A Multipoint Communication Architecture for End-to-End Quality of Service Guarantees

The developments in information technology of the last years have led to major advances in high-speed networking, multimedia capabilities for workstations and also distributed multimedia applications. In particular, multimedia applications for computer supported cooperative work have been developed that allow groups of people to exchange information and to collaborate and cooperate joint work. However, existing communication systems do not provide end-to-end guarantees for multipoint communication services which are needed by these applications. In this thesis, a communication architecture is described that offers end-to-end performance guarantees in conjunction with flexible multipoint communication services. The architecture is implemented in the Multipoint Communication Framework (MCF) that extends the basic communication services of existing operating systems. It orchestrates endsystem and network resources in order to provide end-to-end performance guarantees. Furthermore, it provides multipoint communication services where participants dynamically join and leave. The communication services are implemented by protocol stacks which form a three layer hierarchy. The topmost layer is called multimedia support layer. It accesses the endsystem's multimedia devices. The transport layer implements end-to-end protocol functions that are used to forward multimedia data. The lowest layer is labelled multicast adaptation layer. It interfaces to various networks and provides a multipoint-to-multipoint communication service that is used by the transport layer. Each layer contains a set of modules that implement a single protocol function. Protocol stacks are dynamically composed out of modules. Each protocol uses a single module on each layer. Applications specify their service requirements as Quality of Service (QoS) parameters. MCF maps these QoS parameters to the above mentioned layers, where they are used to calculate the needed resources. A resource manager reserves memory, CPU and multimedia devices in the endsystem. Access to the CPU is provided by a real-time scheduler for periodic tasks, which executes the protocols. The reservation of network resources is delegated to the network resource manager. MCF orchestrates endsystem and network resources in order to provide a guaranteed service covering the whole path from multimedia device to multimedia device. The evaluation of MCF shows that the proposed architecture results in an easy to use and efficient solution. The dynamic composition of protocol stacks offers high flexibility and allows applications to transport any multimedia data over any network. Resource reservations provide the performance guarantees needed for continuous media such as audio or video.