Network and user-level traffic adaptation for collaborative-workspace applications

Abstract: Collaborative workspace applications based on IP-multicast offer a scalable solution for computer supported human-to-human communication. Although Internet-wide multicast access is not a reality, multicast deployment is steadily increasing on subnets, such as corporate and campus networks. Over the past few years this has allowed these applications to begin making headway into work and educational environments. One of the primary drawbacks that the current generation of these applications suffer from is that they generally use simple data transport protocols, which leads to inefficient use of network resources. The primary reason for this is that while a great deal of progress has been made in the area of multicast transport, additional work is needed that can put this research in the context of real-world requirements and usage scenarios, which will enable effective application-level-framing. The work in this thesis focuses on this problem, in that it discusses data transport in the context of a specific industrial collaborative-workspace and shows how improvements can be made in terms of data recovery and bandwidth adaptation, which will save network resources and improve the quality of media reception experienced by users. Thus, an industrial partner, Marratech AB, which specializes in collaborative workspaces, was consulted throughout the work conducted in the thesis and was valuable in helping identify real-world requirements for the protocols and ideas presented. In addition, prototyping relating to the work has been built into Marratech software. The thesis explores the two primary areas of data transport in this context, these being reliability and bandwidth adaptation. In the area of reliability the thesis explores how to generate the necessary feedback for data recovery in a novel and efficient way that does not interfere with calculations for available bandwidth, which is a drawback that many other reliable multicast protocols suffer from. In addition, the thesis explores how to integrate data semantics into the recovery process in order to minimize unnecessary packet retransmissions and control traffic. In the area of bandwidth adaptation, the feedback scheme mentioned above is used in order to adapt the bandwidth consumption of reliable media, such as whiteboards and shared web-browsers, to levels that are ''friendly'' with traditional TCP-based applications. In addition, a bandwidth sharing scheme for the video-streams used in collaborative workspaces is presented that identifies the most important senders in the session and allocates them with a larger share of the session bandwidth.