A Self-Stabilizing Locality-Aware Peer-to-Peer Network Combining Random Networks, Search Trees, and DHTs (original) (raw)
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3 nuts : A Locality-Aware Peer-to-Peer Network Combining Random Networks , Search Trees , and DHTs
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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...
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ABSTRACT In this poster we will present our work on the design of efficient and reliable unstructured peer-to-peer (P2P) systems. Our work focuses on creating well-connected unstructured P2P overlay that can perform efficient searching and message routing. We show that well designed systems can tolerate high node failures (> 25%) while maintaining connectivity and still resolving searches with few messages.
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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.
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Distributed hash tables (DHTs), used in a number of structured peer-to-peer systems provide efficient mechanisms for resource location. A key distinguishing feature of current DHT systems like Chord [15], Pastry [12], and Tapestry [19] is the way they handle locality in the underlying network. Topology-based node identifier assignment, proximity routing, and proximity neighbor selection are examples of heuristics used to minimize message delays in the underlying network. While these heuristics are sometimes effective, they all rely on a single global overlay that may install the key of a popular object at a node far from most of the nodes accessing it. Furthermore, a response to a lookup message does not contain any locality information about the nodes holding a copy of the object. We address these issues by defining Plethora, a novel two-level overlay peer-to-peer network. A local overlay in Plethora acts as a locality-aware cache for the global overlay, grouping nodes close together in the underlying network. Local overlays are constructed by exploiting the structure of the Internet as Autonomous Systems. We present a detailed experimental study that demonstrates the practicality of the system, and shows performance gains in response time of upto 60% compared to a single global overlay. We also present efficient distributed algorithms for maintaining local overlays in the presence of node arrivals and departures.
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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.
SOLD: Self-Organizing Lookups in DHTs for better Performance over Unstable P2P Overlay Links
The quality of service (QoS) of a distributed hash table (DHT) lookup is gaining importance with the growing number of services adopting the P2P paradigm. Examples of applications that could largely benefit from an improved timeliness and reliability of message exchange in DHTs are Domain Name System (DNS), or even newer types of distributed location-based services in a mobile environment. The bursty effects of Internet traffic on latency, congestion, and loss can change the short term state of the overlay links in the DHT. The quick changes to overlay link/node states cannot be taken into account while structuring long term P2P routes. This paper proposes self-organizing mechanisms to improve the QoS for DHT lookups, without changing the structure of the DHT network. Different kinds of lookup replication techniques are implemented on top of the DHT to restrict the influence of the heterogeneous capabilities of the overlay routes while offering self-adaptive and robust high performance lookups.
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Skip Tree Graph is a novel, distributed, data structure for peer-to-peer systems that supports exact-match and order-based queries such as range queries efficiently. It is based on skip trees, which are randomised balanced search trees equivalent to skip lists and designed to provide improved concurrency. Skip tree graphs constitute an extension of skip graphs enhancing their performance in both, exact-match and range queries. Moreover, skip tree graph maintains the underlying balanced tree structures using randomization and local operations, which provides a greater degree of concurrency and scalability.
OBST: A self-adjusting peer-to-peer overlay based on multiple BSTs
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The design of scalable and robust overlay topologies has been a main research subject since the very origins of peerto-peer (p2p) computing. Today, the corresponding optimization tradeoffs are fairly well-understood, at least in the static case and from a worst-case perspective.
Locality in structured peer-to-peer networks
Journal of Parallel and Distributed Computing, 2006
Distributed hash tables (DHTs), used in a number of structured peer-to-peer (P2P) systems, provide efficient mechanisms for resource placement and location. A key distinguishing feature of current DHT systems, such as Chord, Pastry, CAN and Tapestry, is the way they handle locality in the underlying network. Topology-based node identifier assignment, proximity routing, and proximity neighbor selection are examples of heuristics used to minimize message delays in the underlying network. While these heuristics are sometimes effective, they all rely on a single global overlay that may install the key of a popular object at a node far from most of the nodes accessing it. Furthermore, a response to a lookup message does not contain any locality information about the nodes holding a copy of the object. We address these issues in Plethora, a novel two-level overlay P2P network. A local overlay in Plethora acts as a locality-aware cache for the global overlay, grouping nodes close together in the underlying network. Local overlays are constructed by exploiting the organization of the Internet into autonomous systems (ASs). We present a detailed experimental study that demonstrates performance gains in response time of up to 60% compared to a single global Pastry overlay. We also present efficient distributed algorithms for maintaining local overlays in the presence of node arrivals and departures.
Jelly: a dynamic hierarchical P2P overlay network with load balance and locality
24th International Conference on Distributed Computing Systems Workshops, 2004. Proceedings., 2004
P2P systems based on Distributed hash table (DHT) such as CAN, Chord, Pastry, and Tapestry, use uniform hash functions to ensure load balance in each participant nodes. But the evenly distributed behavior in the virtual space destroys the locality between participant nodes. The topology-based hierarchical overlay network like Grapes, exploits the physical distance information among the nodes to construct a two-layered hierarchy, highly improves the locality, but damages the load balance property in original DHTs. In this paper, we propose a dynamic P2P overlay infrastructure, called Jelly. It can achieve both the load balancing and locality properties. Its design is based on the hierarchical overlay and uses the DHT as its routing algorithm. Because the load balancing issue in a hierarchical overlay is originated from whether the virtual hierarchy is balanced or not, Jelly uses a node joining mechanism as a fine-tuning tool and a dynamic checking mechanism as a coarse-tuning tool to balance the hierarchy. We also find that the average routing hops is a practical metric to evaluate the network size, and it is useful for Jelly's dynamic mechanism.