applications. In addition to labor saving, the ben-efits delivered by these advances are many and include reliable prediction of outcome, minimization of downtime, system-produced documentation, and support for archiving, historical queries, and provenance. The PRISM/PRISM++ system delivers these benefits

within the last w time units. We show that our protocols are optimal, not just in terms of the communication used, but also that they use minimal or near minimal (up to logarithmic factors) time to process each new item, and space to operate. Categories and Subject Descriptors F.2.2 [Analysis

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digests or fingerprints for attack signatures during its programming phase. In its querying phase, the framework quickly identifies attack-free connections by transforming input traffic into its fingerprint space and matching its digest against those of attack signatures. If the legitimacy of a stream

Massively multiplayer online games (MMOGs) have become increasingly popular in the recent years, particularly in the form of online role-playing games (MMORPGs). These games support up to several ten thousand players interacting in a virtual game world. The current commercially successful games are client-server based, which is feasible for relatively slow role-playing games. Those have modest bandwidth and latency requirements and are paid for by their customers. For MMOGs with higher realtime requirements and/or a smaller number of customers willing to pay, peer-to-peer networking seems to be a serious alternative. This work analyzes the implementation of both a client-server and a peer-to-peer networking model for the prototype shooter game Planet π4. Initially, a survey introduces recent academic approaches to peer-to-peer systems specifically designed for games. Of those, one system is selected for implementation with Planet π4. Planet π4 is improved in several aspects for the purpose of analyzing various network implementations. First, its architecture is restructured and cleaned to allow for an easy replacement of the networking component. Second, its core is modified to work in a completely event-based mode, supporting the execution of the game in an discrete-event-based network simulator. Third, a simple artificial intelligence player is developed for workload generation in large (and possibly simulated) networks. Furthermore, the newly developed transport protocol CUSP is applied for the network implementation, thus the game is the first real application using CUSP. Finally the game Planet π4 is integrated with the CUSP network simulator, allowing to run the whole game in a simulated network without the need for modification of its core components. Kurzfassung Massen-Mehrspieler-Onlinespiele (Massively multiplayer online games; MMOGs) wurden in den vergangenen Jahren zunehmend populär, insbesondere in Form von Online-Rollenspielen (MMORPGs). In

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Messaging is a basic service in sensornets. Yet the unique system and application prop-erties of sensornets pose substantial challenges for the messaging design: Firstly, dynamic wireless links, constrained resources, and application diversity challenge the architecture and protocol design of sensornet messaging; Secondly, complex faults and large system scale introduce new challenges to the design of fault-tolerant protocols. The objective of this dissertation is to address the aforementioned challenges of sensornet messaging. Despite the extensive effort in studying sensornet messaging, the lack of a basic un-derstanding of its essential components has been an obstacle for reliable, efcient, and reusable messaging services in sensornets. To address this problem, one task of this dis-sertation is to identify the basic components of sensornet messaging and to study the re-lated algorithmic design issues. More specically, we propose the messaging architecture SMA that consists of three components: trafc-adaptive link estimation and routing (TLR), application-adaptive structuring (AST), and application-adaptive scheduling (ASC). TLR deals with dynamic wireless links as well as the impact of application trafc patterns on

Hiermit versichere ich, die vorliegende Master-Thesis ohne Hilfe Dritter nur mit den angegebenen Quellen und Hilfsmitteln angefertigt zu haben. Alle Stellen, die aus Quellen entnommen wurden, sind als solche kenntlich gemacht. Diese Arbeit hat in gleicher oder ähnlicher Form noch keiner Prüfungsbehörde vorgelegen. Darmstadt, den 17. Mai 2011 (Marcel Lucas) The popularity of Networked Virtual Environments (NVE) increased remarkably in recent years where a plethora of players participate concurrently. Traditional approaches applying the Client/Server pattern swiftly reach their limit in terms of scalability and maintainability. Hence, different approaches are based on Peer-to-Peer (P2P) technology. In particular, fast-paced NVEs stress these systems and most likely cause high overlay maintenance overhead. This Master’s Thesis presents a novel approach to spatial Publish/Subscribe (Pub/Sub) in P2P NVEs. The unstructured P2P system BubbleStorm offers flexible and scalable means and is therefore used as a fundamental base for the developed Pub/Sub system. As the evaluation of the subscription is performed

ACKNOWLEDGMENTS I would like to give many thanks to Dr. Shengli Fu and Dr. Yan Huang as my advi-

Abstract—We investigate achievable degrees of freedom (DoF) for a multiple-input multiple-output (MIMO) multiway relay channel (mRC) with L clusters andK users per cluster. Each user is equipped with M antennas and the relay with N antennas. We assume a new data exchange model, termed clustered full data exchange, i.e., each user in a cluster wants to learn the messages of all the other users in the same cluster. Novel signal alignment techniques are developed to systematically construct the beamforming matrices at the users and the relay for efficient physical-layer network coding. Based on that, we derive an achievable DoF of the MIMO mRC with an arbitrary network configuration of L and K, as well as with an arbitrary antenna configuration of M and N. We show that our proposed scheme achieves the DoF capacity when M N