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UBC Theses and Dissertations

Simulation and topology generation for large-scale distributed systems Cheng, Lechang


Simulation of P2P systems at large scale is important because some problems with the protocols or their implementations might not appear at smaller scales. In this work, a parallel message-level simulator, P2PNet, is proposed, which can simulate P2P systems with up to tens of thousands of nodes. P2PNet applies the technique of time expansion and uses real time to synchronize the processing of events among the participating processors. Simulation results show that P2PNet has small overhead compared with a single-processor event-driven simulator, a large speedup when multiple computers are used and no late events. One of the other challenges of large-scale network simulations is the lack of scalable and realistic Internet topology generators. In this work, we propose a topology generator which can generate accurate large-scale models of the Internet. We extract the AS (autonomous system) level and router level topology of the Internet with Internet measurement data. A compact routing core is built with the AS topology and router cluster topology. Each generated topology consists of the routing core and a set of end nodes connected to router clusters. The generated topology is realistic since its routing core is extracted from Internet. We also propose efficient algorithms to compute AS level path. The current routing algorithms of DHT-based P2P systems have a large end-to-end delay and inconsistent routing performance because of their random selection of identifiers (IDs). In this paper, an Internet topology based overlay construction method is proposed for tree-based DHTs. The node ID is divided into three parts and assigned according to the autonomous system (AS), IP network prefix, and IP address of the node. This algorithm assigns the AS ID prefix based on the AS-level Internet topology. The assignment of AS ID prefixes also takes into account the node densities of ASes to alleviate the ID space load imbalance. Simulation results show that this method can reduce the routing stretch and the standard deviation of the routing stretch without introducing any single points of failure.

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