustering coefficient. A network with a low average hop distance implies a small latency for object lookup. While a network with a high clustering coefficient implies the underlying P2P network has the "potential" to provide object lookup service even in the midst of heavy object traffic loading, for example, under a flash crowd scenario. In this paper, we present the SWOP protocol of constructing a smallworld overlay P2P network. We compare our result with other structured P2P networks such as the Chord protocol. Although the Chord protocol can provide object lookup with latency of 34834 complexity, where is the number of nodes in a P2P network, we show that the SWOP protocol can further improve the object lookup performance. We also take advantage of the high clustering coefficient of a smallworld P2P network and propose an object replication algorithm to handle the heavy object traffic loading situation, e.g. under the dynamic flash crowd scenario. We show that the SWOP network can quickly and efficiently deliver the "popular" and "dynamic" object to all requested nodes. Based on our knowledge, this is the first work that addresses how to handle the "dynamic" flash crowd scenario on a structured P2P network.