Dick Schefström

mStar: enabling collaborative applications on the Internet

Distributed, real-time multimedia applications on the Internet permit users to cooperate in new and more interesting ways for collaborative teamwork and net-based learning. The mStar environment features an agent-based architecture, implemented in Java, which preserves compatibility with the dominant Mbone paradigm for IP multicast. The shared software environment provides an integrated solution for generating, presenting, scoring, and editing media in collaborative applications. In particular, mStar supports developers in creating distributed, real-time multimedia software applications such as e-meetings. mStar enhances both distance education and collaborative teamwork by presenting a uniform user interface for real-time audio and video, shared whiteboard, char, voting, and distributed Web-based presentations. The system also supports on-demand recording and session playback.

Lightweight application level multicast tunnelling using mTunnel

This paper presents a system, named mTunnel, for application level tunnelling of IP-multicast traffic in a lightweight manner, where the end-user is responsible for deciding which MBone-sessions and which IP-multicast groups to tunnel. mTunnel is primarily designed for easy deployment and easy-to-manage tunnelling. Information about currently tunnelled sessions and control of mTunnel is provided through a Web-interface. To save bandwidth, tunnelled streams can be transcoded on the media level and traffic sent through the tunnel can be compressed by grouping several packets together and using statistical compression. The overall bandwidth reduction achieved, without modifying the media itself, has been measured to be between 5% and 14%, depending on the traffic and media type.

The mWeb presentation framework

Abstract This paper presents a framework for bringing the MBone and the World-Wide Web closer together by introducing real-time distribution of HTML-pages and synchronization of WWW-browsers. This framework will enable distributed presentations of WWW-material using the mWeb application. Distribution is done using two new protocols, Scalable Reliable Real-time Transport Protocol — SRRTP and Scalable Reliable File Distribution Protocol — SRFDP. Synchronization is achieved using the WebDesk Control Bus, which allows for scalable messaging in large groups of programs and hosts. This paper also presents how the mWeb application can be used for programmed presentations resulting in a television-like Web-TV. The mWeb framework also includes support for creating HTML-slides and the usage of semantic remote-pointers.

Real-time control and management of distributed applications using IP-multicast

A central issue within any distributed computer environment is how to control and manage running applications. This paper presents an implementation of a framework for control and management of distributed applications and components using IP-multicast. The framework allows for easy and scalable control of single applications, groups of applications or parts of applications using a new agent-based architecture. Messaging is done using the control bus and the scalable reliable real-time transfer protocol for reliable distribution of data. The paper presents how this framework is integrated into Java-based applications and how developers specify access points. The paper also presents an application called multicast Manager, mManager, a Java implementation that provides a user interface to the framework. The mManager allows administrators to get an overview of currently running applications and if necessary control these applications. The paper presents example usage scenarios where the framework is used to create bandwidth-adaptive applications and better group awareness.

The CDT mStar environment: scalable distributed teamwork in action

This paper presents the mStar environment, which creates an environment for truly a mChat, which allows for text based group chat; mVote, which allows for distributed voting and mWeb for shared WWW objects. These are all desktop and IP-multicast based and symmetric. The mStar environment also includes mh4OD, which is a VCR-like tool for recording and playback of teamwork sessions, and mTunne1, which is an application for handling IP-multicast traffic on narrow links in the network (such as ISDN/modem) and network segments that does hot support IP:multicast.. It allows for scaling and tranrforming of the network based data in various ways. KepOrdS: IP-multicast, desktop conferencing, distributed presentations, digital recoding, teamwork, distance education, better-than-being-there.

mTunnel: A Multicast Tunneling System with a User Based Quality-of-Service Model

This paper presents a system, called mTunnel, for application level tunneling of multicast traffic in a lightweight manner, where the end-user is responsible for deciding which MBone-sessions and multicast groups to tunnel. mTunnel is primarily designed for easy deployment and easy-to-manage tunneling. Therefore it runs as an user application and does not need access to restricted system resources.

A framework for management and control of distributed applications using agents and IP-multicast

As more and more applications on the Internet become network aware the need and possibility to remotely control them becomes larger. This paper presents a framework for control and management of distributed applications and components. This is done using IP-multicast and an agent based application architecture. The target of the framework is to allow for resource discovery of both controllable elements and available control points in the these elements as well as real-time control. All this is done in scalable and secure way based on IP-multicast and asymmetric cryptography. The presented framework is also independent of the underlying transport mechanism to allow for flexibility and easy deployment. The framework bandwidth usage and introduced control delay is presented. Details on the reference implementation of the framework and example usage scenarios where the framework is used to create bandwidth adaptive applications and better group awareness is also presented.

Distributed education using the mStar environment

The mStar environment for distributed education utilizes the WWW and IP-multicast to enable teacher-student collaboration over large geographic distances. Several educational projects, spanning fro ...