Freiburg i. Br., Univ., Diss., 2005.

Streaming multimedia content over the IP-network is poised to be the dominant Internet traffic for the coming decade, predicted to account for more than 91% of all consumer traffic in the coming years. Streaming multimedia content ranges from Internet television (IPTV), video on demand (VoD), peer-to-peer streaming, and 3D television over IP to name a few. Widespread acceptance, growth, and subscriber retention are contingent upon network providers assuring superior Quality of Experience (QoE) on top of todays Internet. This work presents the first empirical understanding of Internet’s video-QoE capabilities, and tools and protocols to efficiently infer and improve them. To infer video-QoE at arbitrary nodes in the Internet, we design and implement MintMOS: a lightweight, real-time, noreference framework for capturing perceptual quality. We demonstrate that MintMOS’s projections closely match with subjective surveys in accessing perceptual quality. We use MintMOS to characterize Internet video-QoE both at the link level and end-to-end path level. As an input to our study, we use extensive measurements from a large number of Internet paths obtained from various measurement overlays deployed using PlanetLab. Link level degradations of intra– and inter–ISP Internet links are studied to create an empirical understanding of their shortcomings and ways to overcome them. Our studies show that intra–ISP links are often poorly engineered compared to peering links, and that iii degradations are induced due to transient network load imbalance within an ISP. Initial results also indicate that overlay networks could be a promising way to avoid such ISPs in times of degradations. A large number of end-to-end Internet paths are probed and we measure delay, jitter, and loss rates. The measurement data is analyzed offline to identify ways to enable a source to select alternate paths in an overlay network to improve video-QoE, without the need for background monitoring or apriori knowledge of path characteristics. We establish that for any unstructured overlay of N nodes, it is sufficient to reroute key frames using a random subset of k nodes in the overlay, where k is bounded by O(lnN). We analyze various properties of such random subsets to derive simple, scalable, and an efficient path selection strategy that results in a k-fold increase in path options for any source-destination pair; options that consistently outperform Internet path selection. Finally, we design a prototype called source initiated frame restoration (SIFR) that employs random subsets to derive alternate paths and demonstrate its effectiveness in improving Internet video-QoE.

The thesis describes the course and results of the research into the field of Harm Reduction (HR) through the internet websites in the Czech language. Nowadays the internet forms an inseparable part of most people's lives from all social classes. This fact is reflected in the interests of both service providers for drug users and laymen interested in drug issues. Unfortunately, according to current research we do not know much about what information and in which quality and range can people find about drug Harm reduction on the internet. Therefore, the aim of this thesis was to identify and evaluate internet websites in the field of harm reduction intervention focused on the users of illegal drugs in the Czech Republic. Internet websites were evaluated not only with respect to the contents and range of the information provided but also with respect to topicality, functionality and objectivity. What was found were 13 Czech complex websites, 7 professional HR organisations and also 6 non-professional HR websites. The websites of professional organisations in most cases fulfilled the essential criteria of authority, objectivity and topicality. Among non-professional websites there were high-quality ones containing a wide range of information and correct approach to drug issues but there were also two...