DHT-based P2P Systems Research Articles

Tree-based Indexing for DHT-based P2P Systems

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.

An Effective Load Balancing Algorithm for Structured P2P Networks

In DHT based P2P systems, various issues such as peer heterogeneity,network topology, and diverse file popularity, may affect the DHT system efficiency. A new load balance algorithm, static load distribution algorithm and dynamic load adjustment algorithm (SDDA) is proposed, SDDA is designed based on the concept of virtual server, The new algorithm can dynamically adjusts Address-Space and fairness workload for each node after measured it’s capacity. Through research and simulation analysis, compared with the traditional virtual server load balancing algorithm, the SDDA algorithm is with better load balance, faster velocity of load balancing, less load movement cost, and more excellent stability of P2P system.

RelaxDHT

DHT-based P2P systems provide a fault-tolerant and scalable means to store data blocks in a fully distributed way. Unfortunately, recent studies have shown that if connection/disconnection frequency is too high, data blocks may be lost. This is true for most of the current DHT-based systems' implementations. To deal with this problem, it is necessary to build more efficient replication and maintenance mechanisms. In this article, we study the effect of churn on PAST, an existing DHT-based P2P system. We then propose solutions to enhance churn tolerance and evaluate them through discrete event simulation.

An Adaptive and Dynamic Load Balancing Algorithm for Structured P2P Systems

One important issue in the DHT design is how to balance the load across the nodes in the system. To achieve load balance, existing DHT-based P2P systems simply resort to the hash function to map objects to nodes randomly. However, the use of DHT and the heterogeneity of nodes capacities may give rise to load imbalance problems, and affect the DHT system efficiency as well. A new load balance algorithm, static load distribution algorithm and dynamic load adjustment algorithm (SDDA) is proposed, SDDA is designed based on the concept of virtual server, The new algorithm can dynamically adjusts Address-Space and fairness workload for each node after measured it’s capacity. Through research and simulation analysis, compared with the traditional virtual server load balancing algorithm, the SDDA algorithm is with better load balance, faster velocity of load balancing, less load movement cost, and more excellent stability of P2P system.

An Adaptive and Dynamic Load Balancing Algorithm for Structured P2P Systems

One important issue in the DHT design is how to balance the load across the nodes in the system. To achieve load balance, existing DHT-based P2P systems simply resort to the hash function to map objects to nodes randomly. However, the use of DHT and the heterogeneity of nodes capacities may give rise to load imbalance problems, and affect the DHT system efficiency as well. A new load balance algorithm, static load distribution algorithm and dynamic load adjustment algorithm (SDDA) is proposed, SDDA is designed based on the concept of virtual server, The new algorithm can dynamically adjusts Address-Space and fairness workload for each node after measured it’s capacity. Through research and simulation analysis, compared with the traditional virtual server load balancing algorithm, the SDDA algorithm is with better load balance, faster velocity of load balancing, less load movement cost, and more excellent stability of P2P system.

DHT 기반의 P2P 네트워크에서 사용자 행동양식 및 파일 오염에 관한 측정 연구

부패한 파일을 공유하거나, 인덱스 정보에 잘못된 인덱스 레코드를 삽입하는 등의 파일 오염문제는 대다수의 파일 공유 P2P 시스템들의 실질적인 문제가 되어 왔다. 이러한 파일 오염은 사용자들로 하여금 다운받아도 전혀 득이 되지 않는 오염된 파일들을 다운받도록 하거나, 존재하지 않는 파일들에 대한 비생산적인 다운로드 시도를 유도한다. 파일 오염은 네트워크 자원을 낭비할 뿐만 아니라, 사용자들의 활발한 참여를 제한하기 때문에 적절하게 대처하지 못한다면 향후 파일 공유 P2P 시스템 (혹은 비슷한 분산 환경 정보 공유 어플리케이션)의 성공을 기약하기 힘들다. 따라서 효과적인 오염방지 메커니즘의 개발이 시급하다. 본 논문은 대표적인 DHT (distributed hash table) 기반 P2P 시스템인 Kad 네트워크에서 사용자 행동양식 및 파일 오염에 대한 측정 연구를 통해 향후 효과적인 파일 오염방지 메커니즘을 개발하고자 하는 연구자들에게 실질적으로 활용 가능한 정보를 제공한다. File pollution (i.e., sharing of corrupted files, or contaminating index information with bogus index records) is a de facto problem in many file sharing Peer-to-Peer (P2P) systems in use today. Since pollution squanders network resources and frustrates users with unprofitable downloads (due to corrupted files) and unproductive download trials (due to bogus index records), the viability of P2P systems (and similar distributed information-sharing applications) is questionable unless properly addressed. Thus, developing effective anti-pollution mechanisms is an immediate problem in this literature. This paper provides useful information and deep insight with future researchers who want to design an effective anti-pollution mechanism throughout an extensive measurement study of user behavior and file pollution in a representative DHT-based P2P system, the Kad network.

TSS: Efficient Term Set Search in Large Peer-to-Peer Textual Collections

Previous multikeyword search in DHT-based P2P systems often relies on multiple single keyword search operations, suffering from unacceptable traffic cost and poor accuracy. Precomputing term-set-based index can significantly reduce the cost but needs exponentially growing index size. Based on our observations that 1) queries are typically short and 2) users usually have limited interests, we propose a novel index pruning method, called TSS. By solely publishing the most relevant term sets from documents on the peers, TSS provides comparable search performance with a centralized solution, while the index size is reduced from exponential to the scale of O(nlog(n)). We evaluate this design through comprehensive trace-driven simulations using the TREC WT10G data collection and the query log of a major commercial search engine.

LIGHT: A Query-Efficient Yet Low-Maintenance Indexing Scheme over DHTs

DHT is a widely used building block for scalable P2P systems. However, as uniform hashing employed in DHTs destroys data locality, it is not a trivial task to support complex queries (e.g., range queries and k-nearest-neighbor queries) in DHT-based P2P systems. In order to support efficient processing of such complex queries, a popular solution is to build indexes on top of the DHT. Unfortunately, existing over-DHT indexing schemes suffer from either query inefficiency or high maintenance cost. In this paper, we propose LIGhtweight Hash Tree (LIGHT)—a query-efficient yet low-maintenance indexing scheme. LIGHT employs a novel naming mechanism and a tree summarization strategy for graceful distribution of its index structure. We show through analysis that it can support various complex queries with near-optimal performance. Extensive experimental results also demonstrate that, compared with state of the art over-DHT indexing schemes, LIGHT saves 50-75 percent of index maintenance cost and substantially improves query performance in terms of both response time and bandwidth consumption. In addition, LIGHT is designed over generic DHTs and hence can be easily implemented and deployed in any DHT-based P2P system.

Reducing Replication Overhead for Data Durability in DHT Based P2P System

DHT based p2p systems appear to provide scalable storage services with idle resource from many unreliable clients. If a DHT is used in storage intensive applications where data loss must be minimized, quick replication is especially important to replace lost redundancy on other nodes in reaction to failures. To achieve this easily, a simple replication method directly uses a consistent set, such as a leaf set and a successor list. However, this set is tightly coupled to the current state of nodes and the traffic needed to support this replication can be high and bursty under churn. This paper explores efficient replication methods that only glimpse a consistent set to select a new replica. Replicas are loosely coupled to a consistent set and we can eliminate the compulsory replication under churn. Because of a complication of the new replication methods, the careful data management is needed under churn for the correct and efficient data lookup. Results from a simulation study suggest that our methods can reduce network traffic enormously for high data durability.

Efficient, proximity-aware load balancing for DHT-based P2P systems

Many solutions have been proposed to tackle the load balancing issue in DHT-based P2P systems. However, all these solutions either ignore the heterogeneity nature of the system, or reassign loads among nodes without considering proximity relationships, or both. In this paper, we present an efficient, proximity-aware load balancing scheme by using the concept of virtual servers. To the best of our knowledge, this is the first work to use proximity information in load balancing. In particular, our main contributions are: 1) relying on a self-organized, fully distributed k-ary tree structure constructed on top of a DHT, load balance is achieved by aligning those two skews in load distribution and node capacity inherent in P2P systems - that is, have higher capacity nodes carry more loads; 2) proximity information is used to guide virtual server reassignments such that virtual servers are reassigned and transferred between physically close heavily loaded nodes and lightly loaded nodes, thereby minimizing the load movement cost and allowing load balancing to perform efficiently; and 3) our simulations show that our proximity-aware load balancing scheme reduces the load movement cost by 11-65 percent for all the combinations of two representative network topologies, two node capacity profiles, and two load distributions of virtual servers. Moreover, we achieve virtual server reassignments in O(log N) time.