We propose a balanced tree structure overlay on a peer-to-peer network capable of supporting both exact queries and range queries efficiently. In spite of the tree structure causing distinctions to be made between nodes at different levels in the tree, we show that the load at each node is approximately equal. In spite of the tree structure providing precisely one path between any pair of nodes, we show that sideways routing tables maintained at each node provide sufficient fault tolerance to permit efficient repair. Specifically, in a network with N nodes, we guarantee that both exact queries and range queries can be answered in O(logN) steps and also that update operations (to both data and network) have an amortized cost of O(logN). An experimental assessment validates the practicality of our proposal. 1

Abstract. Publish/Subscribe systems have become a prevalent model for delivering data from producers (publishers) to consumers (subscribers) distributed across wide-area networks while decoupling the publishers and the subscribers from each other. In this paper we present Meghdoot, which adapts content-based publish/subscribe systems to Distributed Hash Table based P2P networks in order to provide scalable content delivery mechanisms while maintaining the decoupling between the publishers and the subscribers. Meghdoot is designed to adapt to highly skewed data sets, which is typical of real applications. The experimental results demonstrate that Meghdoot balances the load among the peers and the design scales well with increasing number of peers, subscriptions and events. 1

Abstract Peer-to-peer (P2P) networks have become a powerful means for online data exchange. Currently, users are primarily utilizing these networks to perform exact-match queries and retrieve complete files. However, future more data intensive applications, such as P2P auction networks, P2P job-search networks, P2P multi-player games, will require the capability to respond to more complex queries such as range queries involving numerous data types including those that have a spatial component. In this paper, a distributed quadtree index that adapts the MX-CIF quadtree is described that enables more powerful accesses to data in P2P networks. This index has been implemented for various prototype P2P applications and results of experiments are presented. Our index is easy to use, scalable, and exhibits good load-balancing properties. Similar indices can be constructed for various multi-dimensional data types with both spatial and non-spatial components. This work was supported in part by the National Science Foundation under grants EIA-99-00268, EIA-00-91474, and CCF-05-15241 as well as Microsoft Research.

Multi-dimensional data indexing has received much attention in a centralized database. However, not so much work has been done on this topic in the context of Peerto-Peer systems. In this paper, we propose a new Peer-to-Peer framework based on a balanced tree structure overlay, which can support extensible centralized mapping methods and query processing based on a variety of multidimensional tree structures, including R-Tree, X-Tree, SS-Tree, and M-Tree. Specifically, in a network with N nodes, our framework guarantees that point queries and range queries can be answered within O(logN) hops. We also provide an effective load balancing strategy to allow nodes to balance their work load efficiently. An experimental assessment validates the practicality of our proposal. 1.

Peer-to-Peer systems have recently become a popular means to share resources. Effective search is a critical requirement in such systems, and a number of distributed search structures have been proposed in the literature. Most of these structures provide “log time search ” capability, where the logarithm is taken base 2. That is, in a system with N nodes, the cost of the search is O(log2N). In database systems, the importance of large fanout index structures has been well recognized. In P2P search too, the cost could be reduced considerably if this logarithm were taken to a larger base. In this paper, we propose a multiway tree search structure, which reduces the cost of search to O(logmN), where m is the fanout. The penalty paid is a larger update cost, but we show how to keep this penalty to be no worse than linear in m. We experimentally explore this tradeoff between search and update cost as a function of m, and suggest how to find a good trade-off point. The multi-way tree structure we propose, BATON*, is derived from the BATON structure that has recently been suggested. In addition to multi-way fanout, BATON * also adds support for multi-attribute queries to BATON. 1.

Abstract. Peer-to-peer systems offer an efficient means for sharing data among autonomous nodes. A central issue is locating the nodes with data matching a user query. A decentralized solution to this problem is based on using routing indexes which are data structures that describe the content of neighboring nodes. Each node uses its routing index to route a query towards those of its neighbors that provide the largest number of results. We consider using histograms as routing indexes. We describe a decentralized procedure for clustering similar nodes based on histograms. Similarity between nodes is defined based on the set of queries they match and related with the distance between their histograms. Our experimental results show that using histograms to cluster similar nodes and to route queries increases the number of results returned for a given number of nodes visited. 1

Current peer-to-peer (P2P) index structures only support a subset of the desired functionality for P2P database systems. For instance, some P2P index structures support equality queries but not range queries, while others support range queries, but do not support multiple data items per peer or provide guaranteed search performance. In this paper, we devise a novel index structure called P-Ring that supports both equality and range queries, is fault-tolerant, provides guaranteed search performance, and efficiently supports large sets of data items per peer. We are not aware of any other existing index structure that supports all of the above functionality in a dynamic P2P environment. In a thorough experimental study we evaluate the performance of P-Ring and quantify the performance trade-offs of the different system components. We also compare P-Ring with two other P2P index structures, Skip Graphs and Chord. 1.

Recent advances in low-power sensing devices coupled with the widespread availability of wireless ad-hoc networks have fueled the development of sensor networks. These are typically deployed over wide areas to gather data in the environment and monitor events of interest. The ability to run spatial queries is extremely useful for sensor networks. Spatial query execution has been extensively studied in the context of centralized spatial databases; however because of the energy and bandwidth limitation of sensor nodes these solutions are not directly applicable to the sensor network. In this paper we propose a scalable and distributed way of spatial query execution in sensor networks. We develop a distributed spatial index over the sensor nodes that is used in processing spatial queries in a distributed fashion. We evaluate the behavior of our approach and show that our mechanism provides an efficient and scalable way to run spatial queries over sparse and dense sensor networks.

Grid superscheduling requires support for efficient and scalable discovery of resources. Resource discovery activities involve searching for the appropriate resource types that match the user’s job requirements. To accomplish this goal, a resource discovery system that supports the desired look-up operation is mandatory. Various kinds of solutions to this problem have been suggested, including the centralised and hierarchical information server approach. However, both of these approaches have serious limitations in regards to scalability, fault-tolerance and network congestion. To overcome these limitations, organising resource information using Peer-to-Peer (P2P) network model has been proposed. Existing approaches advocate an extension to structured P2P protocols, to support the Grid resource information system (GRIS). In this paper, we identify issues related to the design of such an efficient, scalable, fault-tolerant, consistent and practical GRIS system using a P2P network model. We compile these issues into various taxonomies in sections 3 and 4. Further, we look into existing works that apply P2P based network protocols to GRIS. We think that this taxonomy and its mapping to relevant systems would be useful for academic and industry based researchers who are engaged in the design of scalable Grid systems. 1

Efficient Resource discovery mechanism is one of the fundamental requirement for Grid computing systems, as it aids in resource management and scheduling of applications. Resource discovery activity involve searching for the appropriate resource types that match the user’s application requirements. Various kinds of solutions to grid resource discovery have been suggested, including the centralised and hierarchical information server approach. However, both of these approaches have serious limitations in regards to scalability, fault-tolerance and network congestion. To overcome these limitations, indexing resource information using a decentralised (such as Peer-to-Peer (P2P)) network model has been actively proposed in the past few years. This article investigates various decentralised resource discovery techniques primarily driven by P2P network model. To summarise, this article presents a: (i) summary of current state of art in grid resource discovery; (ii) resource taxonomy with focus on computational grid paradigm; (iii) P2P taxonomy with focus on extending the current structured systems (such as Distributed Hash Tables) for indexing d-dimensional grid resource queries; (iv) detailed survey of existing works that can support d-dimensional grid resource queries; and (v) classification of the surveyed approaches based on the proposed P2P taxonomy. We believe that this taxonomy and its mapping to relevant systems would be useful for academic and industry based researchers who are engaged in the design of scalable Grid and P2P systems. 1