Konstantin Shagin

Efficacy of techniques for responsiveness in a wide-area publish/subscribe system

As the multiplicity of organizational domains often span across nations, or even continents, the need for federated communications across domains becomes paramount. Consequently, messaging middleware has become critical towards enabling cross-domain, wide-area federations. Cross-domain federation has placed increased emphasis on the need for the messaging system to provide Quality of Service (QoS), particularly with respect to responsive delivery of messages. Responsiveness, or timely delivery of messages, is critical in real-world services, such as a smart utility grid system. This study explores the efficacy of providing responsiveness in wide-area publish/subscribe messaging by evaluating several key techniques for managing latency. Specifically, this paper evaluates the following techniques: proactive best-path routing, reactive QoS-aware routing, and multipath routing. We present Harmony, a QoS-aware publish/subscribe middleware system, that adapts these techniques in order to provide responsive and high availability messaging. This study seeks to provide an in-depth understanding of how different techniques to manage responsiveness affect the end-to-end performance under various network conditions.

Delay analysis of real-time data dissemination

The growing popularity of distributed real-time applications increases the demand for QoS-aware messaging systems. In the absence of transmission rate control, congestion may prevent a messaging system from meeting its timeliness requirements. In this paper, we develop an analytic model for congestion in data dissemination protocols and investigate the effect of transmission rate on message delivery latency. Unlike previous works, we take into account the processing overhead of receiver buffer overflow, which has a significant impact on the results. A simulation is used to obtain more insight into the problem and to study a number of additional effects ignored by the analytic model. The presented analysis can be incorporated into a transmission rate control logic, to enable it to rapidly converge to an optimal transmission rate.

Extrapolation-based and QoS-aware real-time communication in wireless mobile ad hoc networks

In mobile ad hoc networks (MANETs), it is increasingly important to devote attention to real-time and quality of service (QoS) issues. We present here a novel extrapolation-based and QoS-aware technology for providing soft real-time services in MANETs. The proposed technology combines elements of proactive and location-based techniques. Each node maintains a global view, which is periodically updated through state exchange among all the nodes. At any time, a node is able to extrapolate the location of a given node based on its velocity vector. Resource management, dynamic scheduling, velocity-based extrapolation, and multipath search techniques are employed to meet the realtime and QoS requirements despite network contention and frequent topology changes. We demonstrate this technology by presenting a real-time and QoS routing protocol. We evaluate the performance of the protocol and compare it to the performance of other well-known routing protocols.

Pulsar: a resource-control architecture for time-critical service-oriented applications

The complexity of real-time systems is growing extremely rapidly, as they move from isolated devices to multilevel networked systems. Traditional methodologies for developing and managing these systems are not scaling to meet the requirements of a new generation of distributed applications. While developers of complex real-time applications are looking to service-oriented architecture to address their needs for ease of development and flexibility of integration, current software infrastructures for service-oriented applications do not address the issue of predictable latency for the applications they host. In this paper, we present Pulsar, a resource-control architecture for managing the end-to-end latency of a set of distributed, time-critical applications. The primary entity of Pulsar is called a controller, which regulates an aspect of resource allocation or scheduling policy. Controllers utilize policy configurations, which may include latency targets to be achieved or resource allocations to be honored, and interact with resource allocators and schedulers (e.g., thread schedulers, memory allocators, or bandwidth reservation mechanisms) to effect local policy. Controllers also provide feedback on how well they are executing a policy. Pulsar includes an application model which captures resource-sensitive behavior and requirements and is independent of high-level programming models and application programming interfaces.

A bandwidth management approach for quality of service support in mobile ad hoc networks

Bandwidth management is a key feature for providing quality of service (QoS) in contemporary mobile ad hoc networks (MANETs). In this paper, we present a novel approach to bandwidth reservation which is designed for highly mobile environments. In this scheme, a node takes into account the bandwidth requirements of its 2-hop neighbors. The design of this scheme does not depend on any routing protocol. We evaluate the proposed approach by incorporating it in the well known AODV protocol. The comparison between the original AODV and its extended version, with our approach, shows that the latter achieves a significantly lower latency and higher reliability.

A screen-oriented representation for mobile applications

Program analysis plays an important role in a variety of software engineering processes, such as automated code refactoring, compiler optimizations, and program slicing. The internal program representation used by the program analysis algorithm affects the power and efficiency of the analysis. In particular, representations that contain data-flow information alongside control flow are known to be especially useful. While there are many popular internal program representations with data-flow information for traditional languages and platforms, few specifically target mobile applications. In this paper, we propose a new data-flow-enabled representation that addresses the screen-oriented nature of a mobile application and explores its potential. We consider a mobile application to be a reactive system whose states are the screens, and whose events are user actions, incoming communication, or anything else that causes transition from one screen to another. The resulting representation is a finite state machine extended with data-flow information. We suggest that this representation can greatly contribute to optimization, refactoring, and understanding of mobile applications.