Scalable Data Access in Peer-to-Peer Systems Using Unbalanced Search Trees

With the appearance of Peer-to-Peer information systems the interest in scalable and decentralized data access structures is attracting increasingly interest. We propose to that end P-Grid, a scalable data access structure resulting from the distribution of a binary prefix tree. When adapting the P-Grid structure to skewed data distributions one obtains unbalanced search trees. The key result of this paper shows that unbalanced trees do not harm as long as communication is considered as the critical cost and the access structures are constructed properly. Besides proving this result we propose the necessary distributed, randomized algorithms that allow to construct the P-Grid in a self-organized manner such that the tree structure dynamically adapts to the data distribution and the aforementioned result is applicable

A Scalable Name Resolution System for Information Centric Networking

Information Centric Networking (ICN) is a new paradigm, aimed at shifting to the future Internet from host centric to a content centric approach. ICN focuses on retrieval and dissemination of information between pairwise communications of hosts. Information are organized in the form of Information Objects (IO), known as Named Data Objects (NDO). These NDO are location independent. Objects in ICN are stored in the system overlay; popularly known as Name Resolution System (NRS). NDOs are requested by the Subscribers in the network to get the needed information from the Publishers, through NRS. Thus, the NRS is responsible in forwarding the interest packets based on the names of NDOs. This application of ICN depends on the scalability of the NRS. To design NRS, the most significant issue is scalability due to the ever-increasing number of NDOs. This paper aims to present the issues, by proposing balanced binary tree data structure to organize and store the NDOs. The methodology proposed in this work is thus; for every new insertion in the tree, a Balance Factor (BF) is computed to balance the height of left and right sub-tree. According to our investigation, balanced binary tree provides less searching time when compared to the Distributed Hash Table (DHT) approach. Simulation results show that End-to-End delay decreases by increasing the throughput in the network

Search optimizations in structured peer-to-peer systems

DHT systems are structured overlay networks capable of using P2P resources as a scalable platform for very large data storage applications. However, their efficiency expects a level of uniformity in the association of data to index keys that is often not present in inverted indexes. Index data tends to follow non-uniform distributions, often power law distributions, creating intense local storage hotspots and network bottlenecks on specific hosts. Current techniques like caching cannot, alone, cope with this issue. We propose a distributed data structure based on a decentralized balanced tree to balance storage data and network load more uniformly across hosts. The results show that the data structure is capable of balancing resources, in particular when performing multiple keyword searches

Broadcasting in Prefix Space: P2P Data Dissemination with Predictable Performance

A broadcast mode may augment peer-to-peer overlay networks with an efficient, scalable data replication function, but may also give rise to a virtual link layer in VPN-type solutions. We introduce a simple broadcasting mechanism that operates in the prefix space of distributed hash tables without signaling. This paper concentrates on the performance analysis of the prefix flooding scheme. Starting from simple models of recursive $k$-ary trees, we analytically derive distributions of hop counts and the replication load. Extensive simulation results are presented further on, based on an implementation within the OverSim framework. Comparisons are drawn to Scribe, taken as a general reference model for group communication according to the shared, rendezvous-point-centered distribution paradigm. The prefix flooding scheme thereby confirmed its widely predictable performance and consistently outperformed Scribe in all metrics. Reverse path selection in overlays is identified as a major cause of performance degradation.Comment: final version for ICIW'0

Efficient Search in Unbalanced, Randomized Peer-To-Peer Search Trees

Scalable mechanisms to support efficient key-based search in distributed systems are an important part of the infrastructure of peer-to-peer systems and global information systems. They received substantial attention both in information and communication systems research. A particularly important class of approaches is based on a principle of scalable distribution of binary search trees that has been introduced by Plaxton \cite{PLAXTON}. When adapting the shape of such a tree search structure to the data distribution in order to obtain load balancing, the search trees may become highly unbalanced. We show that for P-Grid, a Plaxton-like distributed search structure that we first introduced in \cite{PGRID1}, the expected communication cost for searches is strictly limited by $\log(n)$ where $n$ is the number of peers. This result is completely independent of the shape of the underlying tree. The approach exploits the randomization principle of the P-Grid structure by virtue of its decentralized and randomized construction process