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Several schemes for detecting faults at the processor level in a multiprocessor system have been discussed in the past. One such scheme (A. Dahbura et al., 1989) works by running secondary versions of jobs on the unused or spare processors of the system and uses the comparison approach (J. Maeng and M. Malek, 1981) to detect faults. We build upon this scheme and propose three new multiprocessor allocation strategies that run a variable number of versions per job. These schemes permit online detection and, in many cases, location of faulty processors in a system with nominal degradation in its delay/throughput performance; these delays are limited chiefly to the delays associated with job preemptions. Two new metrics, the fault detection capability (FDC) and the fault location capability (FLC), are introduced to evaluate these schemes. Extensive simulation results are performed to obtain performance figures for the various schemes. Stochastic Petri net models are also developed to obtain approximate performance results. The results show that these schemes utilize spare capacity more efficiently, thereby improving upon the fault detection and location capabilities of the system.>

The authors propose MaTPi, a new media-access protocol for the efficient utilization of resources in a local-area optical WDMA network. Most of the earlier work on reservation based media access protocols for single-hop optical networks has assumed the availability of state-of-the-art transmitters and/or receivers which are capable of tuning to the required wavelengths within nanoseconds. Their protocol operates in the region where the tuning times of the end-devices are of the same order of magnitude as the transmission time of a packet. In the basic MaTPi protocol, network throughput is improved by effectively overlapping the tuning duration of a transmitter in a node with the transmitting times of lasers in other nodes. They extend this basic protocol to the mult-MaTPi protocol, where each node has more than one transmitter to further improve the bandwidth efficiency of the network. Preliminary simulation results indicate that this practical protocol is indeed capable of achieving high throughput with low-cost, off-the-shelf components. A number of extensions to this protocol are also discussed.>

Three new decomposition methods are developed for the exact analysis of stochastic multi-facility blocking models of the product-form type. The first is a basic decomposition algorithm that reduces the analysis of blocking probabilities to that of two separate subsystems. The second is a generalized M-subsystem decomposition method. The third is a more elaborate and efficient incremental decomposition technique. All of the algorithms exploit the sparsity of locality that can be found in the demand matrix of a system. By reducing the analysis to that of a set of subsystems, the overall dimensionality of the problem is diminished and the computational requirements are reduced significantly. This enables the efficient computation of blocking probabilities in large systems. Several numerical examples are provided to illustrate the computational savings that can be realized.

A fast packet switching module for use in B-ISDN switching architectures is described. The module is built around a self-routing banyan network which employs dilations and replications to enhance throughput. The differing requirements of delay and loss sensitivity for various traffic types are handled by assigning priorities to packets. A new result in the form of the throughput equation of lower priority packets in a banyan network which is improved by dilation, replication and internal speed-up is presented. The delay versus throughput analysis shows that the switch module is capable of handling integrated voice-data-video traffic efficiently.>