Logotipo CRC2010
Cidade de Braga

10ª Conferência sobre Redes de Computadores

11 e 12 de Novembro de 2010, Universidade do Minho, Braga

CRC2010 Programa 3ª Sessão - Aplicações e Serviços I

Quinta-feira, 11.Novembro.2010

16h50-18h30 3ª Sessão - Aplicações e Serviços I

Moderador: Teresa Vazão, IST

A Simple Metric for Predicting Video Quality of Experience
Laercio Cruvinel, Teresa Vazão, IST


Quality of Experience evaluation for video and audio transmissions over the Internet has gained an increased attention, due to the importance of promoting customer satisfaction. In this paper we propose a framework for predicting the end user's Quality of Experience in a test environment that comprises an evaluation process and a simple metric, simulating a lossy or congested network having a mechanism of traffic engineering to differentiate among relative importances of the transmitted packets. The results obtained have confirmed the validity of our approach in the context of the assumed premises, showing that it is possible to achieve similar results to the ones that are obtained when the video subjective quality is resource-intensively assessed by the VQM metric.

Index Terms: QoE, Video Quality

Jogos On-line: Estudo sobre QoE e QoS
João Carvalho, João Oliveira, Paulo Carvalho, UM


Este artigo apresenta um estudo de serviços actuais e emergentes suportados na Internet em torno dos jogos online. São abordados os requisitos de desempenho que os jogos mais exigentes impõem às redes TCP/IP, a qualidade de serviço prestada pelos ISPs e também a qualidade experienciada pelos jogadores em Portugal.

A realização deste estudo assenta no contacto directo com alguns dos principais produtores de jogos para obter informações quanto ao seu funcionamento, em entrevistas a jogadores para saber as suas opiniões sobre os serviços que utilizam, discutindo-se ainda possíveis soluções com profissionais que trabalham para fornecedores de serviços de Internet em Portugal.

Neste contexto, apresentam-se os resultados da análise e do estudo efectuado, identificam-se e quantificam-se os principais parâmetros de QoS, e propõem-se possíveis soluções para melhorar tanto a qualidade de serviço como a qualidade de experiência deste tipo de aplicações.

Index Terms: Jogos Online, QoS, QoE

WebStream - Streaming the web
Dina Pires, Artur Arsénio, IST


Video content is dynamic and contains information that changes in time and space. However, video does not offer a similar level of interactivity to that achieved with the Internet. Since video and web are widely used, it is reasonable to consider that they can be successfully integrated. This work presents a system that integrates web and video contents. The main goal is to provide one interactive solution that allows users to access the two kinds of information simultaneously, having at the same time an active role while watching contents.

The proposed solution presents an innovative and attractive integration of contents for users using the MPEG-4 standard. The architecture is composed essentially by components on a serving module and on a client module. The system was tested and validated with success.

Index Terms: HyperVideo, Web, Video, MPEG-4, Video Browsing, Interactivity, Streaming

Scalable Video Distribution in Peer-to-Peer Architecture
Roberto Nunes, Rui Cruz, Mário Nunes, IST


The combination of Scalable Video Coding and Peer-to-Peer networks is a potential area of innovation in terms of video streaming on the Internet. Applications for sharing files, such as BitTorrent, have been broadly developed and nowadays they cater for the majority of the Internet traffic, adding the need for the exploration of real-time streaming services based on these networks. Several Peer-to-Peer streaming techniques have been deployed, but very few explore bandwidth adaptation, support of diverse terminal and computational setups, adequate incentives for contributing in a multi-source streaming environment or maintenance of a stable perceived video quality. This paper presents the design and implementation of a Scalable Video Coding and Peer-to-Peer Player prototype that uses a novel adaptive algorithm, the Prioritized Sliding Window, that addresses all these related issues in terms of maintaining a stable QoS/QoE. The evaluation of the prototype shows that it achieves a robust real-time streaming service, supports several terminal setups, adapts bandwidth to various access networks and discourages free-riders in the network.

Index Terms: BitTorrent, Scalable Video, Peer-to-Peer, Adaptive Streaming

Social Networks for Cycle-Sharing
Nuno Apolónia, Paulo Ferreira, Luís Veiga, IST


The growth of the Internet, and consequently the number of interconnected computers is the basis for the global distributed computing and public-resource sharing. Meaning that, these resources have been used for computation intensive projects that could not be completed in a short time frame, sometimes not even in supercomputers which are not widely available.

Furthermore, the Internet is overwhelmed by social connectivity. Internet users make use of Social networks to interact and share information, knowledge and services with each other. This paper presents an overview of Peer-to-Peer networks and Grids, to understand their advantages and problems. So that, we can grasp the fundamental ideas that sprout the global distributed computing and the problem of locating resources and services efficiently.

We also analyze Social networks and social interactions to understand how they can be explored for other uses rather than what they were initially created for.

In the last sections we propose the development of a web-enabled platform, called Social Networks for Cycle-Sharing (SNCS), that uses Social networks as a starting point for resource and service discovery and integrating it with Ginger Middleware for distributed computing of tasks.

Index Terms: Social networks, resource discovery, Peer-to-Peer, public-resource sharing, global distributed computing.

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