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An efficient networking technique for synchronous e-learning platforms in corporate environments

A synchronous e-learning platform is an effective way to implement training programs for human resources in large corporations. These organizations are usually dispersed in multiple sites very distant from each other, so transport of multimedia data within an e-learning activity is a true challenge. Usually, multimedia data is delivered using the RTP protocol. In this paper, an optimal transport technique based on a multicast overlay network is proposed. The overlay is made up of multiple servers that operate at the RTP level and combine unicast and multicast transport whenever possible. This technique has proved to be more efficient than a solution based exclusively on unicast delivery.

Autonomic Platform for Synchronous e-Training in Dispersed Organizations

Synchronous e-training of human resources uses conferencing services to support training at the workplace. Multimedia data is interchanged between participants in real-time in a synchronous e-training activity providing an enriched learning experience. Large organizations are usually widely dispersed in several sites, so synchronous e-training activities are especially difficult. Most of the sites constitute multicast islands, as IP multicast is available, so the data transport can use IP multicast within the sites of the organization in order to save bandwidth. In this paper, an autonomic synchronous e-training platform based on standard protocols implementing self-management features such as self-deployment, self-organization and self-healing is proposed. The platform deploys an overlay network composed of Real-time Transport Protocol relays acting as multicast/unicast reflectors. The overlay is automatically reorganized according to the joining and leaving of participants and network failures. The use of standard protocols and a modular design enable the interoperability, extensibility and portability of the platform.

E-pSyLon: a synchronous e-learning platform for staff training in large corporations

Synchronous e-learning is becoming increasingly popular as a tool for developing human resource training plans in large corporations. A synchronous e-training platform has been designed and implemented to explore the possibilities of synchronous e-training in a large corporation. The client tool is used by learners and instructors to collaborate in real-time during e-training activities. It is based on standard protocols also used in voice over IP, which makes it inter-operable with other software and hardware devices. The functionalities offered by the client tool have been chosen based on those provided by commercial tools, but focusing on the specific characteristics of users and network conditions of corporate environments. This facilitates highly interactive synchronous e-training activities. Multimedia configuration of activities is flexible, so participants with different network link capabilities can join activities. The e-training platform has been tested in real e-training activities in ArcelorMittal Spain. The opinions of the users reflect an enhanced learning experience when using the client tool.

Assessing the QoE in Video Services Over Lossy Networks

Quality of experience is of critical importance in streaming video services, because the traditional quality of service cannot represent the quality perceived by viewers. This work evaluates several objective quality metrics under realistic bursty packet loss conditions in the network, with the support of a packet loss model. Alignment of reference and streamed video sequences (with different levels of spatial-temporal information) are also explored as a technique to prevent inaccurate computation of objective metrics due to frame loss. Finally, the correlation between subjective and objective metrics for each motion level and the computing time of metrics are analysed. The most suitable objective metrics to characterize the real degradation in the quality perceived by viewers, for both off-line and real-time assessment, are proposed. The integration of motion, busty packet loss, sequence alignment after frame loss and computing time of metrics are the main contributions of this research work.

Overlay network based on WebRTC for interactive multimedia communications

Real-time interactive communications have become critical for business, e-commerce, e-government and education. Teleconferencing systems have been usually deployed using proprietary and expensive systems. Overlay networks are often used to support multi-point teleconferencing and provide services unavailable in the underlying physical networks. With the advent of WebRTC, real-time communication applications can be implemented directly in the browser without installing custom applications or additional plugins. This paper proposes an overlay network based on WebRTC oriented to interactive multimedia communications. The overlay is organized in four planes for data delivery, signaling, control and floor control. The data distribution relies on a clustered organization of WebRTC clients interconnected through a reflector mesh, where a reflector mixes the streams coming from a single cluster. The overlay also includes self-organization techniques, re-organizing the clusters when clients leave or join. The signaling plane uses the Session Initiation Protocol (SIP) for the negotiation and establishment of media sessions between clients and reflectors. Signaling is centralized in a rendezvous point which is also responsible for re-organizing the data plane. Finally, the floor control plane is responsible for limiting the number of streams in the overlay by sharing the data channels between clients. Ubiquity of the communication services and interoperability with other WebRTC applications are the main advantages of our proposal.

Self-* in Multimedia Communication Overlays

Multimedia Communication Systems (MCSs) usually deploy complex data distribution overlays, making the efficient interchange of multimedia content possible. The time constraints imposed by interactive communications further complicate the management of the data distribution overlays. Many MCSs have the ability to automatically manage the overlay, hence they behave as autonomic computing systems, facing events that imply changes in the relations or in the performance of their members. Self-management characteristics related to organizing the members of the data distribution overlays, balancing resources, and aggregating efforts are present in many MCSs. These characteristics, or self-properties, can be achieved using various techniques, according to the complexity and time constraints of each MCS. The aim of this paper is to classify the techniques implemented in MCSs to achieve self-management characteristics in their overlays. These techniques are classified according to a taxonomy proposed in this work, providing a unified and practical framework for understanding and comparing them.

Security Issues in a Synchronous e-Training Platform

Synchronous e-training is emerging as an alternative for developing human resources training plans in large organizations. Real-time communications are used to emulate face-to-face interaction that occurs in on-campus learning environments. However, the security concerns that a synchronous e-training platform must face may compromise the integrity, availability and confidentiality of corporate information, which may lead to serious economic and legal consequences. The disclosure of corporate information or the unauthorized participation in e-training activities must be prevented. In this paper, the security issues in synchronous e-training are identified, and the threats to a real e-training platform are analyzed. The platform is organized into four virtual networks with different security requirements and vulnerabilities. The platform assumes that multicast communications are available in the underlying corporate network. The threats affecting each element of the platform and their impact on e-training activities are discussed. Finally, a security scheme is proposed fixing the aforementioned vulnerabilities. Digital certificates and encryption algorithms solve most of the vulnerabilities, but other techniques such as access control lists and user skills on security basics are essential. Most of the proposed scheme is applicable to other real-time communication systems, since the e-training platform is built using standard technologies commonly used in voice over IP systems.

Automatic Deployment of a Communication Mesh for Synchronous e-Learning Activities

Synchronous e-learning platforms are frequently used to train the personnel of large corporations. Usually, these corporations are geographically dispersed in multiple sites, so efficient transport of multimedia streams during an e-learning activity is essential. In order to interconnect the groups of participants, it is necessary to deploy a communication mesh. If the number of sites is high, non-automatic deployment of the communication mesh is complex, cumbersome and prone to errors, delaying the startup of e-learning activities. In this paper, an automatic deployment technique based on a centralized server is proposed. This technique continuously updates the composition of the communication mesh, and involves only those sites where there are active participants in the e-learning activity, modifying the mesh topology in function of the joining and leaving of participants. Tests show that the proposed automatic deployment technique makes use of the available bandwidth efficiently.

A self-managed resilient overlay network for interactive multimedia communications

The use of interactive multimedia communications is widespread in business and education, providing an enriched user experience in teleconferencing, distance learning and online meetings. Overlays networks are the underlying mechanisms enabling multipoint communication in interactive multimedia platforms. They must cope with constraints on heterogeneity, scalability and availability of communications, making their deployment and management a true challenge. Thus, several issues might affect the resilience of overlay networks, threatening ongoing communications. Overlay networks usually use self-organization and self-stabilization techniques to achieve resilient communications. Techniques implementing other self-management properties such as self-regulation also help in improving the resilience of the overlay. In this paper, the resilience of a reflector-based overlay network is improved with a self-regulation technique based on media transcoding. This balances the workloads of the reflectors of the overlay avoiding excessive usage of network links. As a result, the overlay is more resilient to failures. Extensive simulations have been carried out, and various media transcoding schemes have been compared, proving that self-regulation techniques improve the resilience of the reflector-based overlay network.

Towards Resilient Synchronous e-Training Platforms

Synchronous e-training is emerging as an alternative for developing human resources training plans in large organizations. However, synchronous e-training platforms must face many issues affecting their resilience. Self-recovering and self-protection software techniques should be implemented to enable the continuity of e-training activities faced with network failures or entities of the platform going down. In this paper, the resilience issues in synchronous e-training are identified, and those presented in a real e-training platform are analyzed. The platform includes a self-optimizing technique to make efficient use of network resources as participants join and leave. Furthermore, various self-recovering and a self-protection techniques are proposed, making possible the continuity of ongoing e-training activities with reduced functionality until the automatic full system recovery. Most of the proposed techniques are applicable to other real-time communication systems, since the e-training platform is built using standard technologies such as SIP and RTP, commonly used in voice over IP systems.