Usage of Kd-Tree in DHT-Based Indexing Scheme

Concurrency and Computation: Practice and Experience, 2011

are scalable, self-organizing, and adaptive to underlying topology changes, thus being a promising infrastructure for hosting large-scale distributed applications. The ever-wider use of DHT infrastructures has found more and more applications that require support for range queries. Recently, a number of DHT-based range query schemes have been proposed. However, most of them suffer from high query delay or imbalanced load distribution. To address these problems, in this paper we first present an efficient indexing structure called Balanced Kautz (BK) tree that uniformly maps the m-dimensional data space onto DHT nodes, and then propose a BK tree-based range query scheme called ERQ that processes range queries in a parallel fashion and guarantees to return the results in a bounded delay. In a DHT with N nodes, ERQ can answer any range of query in less than log N (2 log log N +1) hops in a load-balanced manner, irrespective of the queried range, the whole space size, or the number of queried attributes. The effectiveness of our proposals is demonstrated through experiments.

2007

This paper describes the design and implementation of DAST, a Distributed Arbitrary Segment Tree structure that gives support of range query for public Distributed Hash Table (DHT) services. DAST does not modify the underlying DHT infrastructure, instead it utilises the scalability and robustness of DHT while providing simplicity of implementation and deployment for applications. Compared with traditional segment trees, the arbitrary segment tree used by a DAST reduces the number of key-space segments that need to be ...

2009 29th IEEE International Conference on Distributed Computing Systems, 2009

In this paper, we study the problem of indexing multidimensional data in the P2P networks based on distributed hash tables (DHTs). We identify several design issues and propose a novel over-DHT indexing scheme called m-LIGHT. To preserve data locality, m-LIGHT employs a clever naming mechanism that gracefully maps the index tree into the underlying DHT so that it achieves efficient index maintenance and query processing. Moreover, m-LIGHT leverages a new data-aware index splitting strategy to achieve optimal load balance among peer nodes. We conduct an extensive performance evaluation for m-LIGHT. Compared to the state-of-the-art indexing schemes, m-LIGHT substantially saves the index maintenance overhead, achieves a more balanced load distribution, and improves the range query performance in both bandwidth consumption and response latency.

2011

Distributed Hash Tables (DHTs) provide the substrate to build large scale distributed applications over Peer-to-Peer networks. A major limitation of DHTs is that they only support exact-match queries. In order to offer range queries over a DHT it is necessary to build additional indexing structures. Prefix-based indexes, such as Prefix Hash Tree (PHT), are interesting approaches for building distributed indexes on top of DHTs. Nevertheless, the lookup operation of these indexes usually generates a high amount of unnecessary traffic overhead which degrades system performance by increasing response time. In this paper, we propose a novel distributed cache system called Tabu Prefix , aiming at improving the performance of the Prefix-trees. We have implemented our solution over PHT, and the results confirm that our approach outperforms traditional existing cache solutions for prefix-tree structures.

ABSTRACT Massively distributed applications require the integration of heterogeneous data from multiple sources. Peer-to-peer (P2P) is one possible network model for these distributed applications and among P2P architectures, distributed hash table (DHT) is well known for its routing performance guarantees.

2006

Range query, which is defined as to find all the keys in a certain range over the underlying P2P network, has received a lot of research attentions recently. However, cover query, which is to find all the ranges currently in the system that cover a given key, is rarely touched. In this paper, we first identify that cover query is a highly desired functionality by some popular P2P applications, and then propose distributed segment tree (DST), a layered DHT structure that incorporates the concept of segment tree. Due to the intrinsic capability of segment tree in maintaining the sturcture of ranges, DST is shown to be very efficient for supporting both range query and cover query in a uniform way. It also possesses excellent parallelizability in query operations and can achieve O(1) complexity for moderate query ranges. To balance the load among DHT nodes, we design a downward load stripping mechanism that controls tradeoffs between load and performance. We implemented DST on publicly available OpenDHT service and performed extensive real experiments. All the results and comparisons demonstrate the effectiveness of DST for several important metrics.

2007

In this paper we define a Distributed Arbitrary Segment Tree (DAST), a distributed tree-like structure that layers the range query processing mechanism over public Distributed Hash Table (DHT) services. Compared with traditional segment trees, the arbitrary segment tree used by a DAST reduces the number of key-space segments that need to be maintained, which in turn results in fewer query operations and lower overheads. Moreover, considering that range queries often contain redundant entries that the clients do not need, we ...

2007 IEEE 18th International Symposium on Personal, Indoor and Mobile Radio Communications, 2007

In this paper we define a Distributed Arbitrary Segment Tree (DAST), a distributed tree-like structure that layers the range query processing mechanism over public Distributed Hash DHT) services. Compared with traditional segment trees, the arbitrary segment tree used by a DAST reduces the number of key-space segments that need to be maintained, which in turn results in fewer query operations and lower overheads. Moreover, considering that range queries often contain redundant entries that the clients do not need, we introduce the concept of Accuracy of Results (AoR) for range queries. We demonstrate that by adjusting AoR, the DHT operational overhead can be improved. DAST is implemented on a well-known public DHT service (OpenDHT) and validation through experimentation and supporting simulation is performed. The results demonstrate the effectiveness of DAST over exiting methods.

International Journal of Computer Applications, 2013

Nowadays, DHT-based P2P technology is used as a basis in many wide spread applications because of its scalability, robustness, and load balance. Many applications, including file sharing, communication and live video streaming are in a large distributed network environment. For an efficient and effective search in large data repositories, complex query processing becomes a major issue for DHT. Towards the goal of supporting complex queries in DHT-based P2P systems, this paper focuses on the usage of k-dimensional tree to build a tree-based index. The proposed index is built without modifying the structure of the overlay network. In this paper, the load balancing among peers is also considered according to the usage of kd-tree. Therefore the performance of kd-tree is studied and show that how it can affect the proposed index over P2P network. In this paper, PlanetSim simulator is used to implement the proposed index and evaluate the performance of the index by using various metrics.

2011

Abstract Traditional DHT structures provide very poor support for range queries, since uniform hashing destroys data locality. Several schemes have been proposed to overcome this issue, but they fail to combine load balancing, low message overhead, and low latency in search operations. In this article we present DRing, an efficient layered solution that directly supports range queries over a ring-like DHT structure.