We propose multi-class signaling overload control algorithms, for telecommunication switches, that are robust against different input traffic patterns and system upgrades. In order to appropriately measure the system load when several classes of signaling traffic are present, we first introduce the concept of equivalent system load measure that converts the multiple system measures associated with different classes of traffic into a single measure with respect to a pre-defined base class. We use this measure to develop three multi-class overload detection and measurement algorithms. Next, we develop a new algorithm for partitioning the allowable equivalent system load across multiple traffic classes, using a strict priority scheme. Using simulations of call flows from mobile telecommunications standards, we compare different multi-class overload algorithms under a variety of overload conditions. Our simulation results indicate that our algorithm that measures system load using a combination of request acceptance rate and processor occupancy provides highly reactive and robust overload control. Last, for the purpose of making the overload control algorithms more robust, we propose a measurement-based simple regression technique to dynamically estimate key system parameters. We find that estimates derived in this manner converge rapidly to their true values.

Telecommunication switches implement overload controls to maintain call throughput and delay at acceptable levels during periods of high load. Existing work has mostly focused on controls under sustained overload-they do not meet the demands of modern telecommunication systems where the increased number of services and mobile subscribers often creates fast changing hot spots. We introduce new algorithms that are designed to be highly reactive to sudden bursts of load. One algorithm is a modified version of RED for signaling traffic that measures the queue size. The second algorithm uses two measures: call acceptance rate and processor occupancy. Using simulations of realistic system models, we compare these new algorithms with each other and an existing algorithm that uses processor occupancy only. Our simulation results and qualitative arguments show that the combination of acceptance rate and processor occupancy results in a highly reactive and robust signaling overload control.

Parallel computing on local area networks is generally based on mechanisms that specifically target the properties of the local area network environment. However, these mechanisms do not effectively extend to wide area networks due to issues such as heterogeneity, security, and administrative boundaries. We present a system which enables application programmers to write parallel programs in Java and allows Java-capable browsers to execute parallel tasks. It comprises a virtual machine model which isolates the program from the execution environment, and a runtime system realizing this virtual machine on the Web. Load balancing and fault masking are transparently provided by the runtime system.

Java, in combination with Web browsers' abilities to load and execute untrusted Java applets in a secure fashion, has made computing over the Web a possibility. Now the challenge is to fully utilize this potential, given the limitations imposed by browsers. This paper presents KnittingFactory, an infrastructure to facilitate Web-based computing, which addresses this challenge. It supports building distributed applications, specifically those consisting of Java applets executing in browsers. It is composed of: (i) a distributed name service to assist users in locating other participants of a distributed computation via standard browsers; (ii) an embedded class server to eliminate the need for external HTTP servers for serving applet code; and (iii) a technique for direct applet-to-applet communication. In this paper, we describe the design and implementation of KnittingFactory and demonstrate its benefits by applying it to three distinct areas of Web-based computing. First, we apply our distributed name service to a client/server architecture to enable RMI clients to locate servers on unknown hosts. Second, we use the embedded class server to extend the capability of Charlotte, a parallel computing environment. Finally, we build a collaborative application using our direct applet-to-applet communication technique which does not require a forwarding agent. © 1998 John Wiley & Sons, Ltd.