Gemeinsamer Workshop von Universitaetsrechenzentrum und Professur Rechnernetze und verteilte Systeme der Fakultaet fuer Informatik der TU Chemnitz. RAAS ist ein Konzept um gleichlautende Aufgaben für und über mehrere Remote-Computer auszuführen. Das Konzept wird dargestellt und anhand von Beispielen erläutert. Das Admin-Tool wird im Anschluss mit Praxisaufgaben vorgestellt.

Gemeinsamer Workshop von Universitaetsrechenzentrum und Professur Rechnernetze und verteilte Systeme der Fakultaet fuer Informatik der TU Chemnitz. Grenzen zentralisierter Ansätze, Charakteristika und Anwendungsgebiete für Peer-to-Peer, Probleme und Herausforderungen

Diese Arbeit beschreibt ein Konzept für eine verteilte Datensicherung unter Nutzung freier Ressourcen von Arbeitsplatzrechnern. Das vorzustellende System beinhaltet entsprechende Maßnahmen, um sowohl die Authentizität und Vertraulichkeit der zu sichernden Daten zu gewährleisten, als auch eine möglichst hohe Wahrscheinlichkeit für die Wiederherstellung zu erreichen.

Thesis (M.S.)--Youngstown State University, 2009. / Includes bibliographical references (leaf 42). Also available via the World Wide Web in PDF format.

Thesis (Ph. D.)--University of Chicago, Dept. of Computer Science, December 2003. / Includes bibliographical references. Also available on the Internet.

Zugl.: Bremen, Univ., Diss., 2009

Includes bibliographical references (p. 74-77).

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Peer-to-peer (P2P) video streaming has become a very popular and cost-effective solution to provide video-on-demand (VoD) streaming service to a large group of Internet users. Recent advances of layered video coding are shown to be promising in addressing the problem of receiver heterogeneity in P2P streaming networks. The key idea is to encode a raw video into multiple non-overlapped layers. Peers in the network can enjoy different streaming qualities by subscribing to different number of layers according to their specific network bandwidth. In this thesis, a systematic and comprehensive study of layered P2P VoD streaming networks is conducted. We first investigate the overlay construction problem that concerns the strategy of forming a logical overlay network for peers to exchange data pieces. We propose a neighbor relationship management algorithm to maintain a stable yet diversified neighbor set to facilitate adding or dropping a video layer, i.e. layer adaptation. Subsequently, an incentive scheme is designed to differentiate neighbors’ contributions at different layers, and a peer is allowed to adjust its number of neighbors according to its average service response time. We then develop an efficient layer adaptation algorithm for adjusting the number of video layers a peer subscribes to. We use a sliding buffer window for video piece scheduling, and make use of the time difference between the playback point and the starting point of the sliding window to initiate the process of adding or dropping a layer. A probing period is also introduced to ensure the adding decision is indeed correct. We next focus on designing piece scheduling algorithm for video data exchange among peers. At each peer, a utility function for calculating the relative importance of each missing video data piece is designed. In piece scheduling, a peer prefers a piece with higher utility value. We show that our utility based piece scheduling algorithm yields better video quality than conventional approaches. Last but not least, we study the request peer selection problem for identifying the most suitable neighbor for a peer to make a piece request. Two algorithms are designed, smallest service response time first (SSF) and closest playback point first (CPF). SSF ensures peers with larger uplink bandwidths to serve more requests, and CPF encourages a newly joined peer to contribute its uplink bandwidth as quickly as possible. We show that there exists a sweet spot by properly combining the two together. Although our algorithms are presented sequentially in addressing each of the problems above, they do interact with each other. Throughout our study, a comprehensive packet-level simulator is used to closely examine and analyze such interactions. With that, our algorithms are judicially designed and fine-tuned for best performance. To the best of our knowledge, our in-house developed simulator is the most comprehensive packet-level simulator for layered P2P VoD streaming. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Peer-to-Peer (P2P) technology has been developed rapidly during the past few years. Due to its superiorities on robustness and scalability, P2P technology has been viewed as a promising networking technology and many studies have been done on how to improve P2P technology. P2P file distribution, as a major application of P2P technology, has also been studied a lot. The amount of time required for all peers to get the file has been considered as a major optimization metric, which we refer as the file distribution time. Researchers have proposed protocols to minimize the file distribution time for different cases. However, most of the existing works are based on the single-file scenario. On the other hand, studies show that in a file sharing application, users may download multiple files at the same time. In this thesis, we analyze the file distribution time for the distribution of multiple files in both wired and wireless networks. We develop explicit expressions for lower bound of time needed to distribute multiple files in a heterogeneous P2P fluid model. Unlike the single-file scenario, we demonstrate that the theoretical lower bound in multi-file scenario is not always achievable. With a comprehensive consideration of all the configurations, we develop algorithms to partition the bandwidth of all the peers for a particular file such that the file distribution time is optimal. / published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy