We propose a lightweight fault-tolerant multicast and membership service for real-time process groups which may exchange periodic and aperiodic messages. The service supports bounded-time message transport, atomicity, and order for multicasts within a group of communicating processes in the presence of processor crashes and communication failures. It guarantees agreement on membership among the communicating processors, and ensures that membership changes (e.g., resulting from processor joins or departures) are atomic and ordered with respect to multicast messages. We provide the flexibility of an event-triggered approach with the fast message delivery time of time-triggered protocols, such as TTP [14], where messages are delivered to the application immediately upon reception. This is achieved without compromising agreement, order and atomicity properties. In addition to the design and details of the algorithm, we describe our implementation of the protocol using the x-Kernel protocol architecture running on RT Mach 3.0. 1.

FDDI-Based Reconfigurable Networks [1] have an architecture that is suitable for delivering messages that have hard real-time constraints as well as certain fault-tolerance requirements. This architecture uses multiple FDDI networks to connect hosts and provides for automatic reconfiguration to maintain high network bandwidth in spite of faults. An important open problem is how resources in such networks should be managed in order to guarantee that the fault-tolerant real-time requirements of messages are met. This paper presents an efficient and practical solution to this problem. Our solution consists of off-line and on-line components. On-line management deals with run-time manipulation of messages and network resources. A message grouping approach simplifies on-line management. Off-line management deals with message grouping, bandwidth allocation and schedulability verification. Three approaches are investigated: spatial redundancy, temporal redundancy and an integrated approach. I...

This paper describes several existing data link layer protocols that provide real-time capabilities on wired networks, focusing on token-ring and Carrier Sense Multiple Access based networks. Existing modifications to provide better real-time capabilities and performance are also described. Finally the pros and cons regarding the At-Home Anywhere project are discussed.

There is increasing use of distributed computer systems to support real-time applications. The key to successfully developing such systems is to have a communication network which supports the timely delivery of inter-task messages. The main focus of this research is to address some important issues related to guarantees of message deadlines in a communication network. Our effort has concentrated on the timed token ring networks, such as FDDI, where the timed token medium access control (MAC) protocol is employed. Specifically, we studied the problem of guaranteeing synchronous message deadlines by appropriate allocation of the synchronous bandwidths. Synchronous bandwidth, defined as the maximum time for which a node can transmit its synchronous messages every time it receives the token, is a key parameter in the control of synchronous message transmission. To ensure the transmission of synchronous messages before their deadlines, synchronous bandwidths must be properly allocated to i...