Skip Tree Graph: a Distributed and Balanced Search Tree for Peer-to-Peer Networks (original) (raw)
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Distributed deterministic 1–2 skip list for peer-to-peer system
Data management in the peer-to-peer system is a challenging task due to the random distribution of data among several participating peers. Efficient data structures like distributed hash tables (DHT) and its variants are designed and implemented to reduce the complexity of data management in such environment. However, DHT has its limitations in supporting range queries and its variants like distributed segment trees often perform poorly when the number of peers is high. Further, distributed lists and distributed balanced trees require significant amount of time for stabilizing after a new peer joins or a peer leaves. In this paper, a new distributed data structure called determin-istic 1–2 skip list is introduced as an alternate solution for data management in the peer-to-peer systems. A determin-istic skip list can be viewed as an alternate of a balanced tree, where the semantic locality of each key is preserved. Thus it can support the range queries as well as the single shot queries. This paper proposes three main operations on this data structure-searching data based on keys, insertion when a new peer joins, and deletion when a peer leaves. The correctness of the proposed operations are analyzed using theoretical arguments and mathematical proofs. The A preliminary version of this work appears in the proceedings of proposed scheme is simulated using NS-2.34 network sim-ulator, and the efficiency of the scheme has been compared with DHT, DST, distributed list and distributed tree based data management. Keywords Deterministic skip list · 1–2 skip list · Data structure · Range queries
Range queries over skip tree graphs
Computer Communications, 2008
The support for complex queries, such as range, prefix and aggregation queries, over structured peer-to-peer systems is currently an active and significant topic of research. This paper demonstrates how Skip Tree Graph, as a novel structure, presents an efficient solution to that problem area through provision of a distributed search tree functionality on decentralised and dynamic environments. Since Skip Tree Graph is based on skip trees, a concurrent approach to skip lists, it constitutes an augmentation of skip graphs that extends its functionality and allows for important performance improvements. This work presents a thorough comparison between these two related peer-to-peer overlay networks, their construction, search algorithms and properties. Being based on tree structures, skip tree graphs supports aggregation queries and multicast/broadcast operations, which cannot be directly implemented in its predecessor. The repair mechanism for healing the structure in case of failures is more efficient and harnesses the parallelism inherent in P2P networks. Particular consideration is given to the performance of different range-query schemes over the two related structures. Theoretical and experimental results conclude that Skip Tree Graphs outperform skip graphs on both exact-match and range searches.
2004 International Workshop on Hot Topics in Peer-to-Peer Systems, 2004
The main contributions are an extensive use of randomization techniques and a novel usage of tree-data structure. The combination of these two ingredients allows a great flexibility of network parameters, such as: load balance among the peers, fast lookups and reduced memory usage. For instance, with routing tables of size (d − 1) log d n, the average number of hops for a lookup is of the order of 1 d ((d − 1) log d n + 1), where n is the number of peers in the network and d is the ariety of the tree data structure. Further, we propose a few new optimization mechanisms that can be adopted in DHT. Extensive simulations support these results.
Scalable Chord-based, Cluster-enhanced Peer-to-Peer Architecture supporting Range Queries
mail.cs.pub.ro
Over the Internet today, computing and communications environments are more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. Peer-to-Peer network overlays provide a good substrate for creating large-scale data sharing, content distribution and application-level multicast applications. We present a scalable, cluster-enhanced P2P overlay network designed to share large sets of replicated distributed objects in the context of large-scale highly dynamic infrastructures. The system extends an existing architecture with an original solution designed to achieve optimal implementation results for range queries, as well as provide a fault-tolerant substrate. It also optimizes message routing in hop-count and throughput, whilst providing an adequate consistency among replicas.
3 nuts : A Locality-Aware Peer-to-Peer Network Combining Random Networks , Search Trees , and DHTs
2009
Categorizing peer-to-peer networks from an algorithmic point of view the two extremes of the spectrum are unstructured networks and networks based on plain distributed hash tables (DHT). Unstructured networks stand out with their simplicity, robustness, and support for complex queries. Though, they lack efficient query algorithms providing guarantees. On the other hand, DHT based networks feature efficient lookup algorithms with typically logarithmic hop distance and provide simple and efficient load balancing. Yet, they are limited to exact match queries and in many cases hard to maintain under churn. In this paper we introduce the 3nuts peer-to-peer network. The aim of 3nuts is to combine unstructured networks and DHTs to overcome their individual shortcomings. This is achieved by cleverly combining self maintaining random networks for robustness, a search tree to allow range queries, and DHTs for load balancing. All network operations in 3nuts are local and distributed, i.e. simp...
Efficient Search in Structured Peer-to-Peer Systems: Binary v.s. K-Ary Unbalanced Tree Structures
Lecture Notes in Computer Science, 2004
We investigate the search cost in terms of number of messages generated for routing queries in tree-based P2P structured systems including binary and k-ary tree structures with different arities and different degrees of imbalance in the tree shape. This work is motivated by the fact that k-ary balanced tree access structures can greatly reduce the number of hops for searching compared to the binary trees. We study to what extent the same fact is true when the tree-like structures for access in P2P environments are unbalanced. Another important issue related to P2P environments is how to build these structures in a self-organizing way. We propose a mechanism for constructing k-ary tree based decentralized access structure in a self-organizing way and based on local interactions only. The ability to search efficiently also on unbalanced k-ary trees opens interesting opportunities for load balancing as has been shown in earlier work on P-Grid, our approach to structured P2P systems.
Dynamic storage and access load balancing for answering range queries in peer-to-peer networks
2011
Recently, many applications have used Peer-to-Peer (P2P) systems to overcome the current problems with client/server systems such as non-scalability, high bandwidth requirement and single point of failure. In this paper, we propose an efficient scheme to support efficient range query processing over structured P2P systems, while balancing both the storage load and access load. The paper proposes a rotating token scheme to balance the storage load by placing joining nodes in appropriate locations in the identifier space to share loads with already overloaded nodes. Then, to support range queries, we utilize an orderpreserving mapping function to map keys to nodes in order preserving way and without hashing. This may result in an access load imbalance due to non-uniform distribution of keys in the identifier space. Thus, we propose an adaptive replication scheme to relieve overloaded nodes by shedding some load on other nodes to balance the access load. We derive a formula for estimating the overhead of the proposed adaptive replication scheme. In this study, we carry simulation experiments with synthetic data to measure the performance of the proposed schemes. Our simulation experiments show significant gains in both storage load balancing and access load balancing.
Brushwood: Distributed Trees in Peer-to-Peer Systems
2005
There is an increasing demand for locality-preserving distribution of complex data structures in peer-to-peer systems. Current systems either do not preserve object locality or suffer from imbalances in data distribution, routing state, and/or query processing costs. In this position paper, we take a systematic approach that enables the deployment of searchable tree structures in p2p environments. We achieve distributed tree traversal with efficient routing distance and routing state. We show how to implement several p2p applications using distributed tree structures.
Optimized Range Queries for Large Scale Networks
2012 IEEE 26th International Conference on Advanced Information Networking and Applications, 2012
Distributed Hash Tables (DHTs) provide the substrate to build scalable and efficient Peer-to-Peer (P2P) networks: distributed systems with the potential to handle massive amounts of data on a very large scale. However, traditional DHTs provide very poor support for range queries. In this article we present a search mechanism that efficiently supports range queries over a ring-like DHT structure using a prefix tree index. Load balancing is improved by delegating the routing of queries to the nodes that store data, and by updating neighbor information through an optimistic approach. Our solution reduces latency and message traffic in environments where queries are more frequent than data insertion operations. We evaluate the performance of the system through simulations and show that our solution in not affected by data skewness.
GRaSP: Generalized Range Search in Peer-to-peer Networks
Proceedings of the Third International ICST Conference on Scalable Information Systems, 2008
We present a framework for generalized range search on trie-structured P2P networks, such as P-Grid. Our techniques exploit hitherto unknown properties of randomized tries. We prove that a P-Grid like network has routing diameter O(log n) with high probability, as well as O(log n) congestion, regardless of the shape of the underlying trie. Based on these properties, we propose GRaSP, a simple scheme for handling arbitrary range search problems, with search and update hop latency O(log n) with high probability. We then apply GRaSP on two range search problems: multidimensional range search over points and rectangles, and three-sided search. Our empirical results show that GRaSP delivers excellent search performance and exhibits very good scalability under heavy load. With respect to three-sided search, our proposed scheme is distinguished in that it attempts to improve load balancing by introducing redundancy via the choice of search space.