Search

By combining an unstructured protocol with a DHT-based global index, hybrid peer-to-peer (P2P) improves search efficiency in terms of query recall and response time. The major challenge in hybrid search is how to estimate the number of peers that can answer a given query. Existing approaches assume that such a number can be directly obtained by computing item popularity. In this work, we show that such an assumption is not always valid, and previous designs cannot distinguish whether items related to a query are distributed in many peers or are in a few peers. To address this issue, we propose QRank, a difficulty-aware hybrid search, which ranks queries by weighting keywords based on term frequency. Using rank values, QRank selects proper search strategies for queries. We conduct comprehensive trace-driven simulations to evaluate this design. Results show that QRank significantly improves the search quality as well as reducing system traffic cost compared with existing approaches. [ABSTRACT FROM AUTHOR]

Most trust models in Peer-to-Peer (P2P) systems are identity based, which means that in order for one peer to trust another, it needs to know the other peer's identity. Hence, there exists an inherent trade-off between trust and anonymity. To the best of our knowledge, there is currently no P2P protocol that provides complete mutual anonymity as well as authentication and trust management. We propose a zero-knowledge authentication scheme called Pseudo Trust (PT), where each peer, instead of using its real identity, generates an unforgeable and verifiable pseudonym using a one-way hash function. A novel authentication scheme based on Zero-Knowledge Proof is designed so that peers can be authenticated without leaking any sensitive information. With the help of PT, most existing identity-based trust management schemes become applicable in mutual anonymous P2P systems. We analyze the security and the anonymity in PT and evaluate its performance using trace-driven simulations and a prototype PT-enabled P2P network. The strengths of our design include the following: 1) no need for a centralized trusted party or Certificate Authority (CA); 2) high scalability and security; 3)low traffic and cryptography processing overheads; and 4) man-in-the-middle-attacks resistance. [ABSTRACT FROM AUTHOR]

In order to provide scalable live streaming services, we propose an Interoverlay Optimization scheme, IOO. Instead of selecting better paths in the same overlay, IOO constructs efficient paths using peers in different overlays so as to 1) improve global resource utilization of peer-to-peer (P2P) streaming networks, 2) assign resources based on their locality and delay, 3) guarantee streaming service quality by using the nearest peers, even when such peers might belong to different overlays, and 4) balance the load among the group (streaming overlay) members. We compare the performance of IOO with existing approaches through trace-driven simulations. Results show that IOO outperforms previous schemes in terms of resource utilization and the quality of service (QoS) of streaming services. The IOO scheme has been implemented in an Internet-based live streaming system, called AnySee. AnySee was successfully released in the summer of 2004 in the China Educational Research Network (CERNET). More than 60,000 users enjoy massive entertainment programs, including TV programs, movies, and academic conferences videos. [ABSTRACT FROM AUTHOR]

The Peer-to-Peer (P2P) model, being widely adopted in today's Internet computing, suffers from the problem of topology mismatch between the overlay networks and the underlying physical network. Traditional topology optimization techniques identify physically closer nodes to connect as overlay neighbors, but could significantly shrink the search scope. Recent efforts have been made to address the mismatch problem without sacrificing the search scope, but they either need time synchronization among peers or have a low convergent speed. In this paper, we propose a scalable bipartite overlay (SBO) scheme to optimize the overlay topology by identifying and replacing the mismatched connections. In SBO, we employ an efficient strategy for distributing optimization tasks in peers with different colors. We conducted comprehensive simulations to evaluate this design. The results show that SBO achieves approximately 85 percent of reduction on traffic cost and about 60 percent of reduction on query response time. Our comparisons with previous approaches to address the topology mismatch problem have shown that SBO can achieve a fast convergent speed, without the need of time synchronization among peers. [ABSTRACT FROM AUTHOR]

In unstructured peer-to-peer (P2P) systems, the mechanism of a peer randomly joining and leaving a P2P network causes a topology mismatch between the P2P logical overlay network and the physical underlying network, incurring a large volume of redundant traffic in the Internet. In order to alleviate the topology mismatch problem, we propose Adaptive Connection Establishment (ACE), an algorithm for building an overlay multicast tree among each source node and the peers within a certain diameter from the source peer and further optimizing the neighbor connections that are not on the tree while retaining the search scope. Our simulation study shows that this approach can effectively solve the mismatch problem and significantly reduce P2P traffic. We further study the trade-offs between the topology optimization rate and the information exchange overhead by changing the diameter used to build the tree. [ABSTRACT FROM AUTHOR]

Peer-to-Peer multikeyword searching requires distributed intersection/union operations across wide area networks, raising a large amount of traffic cost. Existing schemes commonly utilize Bloom Filters (BFs) encoding to effectively reduce the traffic cost during the intersection/union operations. In this paper, we address the problem of optimizing the settings of a BF. We show, through mathematical proof, that the optimal setting of BF in terms of traffic cost is determined by the statistical information of the involved inverted lists, not the minimized false positive rate as claimed by previous studies. Through numerical analysis, we demonstrate how to obtain optimal settings. To better evaluate the performance of this design, we conduct comprehensive simulations on TREC WT10G test collection and query logs of a major commercial web search engine. Results show that our design significantly reduces the search traffic and latency of the existing approaches. [ABSTRACT FROM AUTHOR]

Efficient and effective full-text retrieval in unstructured peer-to-peer networks remains a challenge in the research community. First, it is difficult, if not impossible, for unstructured P2P systems to effectively locate items with guaranteed recall. Second, existing schemes to improve search success rate often rely on replicating a large number of item replicas across the wide area network, incurring a large amount of communication and storage costs. In this paper, we propose BloomCast, an efficient and effective full-text retrieval scheme, in unstructured P2P networks. By leveraging a hybrid P2P protocol, BloomCast replicates the items uniformly at random across the P2P networks, achieving a guaranteed recall at a communication cost of O(\sqrtN), where N is the size of the network. Furthermore, by casting Bloom Filters instead of the raw documents across the network, BloomCast significantly reduces the communication and storage costs for replication. We demonstrate the power of BloomCast design through both mathematical proof and comprehensive simulations based on the query logs from a major commercial search engine and NIST TREC WT10G data collection. Results show that BloomCast achieves an average query recall of 91 percent, which outperforms the existing WP algorithm by 18 percent, while BloomCast greatly reduces the search latency for query processing by 57 percent. [ABSTRACT FROM PUBLISHER]

Abstract: In a hybrid peer-to-peer (P2P) system, flooding and DHT are both employed for content locating. The decision to use flooding or DHT largely depends on the population of desired data. Previous works either use local information only, or do not consider dynamic factors of P2P systems. In this paper, we propose a Popularity Adaptive Search method for Hybrid (PASH) protocol. By dynamically estimating the content popularity, PASH properly selects search methods so as to efficiently saves query traffic cost and response time. We evaluate PASH through synthetic and trace-driven simulations. The results show that PASH outperforms existing approaches and it also scales well. [Copyright &y& Elsevier]