We present Tapestry, a peer-to-peer overlay routing infrastructure offering efficient, scalable, locationindependent routing of messages directly to nearby copies of an object or service using only localized resources. Tapestry supports a generic Decentralized Object Location and Routing (DOLR) API using a self-repairing, softstate based routing layer. This paper presents the Tapestry architecture, algorithms, and implementation. It explores the behavior of a Tapestry deployment on PlanetLab, a global testbed of approximately 100 machines. Experimental results show that Tapestry exhibits stable behavior and performance as an overlay, despite the instability of the underlying network layers. Several widely-distributed applications have been implemented on Tapestry, illustrating its utility as a deployment infrastructure.

We propose probabilistic location to enhance the performance of existing peer-to-peer location mechanisms in the case where a replica for the queried data item exists close to the query source. We introduce the attenuated Bloom filter, a lossy distributed index. We describe how to use these data structures for document location and how to maintain them despite document motion. We include a detailed performance study which indicates that our algorithm performs as desired, both finding closer replicas and finding them faster than deterministic algorithms alone. I.

Abstract — Most P2P systems that provide a DHT abstraction distribute objects randomly among “peer nodes ” in a way that results in some nodes having times as many objects as the average node. Further imbalance may result due to nonuniform distribution of objects in the identifier space and a high degree of heterogeneity in object loads and node capacities. Additionally, a node’s load may vary greatly over time since the system can be expected to experience continuous insertions and deletions of objects, skewed object arrival patterns, and continuous arrival and departure of nodes. In this paper, we propose an algorithm for load balancing in such heterogeneous, dynamic P2P systems. Our simulation results show that in the face of rapid arrivals and departures of objects of widely varying load, our algorithm achieves load balancing for system utilizations as high as 90 % while moving only about 8 % of the load that arrives into the system. Similarly, in a dynamic system where nodes arrive and depart, our algorithm moves less than 60 % of the load the underlying DHT moves due to node arrivals and departures. Finally, we show that our distributed algorithm performs only negligibly worse than a similar centralized algorithm, and that node heterogeneity helps, not hurts, the scalability of our algorithm. I.

Web caches, content distribution networks, peer-to-peer file sharing networks, distributed file systems, and data grids all have in common that they involve a community of users who generate requests for shared data. In each case, overall system performance can be improved significantly if we can first identify and then exploit interesting structure within a community's access patterns. To this end, we propose a novel perspective on file sharing based on the study of the relationships that form among users based on the files in which they are interested. We propose a new structure that captures common user interests in data---the data-sharing graph--- and justify its utility with studies on three data-distribution systems: a high-energy physics collaboration, the Web, and the Kazaa peer-to-peer network. We find small-world patterns in the data-sharing graphs of all three communities. We analyze these graphs and propose some probable causes for these emergent small-world patterns. The significance of smallworld patterns is twofold: it provides a rigorous support to intuition and, perhaps most importantly, it suggests ways to design mechanisms that exploit these naturally emerging patterns.

In this paper we evaluate a method of using interleaved spanning trees to compose a resilient, high performance overlay mesh. Though spanning trees of arbitrary type could be used to construct an overlay mesh, we focus on a distributed algorithm that computes k minimum spanning trees on an arbitrary graph. The principal motivation behind this strategy is to provide applications with a k-redundant, high quality mesh suitable for demanding applications like A/V broadcast, video conferencing, data collection, multi-path routing, and file mirroring/transfer. We elaborate details of k-MST, pointing out advantages and potential problem points of the protocol, and then analyze its performance using a variety of metrics with simulation as well as a functional PlanetLab implementation.

Abstract. In this work we study how to process complex queries in DHT-based Peer-to-Peer (P2P) data networks. Queries are made over tuples and relations and are expressed in a query language, such as SQL. We describe existing research approaches for query processing in P2P systems, we suggest improvements and enhancements, and propose a unifying framework that consists of a modified DHT architecture, data placement and search algorithms, and provides efficient support for processing a variety of query types, including queries with one or more attributes, queries with selection operators (involving equality and range queries), and queries with join operators. To our knowledge, this is the first work that puts forth a framework providing support for all these query types. 1

P2P systems inherently have high scalability, robustness and fault tolerance because there is no centralized server and the network self-organizes itself. This is achieved at the cost of higher latency for locating the resources of interest in the P2P overlay network. Internet telephony can be viewed as an application of P2P architecture where the participants form a self-organizing P2P overlay network to locate and communicate with other participants. We propose a pure P2P architecture for the Session Initiation Protocol (SIP)-based IP telephony systems. Our P2P-SIP architecture supports basic user registration and call setup as well as advanced services such as offline message delivery, voice/video mails and multi-party conferencing.

Abstract. P2P-based applications like file-sharing or distributed storage benefit from the scalability and performance of completely decentralized P2P infrastructures. However, existing P2P infrastructures like Chord or Pastry are vulnerable against selfish and malicious behavior and provide currently little support for commercial applications. There is a need for reliable mechanisms that enable the commercial use of P2P technology, while maintaining favorable scalability properties. PeerMint is a completely decentralized and secure accounting scheme which facilitates market-based management of P2P applications. The scheme applies a structured P2P overlay network to keep accounting information in an efficient and reliable way. Session mediation peers are used to minimize the impact of collusion among peers. A prototype has been implemented as part of a modular Accounting and Charging system to show PeerMint’s practical applicability. Experiments were performed to provide evidence of the scheme’s scalability and reliability. 1

Many Peer-to-peer (P2P) applications such as media broadcasting and content distribution require a high performance overlay structure in order to deliver satisfying quality of service (QoS). Previous approaches to building such overlays either involve a shared contact point, which results in non-scalable solutions, or rely on gossip style membership dissemination, which lacks QoS awareness. In this paper, we present a distributed membership service called RandPeer, which manages membership information on behalf of P2P applications, and allows peers to locate good neighbors based on their QoS characteristics. Using this service, P2P applications can easily construct their overlays in a scalable and QoS aware fashion. We have implemented RandPeer and experimented in both local and wide area environments. Our results show that (1) RandPeer is scalable and robust to highly dynamic P2P memberships; (2) RandPeer has good lookup performance, both in terms of response time and the randomness of peer selection. The latter improves load balancing and failure resilience of P2P applications; (3) when used to improve the performance of a mesh based P2P overlay, RandPeer achieves 10 % improvement in just 2 protocol rounds, which is more than 5 times faster than pure random neighbor selections. 1

Sensor networks consist of a potentially huge number of very small and resource limited self-organizing devices. This paper presents the design of a general distributed service directory architecture for sensor networks which especially focuses on the security issues in sensor networks. It ensures secure construction and maintenance of the underlying storage structure, a Content Addressable Network. It also considers integrity of the distributed service directory and secures communication between service provider and inquirer using self-certifying path names. Key area of application of this architecture are gradually extendable sensor networks where sensors and actuators jointly perform various user defined tasks, e.g., in the field of an office environment.