Analysis of peer-to-peer file dissemination

In recent years, overlay networks have proven a popular way of disseminating potentially large files from a single server S to a potentially large group of N end users via the Internet. A number of algorithms and protocols have been suggested, implemented and studied. In particular, much attention has been given to peer-to-peer (P2P) systems such as BitTorrent, Slurpie, SplitStream, Bullet and Avalanche. The key idea is that the file is divided into M parts of equal size and that a given user may download any one of these -- or, for Avalanche, linear combinations of these -- either from the server or from a peer who has previously downloaded it. However, performance analysis of P2P systems for file dissemination has typically been limited to comparing one system relative to another and typically been realized by means of simulations and measurements. We give the minimal time to fully disseminate the file of M parts from a server to N end users in a centralized scenario. In the scheduling literature this completion time is referred to as makespan. We thereby provide a lower bound which can be used as a performance benchmark for any P2P file dissemination system. We also investigate the part of the loss in efficiency that is due to the lack of centralized control in practice. Using simulation as well as direct computation, we show that even a simple and natural randomized strategy disseminates the file in an expected time that grows with N in a similar manner to the minimal time achieved with a centralized controller. This suggests that the performance of necessarily decentralized P2P file dissemination systems should still be close to our performance bound

Improving file distribution performance by grouping in peer-to-peer networks

It has been shown that the peer-to-peer paradigm is more efficient than the traditional client-server model for file sharing among a large number of users. Given a group of leechers who wants to download a single file and a group of seeds who possesses the whole file, the minimum time needed for distributing the file to all users can be calculated based on their bandwidth availabilities. A scheduling algorithm has been developed so that every leecher can obtain the file within this minimum time. Unfortunately, this mechanism is not optimal with regard to the average download time among the peers. In this paper, we study how to reduce the average download time without prolonging the time needed for all leechers to obtain the file from a theoretical perspective. Based on the bandwidth capacities, the seeds and leechers are divided into different groups. We identify the necessary conditions for grouping to bring about benefits. We also study the impact on performance when leechers leave the system before the downloading process is complete. To evaluate our mechanism, we conduct extensive simulations and compare the performance with a BitTorrentlike file sharing algorithm. The results show that our grouping protocol successfully reduces the average download time over a wide range of system configurations. © 2009 IEEE.published_or_final_versio

Design and evaluation of load balancing algorithms in P2P streaming.

Wang, Yongzhi.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.Includes bibliographical references (p.68-72).Abstract also in Chinese.Abstract --- p.iAcknowledgement --- p.iiChapter 1 --- Introduction --- p.1Chapter 2 --- Abstract Model --- p.7Chapter 2.1 --- Request allocation problem --- p.7Chapter 2.2 --- Neighbor selection problem --- p.11Chapter 3 --- Simulation Model --- p.14Chapter 4 --- Load Balancing Algorithms --- p.18Chapter 4.1 --- Request allocation --- p.18Chapter 4.2 --- Neighbor selection algorithms --- p.24Chapter 4.2.1 --- What to measure? --- p.24Chapter 4.2.2 --- Timeout-based neighbor selection algorithms --- p.25Chapter 4.2.3 --- Periodic neighbor selection algorithms --- p.33Chapter 4.2.4 --- Comparison: Timeout-based versus Periodical neighbor selection algorithms --- p.39Chapter 4.3 --- Further experiments --- p.41Chapter 4.3.1 --- Request window size --- p.41Chapter 4.3.2 --- Impact of K --- p.42Chapter 4.3.3 --- Adaptive adjustment of the neighbor selection period --- p.43Chapter 4.3.4 --- Performance with adequate bandwidth --- p.45Chapter 5 --- Minimizing Server´ةs Load --- p.49Chapter 6 --- Background Study --- p.56Chapter 6.1 --- P2P content distribution system --- p.56Chapter 6.1.1 --- P2P File sharing system --- p.56Chapter 6.1.2 --- P2P streaming system --- p.59Chapter 6.1.3 --- P2P Video on Demand system --- p.61Chapter 6.2 --- Congestion control --- p.62Chapter 7 --- Conclusion --- p.67Bibliography --- p.6

Performance and availability analysis of BitTorrent-like file sharing systems.

Fan Bin.Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.Includes bibliographical references (leaves 72-76).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Background --- p.1Chapter 1.2 --- Motivation --- p.3Chapter 1.3 --- Our Contribution --- p.5Chapter 1.4 --- Structure of the thesis --- p.7Chapter 2 --- Related Work --- p.8Chapter 2.1 --- Measurement Based Studies --- p.8Chapter 2.2 --- Analytical Modeling of Bit Torrent System --- p.9Chapter 2.3 --- Fairness and Incentive Mechanism --- p.11Chapter 3 --- Scalability --- p.12Chapter 3.1 --- Analytical Model --- p.12Chapter 3.2 --- Steady-State Performance Measures --- p.18Chapter 3.3 --- Model Validation and Evaluation --- p.22Chapter 3.4 --- Model Extension For Peers behind Firewalls --- p.28Chapter 3.5 --- Summary --- p.32Chapter 4 --- File Availability --- p.33Chapter 4.1 --- Modeling the File Availability --- p.34Chapter 4.2 --- Performance of Different Chunk Selection Algorithms --- p.38Chapter 4.3 --- Summary --- p.42Chapter 5 --- Fairness --- p.44Chapter 5.1 --- Mathematical Model --- p.45Chapter 5.1.1 --- The Generic Model of Uplink Sharing --- p.45Chapter 5.1.2 --- A Dynamic Model of Multiple Classes of Peers --- p.46Chapter 5.1.3 --- Performance Metric --- p.47Chapter 5.1.4 --- Fairness Metric --- p.49Chapter 5.2 --- Rate Assignment Strategies --- p.51Chapter 5.2.1 --- Uploading Rate --- p.51Chapter 5.2.2 --- Rate Assignment for Optimal Downloading Time --- p.51Chapter 5.2.3 --- Rate Assignment for Optimal Fairness --- p.53Chapter 5.2.4 --- Rate Assignment for Max-min Allocation --- p.54Chapter 5.2.5 --- Performance and Fairness Comparison --- p.56Chapter 5.3 --- A Family of Distributed Algorithms --- p.58Chapter 5.3.1 --- Selective Uploading --- p.60Chapter 5.3.2 --- Non-discriminative Uploading --- p.62Chapter 5.3.3 --- Design Knobs --- p.63Chapter 5.4 --- Performance Evaluation --- p.63Chapter 5.5 --- Summary --- p.69Chapter 6 --- Conclusion --- p.70Bibliography --- p.72Chapter A --- Proof of Theorem 3.1 --- p.77Chapter B --- Proof of Theorem 5.2 --- p.8

Collaborative Data Access and Sharing in Mobile Distributed Systems

The multifaceted utilization of mobile computing devices, including smart phones, PDAs, tablet computers with increasing functionalities and the advances in wireless technologies, has fueled the utilization of collaborative computing (peer-to-peer) technique in mobile environment. Mobile collaborative computing, known as mobile peer-to-peer (MP2P), can provide an economic way of data access among users of diversified applications in our daily life (exchanging traffic condition in a busy high way, sharing price-sensitive financial information, getting the most-recent news), in national security (exchanging information and collaborating to uproot a terror network, communicating in a hostile battle field) and in natural catastrophe (seamless rescue operation in a collapsed and disaster torn area). Nonetheless, data/content dissemination among the mobile devices is the fundamental building block for all the applications in this paradigm. The objective of this research is to propose a data dissemination scheme for mobile distributed systems using an MP2P technique, which maximizes the number of required objects distributed among users and minimizes to object acquisition time. In specific, we introduce a new paradigm of information dissemination in MP2P networks. To accommodate mobility and bandwidth constraints, objects are segmented into smaller pieces for efficient information exchange. Since it is difficult for a node to know the content of every other node in the network, we propose a novel Spatial-Popularity based Information Diffusion (SPID) scheme that determines urgency of contents based on the spatial demand of mobile users and disseminates content accordingly. The segmentation policy and the dissemination scheme can reduce content acquisition time for each node. Further, to facilitate efficient scheduling of information transmission from every node in the wireless mobile networks, we modify and apply the distributed maximal independent set (MIS) algorithm. We also consider neighbor overlap for closely located mobile stations to reduce duplicate transmission to common neighbors. Different parameters in the system such as node density, scheduling among neighboring nodes, mobility pattern, and node speed have a tremendous impact on data diffusion in an MP2P environment. We have developed analytical models for our proposed scheme for object diffusion time/delay in a wireless mobile network to apprehend the interrelationship among these different parameters. In specific, we present the analytical model of object propagation in mobile networks as a function of node densities, radio range, and node speed. In the analysis, we calculate the probabilities of transmitting a single object from one node to multiple nodes using the epidemic model of spread of disease. We also incorporate the impact of node mobility, radio range, and node density in the networks into the analysis. Utilizing these transition probabilities, we construct an analytical model based on the Markov process to estimate the expected delay for diffusing an object to the entire network both for single object and multiple object scenarios. We then calculate the transmission probabilities of multiple objects among the nodes in wireless mobile networks considering network dynamics. Through extensive simulations, we demonstrate that the proposed scheme is efficient for data diffusion in mobile networks