Contributions published at Communication Systems Group (Burkhard Stiller)

One of the main tasks and critical challenges that enterprises are facing nowadays is the supply and publication of relevant content to the right target audiences, in the right place and time. Often enterprise content is published to a variety of media types and the volumes of content to be published are constantly growing. Rising expectations of the consumers and the legal-basis increase the requirements regarding quality, availability and timeliness of content. Therefore, the quick and efficient creation and publication of content has become a critical factor for the success of every enterprise. Content reuse and automation of publication processes are the essential elements for a technological answer to this challenge and have become widely attended topics. This diploma thesis has been accomplished at the Swiss National Bank (SNB), whose existing solution for the publication of content to the Internet website has no longer been able to satisfy the rising requirements. The publication process as well as its underlying architecture has had to be renewed. The developed architecture does not only implement an improved degree of automation but additionally enhances efficiency through organizational improvements in the publication process. Authors in the business units are enabled to publish content on their own and so the process' central bottleneck – the webmaster who conducted the necessary technical steps for most publications in the redeemed solution – is eliminated. This is made possible by an automatism that creates HTML webpages from standard documents (MS Word) provided by the authors. A further important improvement is achieved through an optimization of the possibilities for content reuse. ""Reuse"" means that the same content may be displayed or used in another way at multiple locations. Instead of creating and maintaining this content redundantly, it is created only once and stored in a central repository. From there, it is referenced in all places, in which it is to be reused. In other words, different ""views"" on the same content are established in those places. For a practical implementation of the concept, content must necessarily be maintained in a well-structured central repository and be supplemented with suitable metadata. In this way, authors may link and reuse specific content manually in their documents, but also automated procedures based on pre-configured linkages are possible. Hence, the implemented solution contains both automated and manual procedures for content reuse. The provided solution has been designed specifically for the needs, the information architecture, the system infrastructure and the organization of the SNB. Consequently, in order to reuse it in other environments it would have to be adapted. Nevertheless, it can serve as a valuable conceptual model for the automation of web-publication and the reuse of electronic content.

Peer-To-Peer (P2P) architectures have become a very successful networking paradigm over the last decade. For what ever reason applied, they support efficient distribution of resources and are stable against disturbances such as denial-of-service-attacks or local network failures. Nonetheless, the P2P paradigm is still young and shows teething problems in a network environment that was originally designed for other purposes. In this context, Network Address Translation (NAT) is a widely used technique to connect local area networks with the public internet. While it works very well for networking applications following the traditional client/server paradigm, it poses a serious problem for P2P networks. Many of today’s P2P applications require manual device configuration to work properly with NAT devices. This is complicated and error-prone, especially for the average computer user. Misconfiguration can even introduce severe security issues to the local network. In addition, the group of internet users behind a NAT device is expected to grow to an important—but by many P2P applications neglected—resource for distributed computing-power or storage space. For all these reasons, the diploma thesis at hand will present necessary concepts to enable future P2P applications to handle NAT devices efficiently and in a configuration-free way. These concepts are then applied and collected in a NAT traversal framework for P2P developers. In addition, a simple chat application using this framework will provide a simple example of how the framework can be used.

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The key aim of this thesis work is to design and prototypically implement the Accounting module for an AAA server, based on the Generic AAA Architecture defined in RFC 2903 and Diameter protocol specifications. The resulting protocol and architecture shall provide a solution for offering accounting services to a Mobile Grid. It will also be used at a later stage together with various charging models for creating a charging mechanism for future mobile grids. A mobile grid environment, by its heterogenos nature brings new challenges to all the tree A-s in a traditional AAA environment. Regarding the accounting proccess, new types of resources have to be accounted for which require new parameters that have to be present in accounting records. Besides the traditional accounting of time, bytes, and packets, a grid service might need to account for CPU usage, memory consumption, or even accessed/containing information. The accounting module shall provide generic interfaces for possibly different monitoring entities that adapt to the type of resource being accounted for. The access to accounted for data shall be secure and reliable. Secure in this context means that accounted for records for a certain service can be created by certain entities that are aproved by that service provider. This requirement can be realized using X.509 certificates or other kind of credential tokens. Encryption of accounting messages shall be offered as a communication option between the AAA client and the AAA server. Reliability refers to the posibility of retreiving the accurate accounting information for a certain service/resource usage for charging consumptions.

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