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Peer-to-peer systems (p2p) are highly dynamic in nature. They may consist of millions of peers joining only for a limited period of time, resulting in hundreds of join and leave events per second. In this paper we introduce eQuus, a novel distributed hash table (DHT) suitable for highly dynamic environments. eQuus guarantees that lookups are always fast - in terms of both the delay and the total number...
This paper presents GosSkip, a self organizing and fully distributed overlay that provides a scalable support to data storage and retrieval in dynamic environments. The structure of GosSkip, while initially possibly chaotic, eventually matches a perfect set of Skip-list-like structures, where no hash is used on data attributes, thus preserving semantic locality and permitting range queries. The use...
P2P systems that rely on the voluntary contribution of bandwidth by the individual peers may suffer from free riding. To address this problem, mechanisms enforcing fairness in bandwidth sharing have been designed, usually by limiting the download bandwidth to the available upload bandwidth. As in real environments the latter is much smaller than the former, these mechanisms severely affect the download...
The performance of peer-to-peer (P2P) content distribution networks depends highly on the coordination of the peers. Sophisticated cooperation strategies, such as the multiple source download, are the foundation for efficient file exchange. The detailed performance of the strategies are determined by the peer characteristics and the peer behaviour, such as the number of parallel upload connections,...
Bandwidth trading schemes give peers an incentive to provide upload bandwidth to other peers in a P2P network for fast file distribution. A popular example is the tit-for-tat strategy used in the BitTorrent protocol. Although this game theoretical scheme provides an incentive to peers to contribute resources to the network it does not prevent unfairness and the performances of peers vary considerably...
Locality sensitive hash (LSH) is widely used in peer-to-peer (P2P) systems. Although it can support range or similarity queries, it breaks the load balance mechanism of traditional distributed hash table (DHT) based system by replacing consistent hash with LSH. To solve the imbalance problem, current systems either weaken the locality preserve ability from similarity preserved to order preserved or...
To achieve higher efficiency over their unstructured counterparts, structured peer-to-peer systems hold each node responsible for serving a specified set of keys and correctly routing lookups. Unfortunately, malicious participants can abuse these responsibilities to deny access to a set of keys or misroute lookups. We look to address both of these problems through replica placement. Using Chord as...
We present a simple yet novel technique for prefix search in P2P networks. The idea is to extract characters and their position information in a keyword to index objects. Our index scheme can achieve quite balanced loads, avoid hop-spots and single point of failure, reduce storage and maintenance costs, and offer some ranking mechanisms for matching objects. We use 2.412.613 CD records collected in...
Peer discovery and route set-up are an integral part of the processes by which anonymizing peer-to-peer systems are made secure. When systems are large, and individual nodes only gain random knowledge of part of the network, their traffic can be detected by the uniqueness of the information they have learnt. We discuss this problem, which occurred in the initial design of Tarzan, and other related...
The advent and popularity of the World Wide Web (WWW) has enabled access to a variety of semi-structured data and, when available, this data follows some common XML schema. On the other hand the distribution of content has made centralized solutions inappropriate, entering the era of peer-to-peer (P2P) computing, where content is stored in XML databases residing on peers. In this paper, we propose...
This paper addresses overlay topology mismatching problem by presenting "AM", an effective way to measure nodes' relative distance and a technique called "CTAG" to construct topology-aware Gnutella overlay. The approach excels in sending no extra messages to probe the target nodes, avoiding the extra traffic and delay time, while keeping the necessary accuracy
Social applications associate a set of user defined keywords named tags when publishing social objects in order to locate them later. We propose T-DHT, a hybrid unstructured-structured DHT based approach, to cope with the high demanding requirements of social applications, in a fully scalable, distributed and balanced way. T-DHT behaves as a structured DHT when publishing "tag, social-object"...
Large-scale distributed data management with P2P systems requires the existence of similarity operators for queries as we cannot assume that all users agree on exactly the same schema and value representations and data quality problems due to spelling errors and typos. In this paper, we present an approach for efficient processing of similarity selections and joins in a structured overlay. We show...
Peers in peer-to-peer file-sharing systems use conjunctive queries as a way of controlling query cost in the absence of information about the behavior of other peers. Conjunctive queries are good at increasing the precision of query result sets, but may be overly selective, decreasing overall performance. We consider relaxing the conjunctive matching criterion and its impact on performance and cost...
Given some of the recent advances in distributed hash table (DHT) based peer-to-peer (P2P) systems we ask the following questions: are there applications where unstructured queries are still necessary (i.e., the underlying queries do not efficiently map onto any structured framework), and are there unstructured P2P systems that can deliver the high bandwidth and computing performance necessary to...
Within computational grids, some services (software components, linear algebra libraries, etc.) are made available by some servers to some clients. In spite of the growing popularity of such grids, the service discovery, although efficient in many cases, does not reach several requirements. Among them, the flexibility of the discovery and its efficiency on wide-area dynamic platforms are two major...
Recently there has been an increasing interest to harness the potential of P2P technology to design and build rich environments where services are provided and multiple applications can be supported in a flexible and dynamic manner. In such a context, resource assignment to services and applications is crucial. Current approaches require significant "manual-mode" operations and/or rely on...
We propose a decoupled distribution paradigm for connecting large numbers of content publishers and consumers called implicit group messaging (IGM). Unlike traditional multicast or publish/subscribe messaging, IGM delivers content to "implicit groups" of consumers matching combinations of attributes specified by the publisher at the time of publication. The contributions of this paper include...
Content storage in a distributed collaborative environment uses redundancy for better resilience and thus provides good availability and durability. In a peer-to-peer environment, where peers continuously leave and rejoin the network, various lazy strategies can be employed to maintain a minimal redundancy of stored content in the system. Existing static resilience analyses fail to capture in detail...
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