In modern and future parallel and distributed processing, a large part of computation overhead comes from communication. This can be minimized if the network protocol offers the user services that are aimed at specific types of communication used in these applications. Other important properties of distributed processing applications are time-deterministic latency and guarantees to meet deadlines. Moreover, an important trend is to implement distributed real-time applications on top of standard Ethernet based networks. Therefore, in this thesis, we focus on developing and analyzing how to efficiently support real-time communication services for distributed computing applications over switched Ethernet. The network architecture currently assumed is a switched Ethernet network with only one switch.

The work has resulted in proposed Switched Ethernet networks that offer additional features for parallel and distributed real-time processing. An active Ethernet switch concept is proposed to provide efficient support for different user services, including many-to-many communication and other group communication services with high traffic volumes of short messages. Meanwhile, the real-time support for these special communication patterns is addressed by incorporating deadline-based scheduling in the switch and the end nodes.

Moreover, this thesis addresses real-time services by proposing an alternative solution. In this proposal, the Earliest Deadline First (EDF) algorithm is only used in the source nodes to support real-time traffic with a guaranteed bit rate and end-to-end worst-case delay bound. The thesis also reports a feasibility analysis for hard real-time traffic, which also produces figures on the minimum buffer sizes in the switch to be able to guarantee real-time demands. Meanwhile, differentiation of heterogeneous traffic is considered in the proposed system by placing traffic into several priority classes with distinctly different QoS levels.

The performance of the proposed methods is evaluated in simulations and calculations. It is shown that the different Ethernet extensions, in many cases, are efficient choices for distributed computing systems.