Nir Naaman

High throughput reliable message dissemination

We consider applications that require high rate, reliable message dissemination in a many-to-many environment. Examples of such applications include stock market centers and synchronized server clusters. As network capacity increases, the achievable throughput of messaging applications becomes bounded by processing times rather than communication speed. To reduce processing times we suggest the use of message aggregation. We consider performing message aggregation at either the sender, a message-server, or a network switch. The performance of each of these methods in terms of throughput and delay is analytically evaluated and compared against that of a naive implementation that does not perform message aggregation. We show that in typical real-world messaging applications, performing message aggregation can increase throughput by order of magnitude.We base our results on experiments that have been conducted using various operating systems running on different hardware platforms. Our results indicate that the achievable throughput of messaging applications is determined by the number of packets-per-second, rather than bytes-per-second, a receiver or a transmitter should handle.

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.

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 self-managed self-optimized publish-subscribe system

Publish/subscribe based communication systems have become very popular in recent years. Such systems are becoming larger and more complex, and thus require a smart management framework. An important challenge in this context is to efficiently disseminate the data flows sent from the publishers to the subscribers. To this aim, multicast dissemination is often used, requiring a smart mapping of data flows to multicast groups. Most existing publish/subscribe systems use static configuration and thus do not efficiently handle dynamic changes in the publish/subscribe system. In this work, we present a self-managed and self-optimized publish/subscribe system that efficiently adapts to changes in run time. A key element in the solution is a smart mapping algorithm that computes efficient routes for the data flows based on the current conditions in the system. The mapping algorithm takes into account various costs and constraints that are associated with the transition from one mapping to another during run time. The solution we present maintains the publish/subscribe system optimized while at the same time ensuring the stability of the system. We complement our work with a comprehensive simulation study in which we evaluate the suggested solution. The results clearly demonstrate the advantages of a dynamic self-optimized system over a static system.