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In this work, some network protocols with Wireshark Protokollanalyser should be observed and described the deal with them. Wireshark is an offshoot of "Ethereal", one of the most popular protocol analyzer. Wireshark analysis network traffic, draws on it and make it clear . For the simulation of the network is used VNUML. Since VNUML can only be used under Linux, andLinux is running as a virtual machine in between to work in Windows to be able to.

Die Entwicklung von Algorithmen im Sinne des Algorithm Engineering geschieht zyklisch. Der entworfene Algorithmus wird theoretisch analysiert und anschließend implementiert. Nach der praktischen Evaluierung wird der Entwurf anhand der gewonnenen Kenntnisse weiter entwickelt. Formale Verifffizierung der Implementation neben der praktischen Evaluierung kann den Entwicklungsprozess verbessern. Mit der Java Modeling Language (JML) und dem KeY tool stehen eine einfache Spezififfkationssprache und ein benutzerfreundliches, automatisiertes Verififfkationstool zur Verfügung. Diese Arbeit untersucht, inwieweit das KeY tool für die Verifffizierung von komplexeren Algorithmen geeignet ist und welche Rückmeldungen für Algorithmiker aus der Verififfkation gewonnen werden können.Die Untersuchung geschieht anhand von Dijkstras Algorithmus zur Berechnung von kürzesten Wegen in einem Graphen. Es sollen eine konkrete Implementation des Standard-Algorithmus und anschließend Implementationen weiterer Varianten verifffiziert werden. Dies ahmt den Entwicklungsprozess des Algorithmus nach, um in jeder Iteration nach möglichen Rückmeldungen zu suchen. Bei der Verifffizierung der konkreten Implementation merken wir, dass es nötig ist, zuerst eine abstraktere Implementation mit einfacheren Datenstrukturen zu verififfzieren. Mit den dort gewonnenen Kenntnissen können wir dann die Verifikation der konkreten Implementation fortführen. Auch die Varianten des Algorithmus können dank der vorangehenden Verififfkationen verifiziert werden. Die Komplexität von Dijkstras Algorithmus bereitet dem KeY tool einige Schwierigkeiten bezüglich der Performanz, weswegen wir während der Verifizierung die Automatisierung etwas reduzieren müssen. Auf der anderenrn Seite zeigt sich, dass sich aus der Verifffikation einige Rückmeldungen ableiten lassen.

A network like the internet is a set of subnets that are connected to each other by a router. A router is a computer, containing multiple network devices to be connected to multiple subnets. So, it is able to forward packages from one subnet to another. A network can be represented as a graph with its routers as vertices and subnets as edges. This graph is called the topology of the network. A packet send to a host outside the own subnet usually will be send first to the so-called default router. This router (like any router) contains a table (the so-called forwarding table) with every subnet. Additionally for each net, the table contains the router through which the subnet can be reached best. So, the packet will be forwarded from router to router until it reaches the destination subnet. On this way every router looks up in its forwarding table for the best next router. A routing protocol takes care of the automatic exchange of informations between the routers to build the forwarding tables and keep them up to date. If the forwarding tables of all routers are up to date the network is called convergent. The time needed to build or update the routing tables is called the convergence time The RIP routing protocol is a well known and well explored distance vector protocol. But there are only few examinations about the convergence properties (e.g. the time needed to converge or the traffic volume produced by the routing messages). This work tries to examine a relationship between the topology properties of a network and the convergence properties of the rip routing protocol. Therefore, over 5000 single measurements were performed and statistically analyzed. Mathematical formulas have been derived from the results that are able to approximate the convergence properties of a network from its topology properties.

So far VNUML (Virtual Network User Mode Linux) has been used by the group for Computer Networks at the University of Koblenz in such a way as to test its own protocol enhancement for RIP (Routing Information Protocol) on strengths and weaknesses. The modified version of RIP is called RMTI (RIP with minimal topology information). In particular, special test scenarios have been used to investigate wether a Count-to-Infinity (CTI) problem can be completely avoided and how quickly the network converges after the failure or breakdown of a router. Tius thesis investigates whether the MTI enhancement also provides for better performance in larger networks. Furthermore, it will be investigated if it is worth using the script tool EDIV ((spanish: Escenarios DIstribuidos con VNUML, english: Distributed Scenarios using VNUML) due to its enhanced scalability and whether the distribution of an XML scenario on several computers has a significant impact on the convergence time. Apart from simulations, test scenarios will be developed and tested in order to generate results about the efficiency and scalability of the Distance Vector Routing Protocol.

The processing of data is often restricted by contractual and legal requirements for protecting privacy and IPRs. Policies provide means to control how and by whom data is processed. Conditions of policies may depend on the previous processing of the data. However, existing policy languages do not provide means to express such conditions. In this work we present a formal model and language allowing for specifying conditions based on the history of data processing. We base the model and language on XACML.

Hybrid automata are used as standard means for the specification and analysis of dynamical systems. Several researches have approached them to formally specify reactive Multi-agent systems situated in a physical environment, where the agents react continuously to their environment. The specified systems, in turn, are formally checked with the help of existing hybrid automata verification tools. However, when dealing with multi-agent systems, two problems may be raised. The first problem is a state space problem raised due to the composition process, where the agents have to be parallel composed into an agent capturing all possible behaviors of the multi-agent system prior to the verification phase. The second problem concerns the expressiveness of verification tools when modeling and verifying certain behaviors. Therefore, this paper tackles these problems by showing how multi-agent systems, specified as hybrid automata, can be modeled and verified using constraint logic programming(CLP). In particular, a CLP framework is presented to show how the composition of multi-agent behaviors can be captured dynamically during the verification phase. This can relieve the state space complexity that may occur as a result of the composition process. Additionally, the expressiveness of the CLP model flexibly allows not only to model multi-agent systems, but also to check various properties by means of the reachability analysis. Experiments are promising to show the feasibility of our approach.

Knowledge compilation is a common technique for propositional logic knowledge bases. A given knowledge base is transformed into a normal form, for which queries can be answered efficiently. This precompilation step is expensive, but it only has to be performed once. We apply this technique to concepts defined in the Description Logic ALC. We introduce a normal form called linkless normal form for ALC concepts and discuss an efficient satisability test for concepts given in this normal form. Furthermore, we will show how to efficiently calculate uniform interpolants of precompiled concepts w.r.t. a given signature.

Dieses Dokument schlägt ein Konzept für eine Personal Key Infrastruktur in iCity vor. Über ein Trust Center (TC) ausgestellte Zertiffkate gewährleisten einen sicheren Schlüsselaustausch mit nachweisbarer Authentisierung des Kommunikationspartners, Abhörsicherheit sowie Unverf älschtheit und Nachweisbarkeit der Nachrichten. Das gemeinsam vertrauensw ürdige TC muss während der Kommunikation nicht erreichbar sein. Es erhält lediglich öffentliche Informationen. Das Konzept stellt mehrere Sicherheitsstufen vor, die sichere Identiffkation und Anonymität unterschiedlich gewichten.

In this thesis a Java program is developed that can be used to visualize networks previously described in configuration files. These networks must consist of layer 2 switches and hosts only. After loading such a configuration file, the program will visualize the network, and the spanning tree algorithm IEEE 802.1D may be started. The program allows the user to modify specific attributes of switches and hosts. The hosts will be able to exchange messages. The switches are realized as threads so that they can run independently and parallel to each other. The absence of central coordination and control prevents the switches from sharing global knowledge. This characteristic renders the implementation closer to the way an actual network functions.

Specifying behaviors of multi-agent systems (MASs) is a demanding task, especially when applied in safety-critical systems. In the latter systems, the specification of behaviors has to be carried out carefully in order to avoid side effects that might cause unwanted or even disastrous behaviors. Thus, formal methods based on mathematical models of the system under design are helpful. They not only allow us to formally specify the system at different levels of abstraction, but also to verify the consistency of the specified systems before implementing them. The formal specification aims a precise and unambiguous description of the behavior of MASs, whereas the verification aims at proving the satisfaction of specified requirements. A behavior of an agent can be described as discrete changes of its states with respect to external or internal actions. Whenever an action occurs, the agent moves from one state to another one. Therefore, an efficient way to model this type of discrete behaviors is to use a kind of state transition diagrams such as finite automata. One remarkable advantage of such transition diagrams is that they lend themselves formal analysis techniques using model checking. The latter is an automatic verification technique which determines whether given properties are satisfied within a model underlying a particular system. In realistic physical environments, however, it is necessary to consider continuous behaviors in addition to discrete behaviors of MASs. Examples of those type of behaviors include the movement of a soccer agent to kick off or to go to the ball, the process of putting out the fire by a fire brigade agent in a rescue scenario, or any other behaviors that depend on any timed physical law. The traditional state transition diagrams are not sufficient to combine these types of behaviors. Hybrid automata offer an elegant method to capture such types of behaviors. Hybrid automata extend regular state transition diagrams with methods that deal with those continuous actions such that the state transition diagrams are used to model the discrete changes of behaviors, while differential equations are used to model the continuous changes. The semantics of hybrid automata make them accessible to formal verification by means of model checking. The main goal of this thesis is to approach hybrid automata for specifying and verifying behaviors of MASs. However, specifying and and verifying behaviors of MASs by means of hybrid automata raises several issues that should be considered. These issues include the complexity, modularity, and the expressiveness of MASs' models. This thesis addresses these issues and provides possible solutions to tackle them.