A Utility-based QoS Model for Emerging Multimedia Applications

Existing network QoS models do not sufficiently reflect the challenges faced by high-throughput, always-on, inelastic multimedia applications. In this paper, a utility-based QoS model is proposed as a user layer extension to existing communication QoS models to better assess the requirements of multimedia applications and manage the QoS provisioning of multimedia flows. Network impairment utility functions are derived from user experiments and combined to application utility functions to evaluate the application quality. Simulation is used to demonstrate the validity of the proposed QoS model

Fine Grained Component Engineering of Adaptive Overlays: Experiences and Perspectives

Recent years have seen significant research being carried out into peer-to-peer (P2P) systems. This work has focused on the styles and applications of P2P computing, from grid computation to content distribution; however, little investigation has been performed into how these systems are built. Component based engineering is an approach that has seen successful deployment in the field of middleware development; functionality is encapsulated in ‘building blocks’ that can be dynamically plugged together to form complete systems. This allows efficient, flexible and adaptable systems to be built with lower overhead and development complexity. This paper presents an investigation into the potential of using component based engineering in the design and construction of peer-to-peer overlays. It is highlighted that the quality of these properties is dictated by the component architecture used to implement the system. Three reusable decomposition architectures are designed and evaluated using Chord and Pastry case studies. These demonstrate that significant improvements can be made over traditional design approaches resulting in much more reusable, (re)configurable and extensible systems

Analysis of searching mechanisms in hierarchical p2p based overlay networks

Proceedings of: The 6th Annual Mediterranean Ad Hoc Networking Workshop (Med Hoc Net 2007. (Corfu, Greece), June 2007This work presents a study of searching mechanisms in Peer-to-Peer (p2p) networks. The aim of this research line is to analyse cross-searching mechanisms that will allow the hierarchical interconnection of p2p networks. A set of relevant metrics for interconnection scenarios are defined to evaluate scalability, robustness and routing latency.This work has been partially supported by the European Union under the IST Content (FP6-2006-IST-507295) project and by the Madrid regional government under the Biogridnet (CAM, S-0505/TIC-0101) project.Publicad

Analysis and characterisation of botnet scan traffic

Botnets compose a major source of malicious activity over a network and their early identification and detection is considered as a top priority by security experts. The majority of botmasters rely heavily on a scan procedure in order to detect vulnerable hosts and establish their botnets via a command and control (C&C) server. In this paper we examine the statistical characteristics of the scan process invoked by the Mariposa and Zeus botnets and demonstrate the applicability of conditional entropy as a robust metric for profiling it using real pre-captured operational data. Our analysis conducted on real datasets demonstrates that the distributional behaviour of conditional entropy for Mariposa and Zeus-related scan flows differs significantly from flows manifested by the commonly used NMAP scans. In contrast with the typically used by attackers Stealth and Connect NMAP scans, we show that consecutive scanning flows initiated by the C&C servers of the examined botnets exhibit a high dependency between themselves in regards of their conditional entropy. Thus, we argue that the observation of such scan flows under our proposed scheme can sufficiently aid network security experts towards the adequate profiling and early identification of botnet activity

Sampling cluster endurance for peer-to-peer based content distribution networks

Several types of Content Distribution Networks are being deployed over the Internet today, based on different architectures to meet their requirements (e.g., scalability, efficiency and resiliency). Peer-to-peer (P2P) based Content Distribution Networks are promising approaches that have several advantages. Structured P2P networks, for instance, take a proactive approach and provide efficient routing mechanisms. Nevertheless, their maintenance can increase considerably in highly dynamic P2P environments. In order to address this issue, a two-tier architecture called Omicron that combines a structured overlay network with a clustering mechanism is suggested in a hybrid scheme. In this paper, we examine several sampling algorithms utilized in the aforementioned hybrid network that collect local information in order to apply a selective join procedure. Additionally, we apply the sampling algorithms on Chord in order to evaluate sampling as a general information gathering mechanism. The algorithms are based mostly on random walks inside the overlay networks. The aim of the selective join procedure is to provide a well balanced and stable overlay infrastructure that can easily overcome the unreliable behavior of the autonomous peers that constitute the network. The sampling algorithms are evaluated using simulation experiments as well as probabilistic analysis where several properties related to the graph structure are reveale

Sampling cluster endurance for peer-to-peer based content distribution networks

Several types of Content Distribution Networks are being deployed over the Internet today, based on different architectures to meet their requirements (e.g., scalability, efficiency and resiliency). Peer-to-peer (P2P) based Content Distribution Networks are promising approaches that have several advantages. Structured P2P networks, for instance, take a proactive approach and provide efficient routing mechanisms. Nevertheless, their maintenance can increase considerably in highly dynamic P2P environments. In order to address this issue, a two-tier architecture called Omicron that combines a structured overlay network with a clustering mechanism is suggested in a hybrid scheme. In this paper, we examine several sampling algorithms utilized in the aforementioned hybrid network that collect local information in order to apply a selective join procedure. Additionally, we apply the sampling algorithms on Chord in order to evaluate sampling as a general information gathering mechanism. The algorithms are based mostly on random walks inside the overlay networks. The aim of the selective join procedure is to provide a well balanced and stable overlay infrastructure that can easily overcome the unreliable behavior of the autonomous peers that constitute the network. The sampling algorithms are evaluated using simulation experiments as well as probabilistic analysis where several properties related to the graph structure are reveale

Providing producer mobility support in NDN through proactive data replication

Email Print Request Permissions Named Data Networking (NDN) is a novel architecture expected to overcome limitations of the current Internet. User mobility is one of the most relevant limitations to be addressed. NDN supports consumer mobility by design but fails to offer the same level of support for producer mobility. Existing approaches to extend NDN are host-centric, which conflicts with NDN principles, and provide limited support for producer mobility. This paper proposes a content-centric strategy that replicates and pushes objects proactively, and unlike previous approaches, takes full advantage of NDN routing and caching features. We compare the proposed strategy with default NDN mechanisms regarding content availability, consumer performance, and network overhead. The evaluation results indicate that our strategy can increase the hit rate of objects by at least 46% and reduce their retrieval time by over 60%, while not adding significant overhead

Tap or swipe? Effects of interaction gestures for retrieval of match statistics via second screen on watching soccer on TV

Accessing match statistics through second screen while watching soccer matches on TV has grown into a popular practice. Although early works have shown how gestures on touch screens performed under distracting environments, little is known regarding how specific gestures (swiping and tapping) to retrieve information on second screen affect the viewing experience of soccer games on TV. For this, a mixed-method user study, which included prototype tests of watching short clips of a soccer match, questionnaires and short interviews, was conducted with 28 participants. The results revealed that the number of people who preferred tapping was more than the number of people who favored swiping under two different second screen activity time scenarios i.e. On-Play or Off-Play. However, neither swiping nor tapping yield better performance of recalling verbatim match stats and exact comparisons in both On-Play and Off-Play. Participant evaluations in On-Play and interviews give us clues regarding such difference.</p