Mobile Service Clouds: A self-managing infrastructure for autonomic mobile computing services

Abstract. We recently introduced Service Clouds, a distributed infrastructure designed to facilitate rapid prototyping and deployment of autonomic communication services. In this paper, we propose a model that extends Service Clouds to the wireless edge of the Internet. This model, called Mobile Service Clouds, enables dynamic instantiation, composition, configuration, and reconfiguration of services on an overlay network to support mobile computing. We have implemented a prototype of this model and applied it to the problem of dynamically instantiating and migrating proxy services for mobile hosts. We conducted a case study involving data streaming across a combination of PlanetLab nodes, local proxies, and wireless hosts. Results are presented demonstrating the effectiveness of the prototype in establishing new proxies and migrating their functionality in response to node failures.

BU/NSF Workshop on Internet Measurement, Instrumentation and Characterization

OBJECTIVES AND OVERVIEW Because of its growth in size, scope, and complexity--as well as its increasingly central role in society--the Internet has become an important object of study and evaluation. Many significant innovations in the networking community in recent years have been directed at obtaining a more accurate understanding of the fundamental behavior of the complex system that is the Internet. These innovations have come in the form of better models of components of the system, better tools which enable us to measure the performance of the system more accurately, and new techniques coupled with performance evaluation which have delivered better system utilization. The continued development and improvement of our understanding of the properties of the Internet is essential to guide designers of hardware, protocols, and applications for the next decade of Internet growth. As a research community, an important next step involves an comprehensive look at the challenges that lie ahead in this area. This includes an an evaluation of both the current unsolved challenges and the upcoming challenges the Internet will present us with in the near future, and a discussion of the promising new techniques that innovators in the field are currently developing. To this end, the Web and InterNetworking Research Group at Boston University (WING@BU), with support from the National Science Foundation, (grant #9985484) organized a one-day workshop which was held at Boston University on Monday, August 30, 1999 (immediately preceding ACM SIGCOMM '99).National Science Foundation (9985484

RTZen: Highly Predictable, Real-Time Java Middleware for Distributed and Embedded Systems

Distributed real-time and embedded (DRE) applications possess stringent quality of service (QoS) requirements, such as predictability, latency, and throughput constraints. Real-Time CORBA, an open middleware standard, allows DRE applications to allocate, schedule, and control resources to ensure predictable end-to-end QoS. The Real-Time Specification for Java (RTSJ) has been developed to provide extensions to Java so that it can be used for real-time systems, in order to bring Java's advantages, such as portability and ease of use, to real-time applications.In this paper, we describe RTZen, an implementation of a Real-Time CORBA Object Request Broker (ORB), designed to comply with the restrictions imposed by RTSJ. RTZen is designed to eliminate the unpredictability caused by garbage collection and improper support for thread scheduling through the use of appropriate data structures, threading models, and memory scopes. RTZen's architecture is also designed to hide the complexities of RTSJ related to distributed programming from the application developer. Empirical results show that RTZen is highly predictable and has acceptable performance. RTZen therefore demonstrates that Real-Time CORBA middleware implemented in real-time Java can meet stringent QoS requirements of DRE applications, while supporting safer, easier, cheaper, and faster development in real-time Java

Evaluation of global rainfall products for runoff simulation in the Narayani Basin, Nepal using SWAT

The availability of global precipitation datasets with different spatial and temporal resolutions has made hydrological simulation easier in catchments with no or sparse rain-gauge networks. However, the performance of these datasets is not consistent over different regions. Therefore, an evaluation of global precipitation products is necessary to check which one of them represents correctly the precipitation in a particular region. This study evaluates TRMM, APHRODITE, CHIRPS, PERSIANN-CDR and CFSR precipitation products in the Narayani River basin, Nepal. These precipitation datasets were compared with the observed precipitation. Next, the datasets were evaluated on the basis of runoff simulation. For each dataset, SWAT hydrological model was run and the simulated runoff was compared with observed runoff at four gauging stations in the Narayani, Kaligandaki, Trishuli and Budhigandaki rivers. The model performance was evaluated using the indices R2, NSE and PBIAS. The result for the comparison of precipitation datasets with observed precipitation showed that these datasets are good enough to represent the inter-annual (monthly and seasonal) variability in the precipitation. However, these datasets have varied biases with the observed precipitation. Although, APHRODITE performed best in representing the precipitation variability, it showed larger bias than TRMM and CHIRPS. The datasets performed good in representing runoff variability in all four basins with CFSR showing the least correlation with observed runoff. However, TRMM and CHIRPS had small biases at Kaligandaki and Narayani basin while the remaining datasets showed large biases. Similarly for the Trishuli basin, all datasets performed unsatisfactorily with PBIAS higher than -25%. CFSR showed very good performance in terms of bias in Budhigandaki basin while remaining datasets showed larger bias. However, CFSR showed only satisfactory results while representing the variability. The result of this study showed that TRMM and CHIRPS are good enough for runoff prediction in ungauged basins for preliminary studies

Tools and Techniques for Performance Measurement of Large Distributed Multiagent Systems

Performance measurement of large distributed multiagent systems (MAS) offers challenges that must be addressed explicitly in the agent infrastructure. Performance data is widely distributed and voluminous, and poor data collection can impact the operation of the system itself. However, performance metrics are essential to internal system function, e.g., autonomous adaptation to dynamic environments, as well as to external assessment. In this paper we describe the tools, techniques, and results of performance characterization of the Cougaar distributed agent architecture. These techniques include infrastructure instrumentation, pluginbased instrumentation of agents, and dynamic control of metric collection. We introduce multiple redundant “channels ” for metric delivery, each serving separate quality of service requirements. We present our techniques for instrumenting the agent society, justify the metrics chosen, and describe the tools developed for collecting these metrics. We also present results from distributed agent societies comprising hundreds of agents. Categories and Subject Descriptor