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In this paper we present a CDN‐based system, namely the COMODIN system, which is a media on‐demand platform for synchronous cooperative work which supports an explicitly‐formed cooperative group of distributed users with the following integrated functionalities: request of an archived multimedia session, sharing of its playback, and collaboration through questioning. The server‐side architecture of the COMODIN system is organized into two integrated planes: the Base plane, which consists of a streaming CDN providing media streaming, and the Collaborative plane, which provides the collaborative playback service. At the client‐side, the system centers on a Java‐based application which interfaces the cooperative group of users.

The convergence of multimedia, virtual reality and the Internet is promoting low‐cost multimedia virtual environments which are easily accessible to large network communities. These environments, which facilitate usability and enhance user experience, are very suitable for supporting user‐oriented application domains such as e‐learning and entertainment. This paper presents a multimedia virtual environment, namely the Virtual Video Gallery, an advanced, distributed media on‐demand system which is browsable through a virtual world. By taking a virtual walk inside the gallery, the user can interactively select, preview, watch and control multimedia sessions. While the user‐centred design of the system relies on UML‐based modelling techniques, system implementation is obtained by the integration of Java, VRML and Web‐based technologies. In order to evaluate the user‐oriented effectiveness of the Virtual Video Gallery and compare it to currently available Internet‐based MoD systems, the usability testing of the system was established for deriving both summative and formative usability data.

To date e‐Learning material has usually been accessed and delivered through a central web server. As the number of users, the amount of information, the frequency of accesses and the volume of data increase, together with the introduction of multimedia streaming applications, a decentralized content distribution architecture is necessary. In this paper we propose the adaptation of the well‐known scalable Content Distribution Networks (CDN) schema for media streaming supported e‐Learning using a novel architecture named COMODIN SCDN (COoperative Media On‐Demand on the InterNet ‐ Streaming Content Distribution Network). COMODIN SCDN utilises surrogates as edge content delivery nodes, incorporates a redirection mechanism able to route requesting clients to the closest copy of the content, encompasses distributed content delivery and management mechanisms to improve the speed, reliability, and scalability of user access to prevent flash‐crowds. Preliminary results in testbeds have shown that COMODIN SCDN increases the efficacy of information distribution through intra and inter‐campus area netwoks. This overlay network will provide learners and educators a scalable, balanced and expeditious access to e‐Learning contents.