SLoPCloud: An Efficient Solution for Locality Problem in Peer-to-Peer Cloud Systems

Peer-to-Peer (P2P) cloud systems are becoming more popular due to the high computational capability, scalability, reliability, and efficient data sharing. However, sending and receiving a massive amount of data causes huge network traffic leading to significant communication delays. In P2P systems, a considerable amount of the mentioned traffic and delay is owing to the mismatch between the physical layer and the overlay layer, which is referred to as locality problem. To achieve higher performance and consequently resilience to failures, each peer has to make connections to geographically closer peers. To the best of our knowledge, locality problem is not considered in any well known P2P cloud system. However, considering this problem could enhance the overall network performance by shortening the response time and decreasing the overall network traffic. In this paper, we propose a novel, efficient, and general solution for locality problem in P2P cloud systems considering the round-trip-time (RTT). Furthermore, we suggest a flexible topology as the overlay graph to address the locality problem more effectively. Comprehensive simulation experiments are conducted to demonstrate the applicability of the proposed algorithm in most of the well-known P2P overlay networks while not introducing any serious overhead.

Overlay Algorithm for Simple Subdivision of Arbitrary Polygon in Plane

The overlay algorithm is an important branch in computational geometry field, it is an important process for computing exact Minkowski sum of two convex polyhedrons. By improving the existing plane sweep algorithm, the overlay algorithm for simple subdivision of arbitrary polygon in plane is given. The algorithm can be used to overlay arbitrary polygon after subdivision into simple polygon in the plane. It has lower time complexity than the existing overlay algorithm. The whole algorithm consists of three steps: line segment intersection, reconstructing topology and constructing the DCEL for overlay graph. The results show that the algorithm can compute the overlay of two planar subdivisions in linear time.

Hierarchical Structured Peer-to-Peer Networks

Structured peer-to-peer networks are scalable overlay network infrastructures that support Internet-scale network applications. A globally consistent peer-to-peer protocol maintains the structural properties of the network with peers dynamically joining, leaving and failing in the network. In this chapter, the authors discuss hierarchical distributed hash tables (DHT) as an approach to reduce the overhead of maintaining the overlay network. In a two-level hierarchical DHT, the top-level overlay consists of groups of nodes where each group is distinguished by a unique group identifier. In each group, one or more nodes are designated as supernodes and act as gateways to nodes at the second level. Collisions of groups occur when concurrent node joins result in the creation of multiple groups with the same group identifier. This has the adverse effects of increasing the lookup path length due to a larger top-level overlay, and the overhead of overlay network maintenance. We discuss two main approaches to address the group collision problem: collision detection-and-resolution, and collision avoidance. As an example, they describe an implementation of hierarchical DHT by extending Chord as the underlying overlay graph.