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 message belonging to the connection. 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 worst-case 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. Although the proposed solution starts with searching all possible routes in parallel, it prunes infeasible routes quickly, and its worst-case operational overhead is shown to be only a linear function of the number of links in the network. Several examples and simulation results are presented to demonstrate the effectiveness of the proposed distributed route selection scheme as compared to sequential route-search schemes.

Real-time communication with performance guarantees is expected to become an important and necessary feature of future computer networks. In this paper, we present a scheme which can provide real-time communication services with both absolute and statistical performance guarantees on multiaccess bus networks for given input traffic characteristics and performance requirements. The proposed scheme reserves network bandwidth for real-time connections according to their needs. It also allows for independent addition and deletion of real-time connections while preserving existing guarantees. Our extensive simulation results for motion video communication have shown the proposed scheme to outperform the other well-known schemes.

Given the client's traffic-generation characteristics and performance requirements, we propose a real-time communication scheme that provides delivery delay guarantees in a multiaccess local-area network (LAN). This scheme (i) reduces the link capacity that needs to be reserved to an average level as compared to the worst-case level required for deterministic performance guarantees, and (ii) preserves the ability of independent addition and deletion of real-time channels.

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 real-time 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 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.

To guarantee the delivery of real-time messages before their deadline, a real-time connection or channel 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 worst-case end-to-end delay over the selected route may not exceed the user-specified delay bound. We propose a table-driven distributed route-selection scheme that is guaranteed to find a "qualified" route, if any, that meets the performance requirement of the requested channel without compromising any of the existing guarantees. The proposed scheme uses the Bellman-Ford shortest path algorithm to build real-time delay tables, and hence, can solve the route-selection problem by a simple table look-up. Several examples 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). The authors develop distributed loop-free 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. 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, especially for sparse computer networks. The authors prove the correctness of the proposed strategy, and give several illustrative examples. The performance of this strategy is shown to be better than, or at least as good as, that of APRS and any multiorder routing strategies, in which the order of a routing strategy is determined by the amount of routing information carried in each routing message.>

A strategy for handling real-time communications under the FieldBus protocol, which provides end-to-end delivery delay guarantees for time-critical messages, is proposed. This strategy provides a fast local mechanism for establishing intraworkcell real-time connections, while supporting global interworkcell real-time connections. The proposed strategy is fully compatible with the current draft proposal of the FieldBus protocol and also provides flexibility for the choice of scheduling algorithms and adaptability for different traffic loads. Numerical examples are given based on a typical manufacturing network.>