To guarantee the delivery of real-time messages before their deadline, a real-time channel or connection must be established before the transmission of any real-time messages. During this channel establishment phase, one must first select a route between the source and destination of this channel and then reserve sufficient resources along this route so that the end-to-end delay over the selected route may not exceed the user-specified delay bound.We propose an efficient distributed route-selection scheme that is guaranteed to find a "qualified" route, if any, satisfying the performance requirement of the requested channel without compromising any of the existing guarantees. The proposed scheme can also eliminate the common reliability /performance bottleneck of a centralized route-selection scheme, while improving efficiency over the centralized and other distributed schemes. Simulation results are presented to demonstrate the effectiveness of the proposed distributed route-selection scheme.

The loops resulting from either component failures or load changes in a computer communication network degrade the performance and the adaptability of conventional distributed adaptive routing strategies, such as ARPANET's previous routing strategy (APRS). In this paper, we develop a distributed loopfree routing strategy by adding only one additional piece of information-the total number of minimum-delay paths-to the commonly used routing messages and tables. Most conventional approaches to the looping problem suffer high overheads in time and space because each message must either include the first several nodes of its path or trace the entire path to detect a loop. By contrast, the proposed routing strategy requires only easily obtainable information, yet removes loops completely. It is far more efficient in both time and space than its conventional counterparts, especiallyTable Ifor sparse computer networks. The correctness of the proposed strategy is proved, and several illustrative examples are given. The performance of this strategy is shown to be always better than, or at least as good as, that of APRS and any multiorder routing strategies, where the order of a routing strategy is determined by the amount of routing information carried in each routing message.

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It is well known that the ability to support predictable interprocess communication is of great significance to computer-integrated manufacturing and process control systems. In this paper, we propose a strategy for an industrial standard, the SP-50 FieldBus, to support both intracell and intercell realtime communications. We first describe our strategy in detail and show that it is compatible with the current FieldBus draft standard. Under our strategy, the capacity of each link is divided into two parts. The first part is managed by the local link active scheduler (LAS) for intracell (intralink) communication. The second part is managed by a proposed global network manager for intercell (interlink) communication. By dividing the link capacity in this way, our strategy allows for fast local intracell connection establishment, while supporting global intercell connections. Using two examples, one for typical manufacturing systems and the other for multimedia networking, we also demonstrate the power and utility of the proposed strategy as compared to token-passing protocols.

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