Balasubramanian Seshasayee

Implementing Diverse Messaging Models with Self-Managing Properties using IFLOW

Implementing self-management is hard, especially when building large scale distributed systems. Publish/subscribe middlewares, scientific visualization and collaboration tools and corporate operational information systems are examples of one class of systems, distributed information flow infrastructures, that could benefit from self management. This paper presents IFLOW, an autonomic middleware for implementing these different distributed systems in a self-managing way. IFLOW reduces different messaging models down to a common information flow abstraction, creates a self-managing implementation of that abstraction and then provides a substrate for building diverse information flow systems. We describe the design and implementation of IFLOW and describe case studies of implementing different messaging models as self-managing systems.

Dynamic data driven application simulation of surface transportation systems

A project concerned with applying Dynamic Data Driven Application Simulations (DDDAS) to monitor and manage surface transportation systems is described. Building upon activities such as the Vehicle-Infrastructure Integration initiative, a hierarchical DDDAS architecture is presented that includes coupled in-vehicle, roadside, and traffic management center simulations. The overall architecture is described as well as current work to implement and evaluate the effectiveness of this approach for a portion the Atlanta metropolitan area in the context of a hypothesized emergency evacuation scenario.

VMedia: enhanced multimedia services in virtualized systems

This paper presents the VMedia multimedia virtualization framework, for sharing media devices among multiple virtual machines (VMs). The framework provides logical media devices, exported via a well defined, higher level, multimedia access interface, to the applications and operating system running in a VM. By using semantically meaningful information, rather than low-level raw data, within the VMedia framework, efficient virtualization solutions can be created for physical devices shared by multiple VMs. Experimental results demonstrate that the base cost of virtual device access via VMedia is small compared to native physical device access, and in addition, that these costs scale well with an increasing number of guest VMs. Here, VMedias MediaGraph abstraction is a key contributor, since it also allows the framework to support dynamic restructuring, in order to adapt device accesses to changing requirements. Finally, VMedia permits platforms to offer new and enhanced logical device functionality at lower costs than those achievable with alternative solutions.

Mobile service overlays: reconfigurable middleware for MANETs

Distributed applications running on Mobile Adhoc NET- works (MANETs) can benefit from underlying middleware that provides services for self-management. Such services can address the dynamic conditions associated with a MANETs operational environment and changes in end user needs. This paper describes Mobile Service Overlays (MSOs), an overlay network-based decentralized middleware that provides basic support for online management, shown useful for services like online reconfiguration for managing energy consumption and failure resilience. Decentralization is achieved by partitioning the applications overlay network into smaller units termed chains, and implementing decentralized reconfigurations involving specific chains, triggered by monitoring events. The paper also presents the overheads of these services in a lightweight, non-Java implementation of MSOs targeted at an example MANET application in cooperative robotics.

Spirits : using virtualization and pervasiveness to manage mobile robot software systems

Management capabilities comprise a key component of any autonomous distributed system. In this work our focus is on mobile systems like teams of robots exploring and operating in some physical environment. Here, basic management goals are to adapt application behavior to prevent or mitigate reductions in the applications quality of service. This paper presents the spirits system-level mechanisms supporting (1) behavior persistence – the ability to maintain some desirable behavior learned through online adaptation – and (2) behavior propagation – the ability to propagate a learned behavior across different physical components. With spirits, software management is enriched with a low-level mechanism, termed a spirit cache, which permits a mobile entity to cache its current state and code to realize behavior persistence. Next, a cached spirit can be acquired by a different physical component and then used, thereby propagating it. By using system-level virtualization techniques to realize spirit caching and propagation, both can be performed without the need to make any changes to application code, without requiring middleware-level support, and without changes to operating system kernels or utilities. Furthermore, any number of spirits can exist in a robot with system-level isolation guarantees. Experimental results presented in this paper highlight the types of overheads for spirit exchanges experienced on typical next generation virtualizable embedded machines, and indicate optimizations to be considered in future research.

VStore: efficiently storing virtualized state across mobile devices

Mobile virtualization is a nascent technology the value of which lies in enforcing data protection, providing process isolation and simplifying application reuse across device platforms. In this paper, we present VStore, a flexible mechanism for storage management and content protection that exploits virtualization to modularize data access and sharing mechanisms into containers separate from those containing guest operating systems and applications. This can provide mobile devices with rich storage options, including local, remote, or peer to peer stores, without affecting guest operating systems, middleware, or applications, and it enables diverse content create-query-share semantics. Further, VStore can provide the means to support centralized content protection and access control to all resident applications, thereby enabling new content distribution or privacy preservation policies to be enforced transparently. We discuss initial VStore implementation results and conclude by outlining new opportunities and challenges for further research.

Ad Hoc Distributed Simulation of Surface Transportation Systems

Current research in applying the Dynamic Data Driven Application Systems (DDDAS) concept to monitor and manage surface transportation systems in day-to-day and emergency scenarios is described. This work is focused in four, tightly coupled areas. First, a novel approach to predicting future system states termed ad hoc distributed simulations has been developed and is under investigation. Second, on-line simulation models that can incorporate real-time data and perform rollback operations for optimistic ad hoc distributed simulations are being developed and configured with data corresponding to the Atlanta metropolitan area. Third, research in the analysis of real-time data is being used to define approaches for transportation system data collection that can drive distributed on-line simulations. Finally, research in data dissemination approaches is examining effective means to distribute information in mobile distributed systems to support the ad hoc distributed simulation concept.

Enabling semantic communications for virtual machines via iConnect

iConnect is an abstraction that encapsulates all of a virtual machines interactions with outside entities. Its intent is to exploit semantic information to better support the end-to-end requirements of such VM communications. Focusing on the I/O performed by VMs and leveraging the fact that modern systems already have to virtualize the physical devices used by VMs, this paper shows that the iConnect abstraction can be implemented with the extension of existing virtual device interfaces. Specifically, by devising enhanced virtual devices, we can (1) efficiently implement the communication paths between virtual machines (VMs) and the virtualized platforms (VPs) on which they run, and (2) capture semantic information about VM-device interactions, which can then be used to implement additional functionality and efficient sharing of physical devices. The paper presents three concrete realizations of the iConnect abstraction: a multimedia device virtualization solution (VMedia) which utilizes semantic information to implement efficient sharing and enhanced functionality, a network virtualization solution that provides virtual NICs with QoS-support where the VM communicates its QoS requirements to the VP, and a storage virtualization solution which permits a VM to access a block device regardless of whether such a device is physically located locally or must be accessed at a remote location. A Xen-based implementation of the iConnect concept demonstrates substantial performance improvements and additional functionality derived from their use at a minimal cost to VMs, in part because iConnect utilizes additional computational resources of the VP and can take better advantage of certain underlying platform capabilities.

Combining compiler and operating system support for energy efficient I/O on embedded platforms

Mobile and embedded platforms have experienced dramatic advances in capabilities, largely due to the development of associated peripheral devices for storage and communication. The incorporation of these I/O devices has increased the overall power envelope of these platforms. In fact, system-level power consumption of mobile platforms is often dominated by peripheral devices. Since battery technologies alone have been unable to provide the lifetimes required by many platforms, in order to conserve energy, most devices provide the ability to transition into low power states during idle periods. The resulting energy savings are heavily dependent upon the lengths and number of idle periods experienced by a device. This paper presents an infrastructure designed to take advantage of device low power states by increasing the burstiness of device accesses and idle periods to provide a reduced power profile, and thereby an improvement in battery life. Our approach combines compiler-based source modifications with operating system support to implement a dynamic solution for enhanced energy consumption. We evaluate our infrastructure on an XScale-based embedded platform with a Linux implementation.

On the Resilience of Ad Hoc Distributed Simulation of Surface Transportation Systems with Unreliable Communications

The Dynamic Data Driven Application Systems (DDDAS) concept is examined in the context of monitoring and managing surface transportation systems in day-to-day and emergency scenarios. An approach to predicting future system states termed ad hoc distributed simulations is described. This approach uses on-line distributed simulation models that can incorporate real-time data and utilizes rollback operations to update state predictions as new information becomes available. This paper focuses on examining the reliability of ad hoc distributed simulations in mobile computing environments, and specifically, assessing the accuracy of future state predictions in the face of unreliable communications.