Network overload avoidance by traffic engineering and content caching

The Internet traffic volume continues to grow at a great rate, now driven by video and TV distribution. For network operators it is important to avoid congestion in the network, and to meet service level agreements with their customers. This thesis presents work on two methods operators can use to reduce links loads in their networks: traffic engineering and content caching. This thesis studies access patterns for TV and video and the potential for caching. The investigation is done both using simulation and by analysis of logs from a large TV-on-Demand system over four months. The results show that there is a small set of programs that account for a large fraction of the requests and that a comparatively small local cache can be used to significantly reduce the peak link loads during prime time. The investigation also demonstrates how the popularity of programs changes over time and shows that the access pattern in a TV-on-Demand system very much depends on the content type. For traffic engineering the objective is to avoid congestion in the network and to make better use of available resources by adapting the routing to the current traffic situation. The main challenge for traffic engineering in IP networks is to cope with the dynamics of Internet traffic demands. This thesis proposes L-balanced routings that route the traffic on the shortest paths possible but make sure that no link is utilised to more than a given level L. L-balanced routing gives efficient routing of traffic and controlled spare capacity to handle unpredictable changes in traffic. We present an L-balanced routing algorithm and a heuristic search method for finding L-balanced weight settings for the legacy routing protocols OSPF and IS-IS. We show that the search and the resulting weight settings work well in real network scenarios

EMB: Efficient Multimedia Broadcast in Multi-tier Mobile Networks

Multimedia broadcast and multicast services (MBMS) in mobile networks has been widely addressed, however an investigation of such a technology in emerging, multi-tier, scenarios is still lacking. Notably, user clustering and resource allocation are extremely challenging in multi-tier networks, and imperative to maximize system capacity and improve quality of user-experience (QoE) in MBMS. Thus, in this paper we propose a clustering and resource allocation approach, named EMB, which specifically addresses heterogeneous networks and accounts for the fact that multimedia content is adaptively encoded into scalable layers depending on the QoE requirements and channel conditions of the heterogeneous users. Importantly, we prove that our clustering algorithm yields Pareto efficient broadcasting areas, multimedia encoding parameters, and re- source allocation, in a way that is also fair to the users. Fur- thermore, numerical results obtained under realistic conditions and using real-world video content, show that the proposed EMB results in lower churn count (i.e., higher number of served users), higher throughput, and increased QoE, while using fewer network resources

Analyzing the potential benefits of CDN augmentation strategies for internet video workloads

Video viewership over the Internet is rising rapidly, and market pre-dictions suggest that video will comprise over 90 % of Internet traf-fic in the next few years. At the same time, there have been signs that the Content Delivery Network (CDN) infrastructure is being stressed by ever-increasing amounts of video traffic. To meet these growing demands, the CDN infrastructure must be designed, pro-visioned and managed appropriately. Federated telco-CDNs and hybrid P2P-CDNs are two content delivery infrastructure designs that have gained significant industry attention recently. We ob-served several user access patterns that have important implica-tions to these two designs in our unique dataset consisting of 30 million video sessions spanning around two months of video view-ership from two large Internet video providers. These include par-tial interest in content, regional interests, temporal shift in peak load and patterns in evolution of interest. We analyze the impact of our findings on these two designs by performing a large scale measurement study. Surprisingly, we find significant amount of synchronous viewing behavior for Video On Demand (VOD) con-tent, which makes hybrid P2P-CDN approach feasible for VOD and suggest new strategies for CDNs to reduce their infrastructure costs. We also find that federation can significantly reduce telco-CDN provisioning costs by as much as 95%

Popularity Characterization and Modelling for User-generated Videos

User-generated content systems such as YouTube have become highly popular. It is difficult to under- stand and predict content popularity in such systems. Characterizing and modelling content popularity can provide deeper insights into system design trade-offs and enable prediction of system behaviour in advance. Borghol et al. collected two datasets of YouTube video weekly view counts over eight months in 2008/09, namely a “recently-uploaded” dataset and a “keyword-search” dataset, and analyzed the popular- ity characteristics of the videos in the recently-uploaded dataset including the video popularity evolution over time. Based on the observed characteristics, they developed a model that can generate synthetic video weekly view counts whose characteristics with respect to video popularity evolution match those observed in the recently-uploaded dataset. For this thesis, new weekly view count data was collected over two months in 2011 for the videos in the recently-uploaded and keyword-search datasets of Borghol et al. This data was used to evaluate the accuracy of the Borghol et al. model when used to generate synthetic view counts for a much longer time period than the eight month period previously considered. Although the model yielded distributions of total (lifetime) video view counts that match the empirical distributions, significant differences between the model and em- pirical data were observed. These differences appear to arise because of particular popularity characteristics that change over time rather than being week-invariant as assumed in the model. This thesis also characterizes how video popularity evolves beyond the eight month period considered by Borghol et al., and studies the characteristics of the keyword-search dataset with respect to content popu- larity, popularity evolution, and sampling biases. Finally, the thesis studies the popularity characteristics of the videos in the recently-uploaded and keyword-search datasets for which additional view count data could not be collected, owing to the removal of these videos from YouTube

Models, services and security in modern online social networks

Modern online social networks have revolutionized the world the same way the radio and the plane did, crossing geographical and time boundaries, not without problems, more can be learned, they can still change our world and that their true worth is still a question for the future

Modeling channel popularity dynamics in a large IPTV system

Understanding the channel popularity or content popularity is an important step in the workload characterization for modern information distribution systems (e.g., World Wide Web, peer-to-peer file-sharing systems, video-on-demand systems). In this paper, we focus on analyzing the channel popularity in the context of Internet Protocol Television (IPTV). In particular, we aim at capturing two important aspects of channel popularity – the distribution and temporal dynamics of the channel popularity. We conduct in-depth analysis on channel popularity on a large collection of user channel access data from a nation-wide commercial IPTV network. Based on the findings in our analysis, we choose a stochastic model that finds good matches in all attributes of interest with respect to the channel popularity. Furthermore, we propose a method to identify subsets of user population with inherently different channel interest. By tracking the change of population mixtures among different user classes, we extend our model to a multi-class population model, which enables us to capture the moderate diurnal popularity patterns exhibited in some channels. We also validate our channel popularity model using real user channel access data from commercial IPTV network