Networks used in mission-critical applications must be highly fault-tolerant. The authors propose an FDDI-based reconfigurable network (FBRN) that can survive multiple faults. An FBRN consists of multiple FDDI trunk rings and has the ability to reconfigure itself in the face of extensive damage. They consider three classes of FBRNs depending on their degree of reconfigurability: N-FBRN (nonreconfigurable), P-FBRN (partially reconfigurable) and F-FBRN (fully reconfigurable). They analyze the performance of FBRNs in terms of their available bandwidth in the presence of faults. In mission-critical systems, it is not enough to ensure that the network is connected in spite of faults; the traffic carrying capacity of the network must be sufficient to guarantee the required quality of service. They present a probabilistic analysis of the available bandwidth of FBRNs given the number of faults. They find that a fully reconfigurable FBRN can provide a high available bandwidth even in the presence of a large number of faults. A partially reconfigurable FBRN is found to be an excellent compromise between high reliability and ease of implementation.>

We study the problem of guaranteeing synchronous message deadlines in token ring networks where the timed token medium access control protocol is employed. 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 capacities must be properly allocated to individual nodes. We address the issue of appropriate allocation of the synchronous capacities. Several synchronous bandwidth allocation schemes are analyzed in terms of their ability to satisfy deadline constraints of synchronous messages. We show that an inappropriate allocation of the synchronous capacities could cause message deadlines to be missed, even if the synchronous traffic is extremely low. We propose a scheme, called the normalized proportional allocation scheme, which can guarantee the synchronous message deadlines for synchronous traffic of up to 33% of available utilization.>

The problem of guaranteeing synchronous message deadlines in communication networks using the timed token medium access control protocol is studied. To ensure the transmission of synchronous messages before their deadlines, synchronous capacities must be properly allocated to individual nodes. A class of local synchronous capacity allocation schemes, which allocate the synchronous capacity to a node without using information about messages on the other nodes, is developed, analyzed, and evaluated in terms of the ability of the schemes to guarantee message deadlines. It is shown that one of the local allocation schemes proposed can achieve the same performance as that of the best global allocation scheme known to date.>

The problem of guaranteeing synchronous message deadlines in token ring networks in which the timed token medium access control protocol is used is discussed. Synchronous capacity, 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 capacities must be properly allocated to individual nodes. Several synchronous capacity allocation schemes are analyzed in terms of their ability to satisfy deadline constraints of synchronous messages. It is shown that an inappropriate allocation of the synchronous capacities could cause message deadlines to be missed, even if the synchronous traffic is extremely low. The normalized proportional allocation scheme, which can guarantee the synchronous message deadlines for synchronous traffic of up to 33% of available utilization is proposed.>

The authors study the problem of transmitting synchronous messages before their deadlines in communication networks where the timed token medium access control protocol is employed. Synchronous capacity, defined as the maximum time for which a node can transmit its synchronous message 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 capacities must be property allocated to individual nodes. The authors develop and analyze an optimal synchronous capacity allocation scheme. An optimal scheme can allocate the synchronous capacities in such a way that the synchronous message deadlines are guaranteed if there exists any allocation scheme that can do so. The optimality of the allocation scheme proposed here is formally proved, and the bounds for its worst case achievable utilization are derived.>