List of relevant chapters

Mobile Systems

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  Load measurement at different interfaces of a protocol / service hierarchy within service-integrated networks focussing on video traffic (MPEG-1/ -2, H.261, H. 263) on one hand and on UDP / IP traffic on the other hand
  
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  Load modelling based on measurements covering again video traffic as well as packet traffic
  
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  Load prediction by means of maudlin load transformation processes
  
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  Construction of load generators for synthetic load in LANs or in Internets;
  
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  Traffic management, e.g. priorization of video traffic in DiffServ based networks
  

Distributed Multimedia Platforms

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  Wolf J., Wolfinger B.E., Efficient Resource Management for Distributed Applications with Real-Time Requirements in Broadcast Networks, 8th CaberNet Radicals Workshop, 2003
  
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  Wolfinger B.E., Wolf J., le Grand G., Improving Node Behavior in a QoS Control Environment for Local Broadcast Networks, Proc. of the International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS), 2003
  
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  Wolf J., Wolfinger B.E., le Grand G., Anelli P., Leistungsbewertung von Algorithmen zur dynamischen Ressourcenverwaltung in lokalen "Broadcast"- Netzen, GI/ITG-Fachtagung "Kommunikation in Verteilten Systemen" KiVS 2003, Leipzig, Februar 2003
  

Distributed Systems Security, Software Architectures for Distributed and Dependable Systems

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  P. Herrmann: Formal Security Policy Verification of Distributed Component-Structured Software. To appear in: 23rd IFIP International Conference on Formal Techniques for Networked and Distributed Systems (FORTE'2003), IFIP, LNCS, Berlin, September/October 2003, Springer-Verlag.
  
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  P. Herrmann: Trust-Based Protection of Software Component Users and Designers. In: 1st International Conference on Trust Management, pp. 75-90, LNCS 2692, Heraklion, May 2003, Springer-Verlag.
  
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  P. Herrmann, L. Wiebusch, H. Krumm: State-Based Security Policy Enforcement in Component-Based E-Commerce Applications. In: 2nd IFIP Conference on E-Commerce, E-Business & E-Government (I3E), pp. 195-209, Lisbon, October 2002. Kluwer Academic Publisher.
  

As in the case of other non-trivial software-based systems, we must assume that failure of safety critical systems is possible, and attempt to discover whether or not, in the case of each system, failure is sufficiently unlikely for the system to be licensed for operational use. There are a number of special features of complex, software-based, safety-critical systems which contribute to the difficulty of assessing their dependability. There is insufficient objective statistical evidence to assure - by testing, or from actual operation of related systems in related environments - that the required level of reliability has been achieved in the case of a new system. For this reason, safety assessors turn to other sources of evidence in an attempt to increase their assurance that such a system is fit for purpose. These other sources might include measurable evidence relating to the quality of the requirements elicitation and design processes, or to the competence of development personnel; as well as the use of more subjective expert assessment of these and other factors. In taking account of much of this evidence, there will not always be scientifically accepted or widely agreed relationships and causal models on which to rely.

This project attempts to investigate the contribution that graphical probability models or "belief networks" might make to these problems. In particular it focuses on: Examining and comparing the value of alternative graphical formalisms such as Directed Acyclic Graphs, Undirected Graphs and Chain Graphs. In particular we hope that use of these multiple formalisms might increase our assurance that the builders and users of such graphical models understand the "system of conditional independence assumptions" depicted by such graphs as fully and correctly as possible. The development of automated methods of providing a multiplicity of forms of feedback of the structure, assumptions and consequences of such graphical probability models. We intend that this model feedback should include automatically computed symbolic (as well as numeric) forms of model output. In these ways we aim to develop methods of deepening a safety assessment expert's appreciation of, and interaction with, the formal conditional-independence model expressed by a graphical formalism, and hence gaining confidence that such models, ultimately and after appropriate adjustment, can become a valuable aid to and a fair representation of the coherent beliefs of such experts.

List of relevant chapters:

Dependable Systems

Distributed Systems Security, Rigorous Design

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  M. Kwiatkowska, G. Norman and J. Sproston Probabilistic Model Checking of Deadline Properties in the IEEE1394 FireWire Root Contention Protocol Special Issue of Formal Aspects of Computing, 14, pp. 295-318 2003
  
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  M. Kwiatkowska, G. Norman, R. Segala, J. Sproston Automatic Verification of Real-time Systems with Discrete Probability Distributions Theoretical Computer Science, 282, pp. 101-150 2002
  
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  Verifying Quantitative Properties of Continuous Probabilistic Timed Automata (M.Z. Kwiatkowska, R. Segala. J. Sproston). In Proc. 12th International Conference on Concurrency Theory (CONCUR'00), LNCS 1877, pp. 123-137, Springer-Verlag 2000
  

In this project we exploit knowledge about recent requests at web-proxies, obtained from a statistical study of request logs, to improve the performance (response time and hit rate) of web proxy servers. We do so by obtaining, using statistical techniques, a classification of the proxy requests based on the requested object size. This classification then forms the basis for a class-based caching approach and a weighted-fair priority queueing approach. Analytical studies, simulations and a prototype implementation show the advantages of our approach, which can be implemented in a very effective way (with lower costs than competing caching and scheduling strategies). Our approach also allows for an adaptive scheduling and caching scheme (with which we are currently experimenting).

Service-oriented Computing

This project aims to build a public infrastructure for wide-area distributed computing. We envisage a world in which Xenoserver execution platforms will be scattered across the globe and available for any member of the public to submit code for execution. Crucially, the sponsor of the code will be billed for all the resources used or reserved during the course of execution. This will serve to encourage load balancing, limit congestion, and hopefully even make the platform self-financing. As part of this project we are developing XenoStore, a distributed peer-to-peer storage system which provides high reliability and availability by the use of advanced caching and coding techniques.

Network Storage Services

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  Xen and the Art of Virtualization. P. Barham, B. Dragovic, K. Fraser, S.T.m Harris, A. Ho, R. Neugebar, I. Pratt, A. Warfield. Proceedings of the ACM Symposium on Operating Systems Principles (SOSP), October 2003
  
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  Language support for lightweight transactions. T. Harris, K. Fraser. In the 18th ACM SIGPLAN Conference on Object-Oriented Programming, Systems, Languages, and Applications (OOPSLA-2003), October 2003.
  
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  Design choices for language-based transactions. T. Harris Technical Report UCAM-CL-TR-572, August 2003