Quality of experience-centric management of adaptive video streaming services : status and challenges

Video streaming applications currently dominate Internet traffic. Particularly, HTTP Adaptive Streaming ( HAS) has emerged as the dominant standard for streaming videos over the best-effort Internet, thanks to its capability of matching the video quality to the available network resources. In HAS, the video client is equipped with a heuristic that dynamically decides the most suitable quality to stream the content, based on information such as the perceived network bandwidth or the video player buffer status. The goal of this heuristic is to optimize the quality as perceived by the user, the so-called Quality of Experience (QoE). Despite the many advantages brought by the adaptive streaming principle, optimizing users' QoE is far from trivial. Current heuristics are still suboptimal when sudden bandwidth drops occur, especially in wireless environments, thus leading to freezes in the video playout, the main factor influencing users' QoE. This issue is aggravated in case of live events, where the player buffer has to be kept as small as possible in order to reduce the playout delay between the user and the live signal. In light of the above, in recent years, several works have been proposed with the aim of extending the classical purely client-based structure of adaptive video streaming, in order to fully optimize users' QoE. In this article, a survey is presented of research works on this topic together with a classification based on where the optimization takes place. This classification goes beyond client-based heuristics to investigate the usage of server-and network-assisted architectures and of new application and transport layer protocols. In addition, we outline the major challenges currently arising in the field of multimedia delivery, which are going to be of extreme relevance in future years

A survey on network game cheats and P2P solutions

The increasing popularity of Massively Multiplayer Online Games (MMOG) - games involving thousands of players participating simultaneously in a single virtual world - has highlighted the scalability bottlenecks present in centralised Client/Server (C/S) architectures. Researchers are proposing Peer-to-Peer (P2P) game technologies as a scalable alternative to C/S; however, P2P is more vulnerable to cheating as it decentralises the game state and logic to un-trusted peer machines, rather than using trusted centralised servers. Cheating is a major concern for online games, as a minority of cheaters can potentially ruin the game for all players. In this paper we present a review and classification of known cheats, and provide real-world examples where possible. Further, we discuss counter measures used by C/S game technologies to prevent cheating. Finally, we discuss several P2P architectures designed to prevent cheating, highlighting their strengths and weaknesses

Cheating in networked computer games: a review

The increasing popularity of Massively Multiplayer Online Games (MMOG) - games involving thousands of players participating simultaneously in a single virtual world - has highlighted the scalability bottlenecks present in centralised Client/Server (C/S) architectures. Researchers are proposing Peer-to-Peer (P2P) architectures as a scalable alternative to C/S; however, P2P is more vulnerable to cheating as it decentralises the game state and logic to un-trusted peer machines, rather than using trusted centralised servers. Cheating is a major concern for online games, as a minority of cheaters can potentially ruin the game for all players. In this paper we present a review and classification of known cheats, and provide real-world examples where possible. Further, we discuss counter measures used by C/S architectures to prevent cheating. Finally, we discuss several P2P architectures designed to prevent cheating, highlighting their strengths and weaknesses

Design Issues for Peer-to-Peer Massively Multiplayer Online Games.

Massively Multiplayer Online Games (MMOGs) are increasing in both popularity and scale, and while classical Client/Server (C/S) architectures convey some benefits, they suffer from significant technical and commercial drawbacks. This realisation has sparked intensive research interest in adapting MMOGs to Peer-to-Peer (P2P) architectures. This paper articulates a comprehensive set of six design issues to be addressed by P2P MMOGs, namely Interest Management (IM), game event dissemination, Non-Player Character (NPC) host allocation, game state persistency, cheating mitigation and incentive mechanisms. Design alternatives for each issue are systematically compared, and their interrelationships discussed. We further evaluate how well representative P2P MMOG architectures fulfil the design criteria

Network Awareness of P2P Live Streaming Applications

Early P2P-TV systems have already attracted millions of users, and many new commercial solutions are entering this market. Little information is however available about how these systems work. In this paper we present large scale sets of experiments to compare three of the most successful P2P-TV systems, namely PPLive, SopCast and TVAnts. Our goal is to assess what level of "network awareness" has been embedded in the applications, i.e., what parameters mainly drive the peer selection and data exchange. By using a general framework that can be extended to other systems and metrics, we show that all applications largely base their choices on the peer bandwidth, i.e., they prefer high-bandwidth users, which is rather intuitive. Moreover, TVAnts and PPLive exhibits also a preference to exchange data among peers in the same autonomous system the peer belongs to. However, no evidence about preference versus peers in the same subnet or that are closer to the considered peer emerges. We believe that next-generation P2P live streaming applications definitively need to improve the level of network-awareness, so to better localize the traffic in the network and thus increase their network-friendliness as wel

Network Awareness of P2P Live Streaming Applications: A Measurement Study

Abstract: Early P2P-TV systems have already attracted millions of users, and many new commercial solutions are entering this market. Little information is however available about how these systems work, due to their closed and proprietary design. In this paper, we present large scale experiments to compare three of the most successful P2P-TV systems, namely PPLive, SopCast and TVAnts. Our goal is to assess what level of "network awareness" has been embedded in the applications. We first define a general framework to quantify which network layer parameters leverage application choices, i.e., what parameters mainly drive the peer selection and data exchange. We then apply the methodology to a large dataset, collected during a number of experiments where we deployed about 40 peers in several European countries. From analysis of the dataset, we observe that TVAnts and PPLive exhibit a mild preference to exchange data among peers in the same autonomous system the peer belongs to, while this clustering effect is less intense in SopCast. However, no preference versus country, subnet or hop count is shown. Therefore, we believe that next-generation P2P live streaming applications definitively need to improve the level of network-awareness, so to better localize the traffic in the network and thus increase their network-friendliness as well

Streaming of Plants in Distributed Virtual Environments

International audienceJust as in the real world, plants are important objects in virtual world for creating pleasant and realistic environments, especially those involving natural scenes. As such, much effort has been made in realistic modeling of plants. As the trend moves towards networked and distributed virtual environment, however, the current models are inadequate as they are not designed for progressive transmissions. In this paper, we fill in this gap by proposing a progressive representation for plants based on generalized cylinders. To facilitate the transmission of the plants, we quantify the visual contribution of each branch and use this weight in packet scheduling. We show the efficiency of our representations and effectiveness of our packet scheduler through simulations