Hash tables – which map “keys ” onto “values” – are an essential building block in modern software systems. We believe a similar functionality would be equally valuable to large distributed systems. In this paper, we introduce the concept of a Content-Addressable Network (CAN) as a distributed infrastructure that provides hash table-like functionality on Internet-like scales. The CAN is scalable, fault-tolerant and completely self-organizing, and we demonstrate its scalability, robustness and low-latency properties through simulation.

We propose a new approach for constructing P2P networks based on a dynamic decomposition of a continuous space into cells corresponding to processors. We demonstrate the power of these design rules by suggesting two new architectures, one for DHT (Distributed Hash Table) and the other for dynamic expander networks. The DHT network, which we call Distance Halving, allows logarithmic routing and load, while preserving constant degrees. Our second construction builds a network that is guaranteed to be an expander. The resulting topologies are simple to maintain and implement. Their simplicity makes it easy to modify and add protocols. We show it is possible to reduce the dilation and the load of the DHT with a small increase of the degree. We present a provably good protocol for relieving hot spots and a construction with high fault tolerance. Finally we show that, using our approach, it is possible to construct any family of constant degree graphs in a dynamic environment, though with worst parameters. Therefore we expect that more distributed data structures could be designed and implemented in a dynamic environment.

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In a Peer-To-Peer (P2P) system, autonomous computers pool their resources (e.g., les, storage, compute cycles) in order to inexpensively handle tasks that would normally require large costly servers. The scale of these systems, their \open nature", and the lack of centralized control pose dicult performance and security challenges. Much research has recently focused on tackling some of these challenges

this paper, we provide a localized estimation scheme that has good worst case accuracy. The scheme requires each joining node to communicate only with two nodes, its initial contact and one additional node. The expected accuracy of our estimator is within the range n=2::n , provided that the joiners' contact points are assigned at random

A number of Distributed Hash Table (DHT)-based protocols have been proposed to address the issue of scalability in peer-topeer networks. However, it remains an open question whether there exists a DHT scheme that can achieve the theoretical lower bound of log log n on network diameter when the average routing table size at nodes is no more than log n. In this paper, we present Ulysses, a peer-to-peer network based on the butterfly topology that matches this theoretical lower bound. Compared to existing DHT-based schemes with similar routing table size, Ulysses reduces the network diameter by a factor of log log n, which is 2-4 for typical configurations. This translates into the same amount of reduction on query latency and average traffic per link/node. In addition, Ulysses maintains the same level of robustness in terms of routing in the face of faults and recovering from graceful/ungraceful joins/departures, as provided by existing DHT-based schemes. The protocol is formally verified for its correctness and robustness using techniques from distributed computing. The performance of the protocol has been evaluated using both analysis and simulation.

Bluetooth is a promising recent radio technology for ad hoc networking. Bluetooth networks are based on connecting together piconets, to form a scatternet. The structure of the scatternet, and the way the scatternet is built and maintained, are not part of the Bluetooth specifications, but have a tremendous impact on the performance of the network. We present an efficient distributed algorithm for Bluetooth scatternet construction. The resulting scatternet is scalable and our construction is dynamic in the sense that nodes can join and leave the network at their convenience. For fixed constant degree of nodes, the resulting diameter is polylogarithmic in the size of the network, and the connectivity of the masters is high. We also give a routing protocol adapted to the specific scatternet topology returned by our algorithm. This protocol does not require complicated path-discovery methods, but is based on a simple virtual labeling of the devices participating in the scatternet.

Different structures are used in peer-to-peer networks to represent their inherently distributed, self-organized and decentralized memory structure. In this paper, a simple rangequeriable distributed data structure, called RAQ, is proposed to efficiently support exact match and range queries over multi-dimensional data. In RAQ, the key space is partitioned among the network with n nodes, in which each element has links to O(log n) other elements. We will show that the look-up query for a specified key can be done via O(log n) message passing. In addition, RAQ handles range-queries in at most O(log n) communication steps. We also present a probabilistic variation of RAQ in which each node has O(log log n) links on the average and look up and range queries are resolved with O(log 2 n) latency. At the end we evaluate RAQ through simulation. 1

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