Arun Adiththan

Autonomic Management of Replica Voting based Data Collection Systems in Malicious Environments

We describe a model-based approach to QoS management in a replica voting based data collection system. The voting among replicated data collection devices achieves trusted data delivery to the end-user in a hostile environment: such as data corruptions by malicious devices and security & bandwidth attacks on the wireless data paths. How often an accurate data is delivered to the user in a timely manner depicts the QoS of data collection system. Aided by a computational model of the voting system, a situational assessment module macroscopically controls the voting system core based on the sensed external events. Our goal is the optimal use of system resources while enforcing an acceptable QoS. The paper describes the management methods for autonomic control of the degree of device replication and/or the algorithmic parameters (e.g., wireless bandwidth allocation) in response to the dynamically changing QoS needs and environment conditions. Our management methods are reusable across different systems, which lowers the software costs in the development of such complex systems.

Specification of Transactional Requirements for Web Services using Recoverability

In Service-Oriented Computing SOC, a business transaction comprises of several web services provided by multiple enterprises. The transactional behaviour of individual web services must be considered for service selection so that the composition of web services results in a reliable execution. It is difficult for a business analyst to envisage the desired business policies of a process in terms of transactional properties of the corresponding service. Hence, an abstract mechanism that enables the business analyst to specify the transactional properties in a simple manner must be introduced. Towards this objective, it is proposed to express the transactional properties in terms of the recoverability of services. The transactional web services are grouped into different levels of recoverability based on their recovery cost. The estimated recovery costs are empirically verified and validated.

QoS-Oriented Management of Automobile Cruise Control Processes

Networked embedded software systems incorporate varying degrees of adaptation behavior to sustain their operations with acceptable quality of service (QoS), in the face of hostile external events. For instance, a highly agile cruise control system of a car may dynamically adjust its controller parameters to generate a higher-than-normal increase in torque when encountering a higher road elevation (relative to a normal controller). The paper formulates model-based assessment techniques to reason about how capable is a networked system in meeting its QoS specs in the presence of hostile external events. As a case study, we describe the QoS assessment of a multi-vehicle adaptive cruise control system.

Dynamic Transaction Aware Web Service Selection

Web service composition, that recursively constructs a composite web service out of the existing services based on a business workflow has been acknowledged as a promising approach to meet the user...

Service Abstractions With Fault Virtualization for Distributed Network Infrastructures

The paper deals with service abstractions that allow managing the dependability features of networked application systems.Component-level faults in the infrastructure are mapped on to degradations in the service quality space. Fault recovery mechanisms in a service-layer algorithm, if any, purport to maintain either the same level of service as in the no-fault case or a reduced level of service proportionate to the fault severity. Treating the occurrence of component faults as a normal case rather than as an exception, a virtualization mechanism provides a systematic mapping of faults on to canonical service quality spaces in a measurable way (e.g.,service availability and agility). Our paper describes the generic mechanisms and programming interfaces in the virtualization layer to manage the infrastructure in a flexible way that allows attaining an optimal service quality. Such service layer abstractions are useful for applications to in fuse adaptive fault-tolerance and quality assurance.

Tx-policy: transactional policies for reliable web service composition

In Web services paradigm, whenever a single service cannot meet the requirements of a user, many services need to be composed that can collectively satisfy the user expectations. Existing research focuses on service selection based solely on non-functional properties for composition, whenever there is more than one service provider who is offering services with similar functionality. However, the transaction behavioral aspects of a service, which ensure the reliability of a composite service has not been considered till now. Currently, the transactional properties cannot be represented as a part of service definition. To address this need, it is proposed to specify transactional properties using WS-Policy language and integrate it with the service definition. The transactional requirements of service consumer are matched with transactional policies of service providers and the correct set of services is selected for composition that will result in reliable execution. This approach is experimented with a case study of Scan Report Generation process in health care domain.

Management of QoS-oriented Adaptation in Automobile Cruise Control Systems

A quantitative assessment of the QoS (quality of service) capability of an embedded software system S enables a sustained QoS behavior and/or reduced cost of system operations, in the face of uncontrolled external environment conditions incident on S[1]. In this paper, we study the autonomic management of adaptive cruise control (ACC) processes in automobiles based on a model-based system assessment logic.

Assessment of QoS adaptation and cyber-defense mechanisms in networked systems

The paper describes methods to evaluate the QoS capability of a networked system S operating under hostile environment conditions. We evaluate the run-time compliance of system S with the QoS prescription of applications in terms of non-functional attributes that capture the QoS behavior of S (e.g., transaction latency & drop rate in an on-line web service). We benchmark the QoS capability of S by exercising stress-tests on a simulation model of S with artificially injected environment conditions. Our model-based system assessment methods are anchored on PO-MDP frameworks that are currently advocated for network reliability and performance analysis. As case study, we describe the assessment of a CDN (content distribution network) vis-a-vis the content read latency and overhead experienced by clients. Our CDN assessment employs models of the internal algorithmic processes that strive to optimally place the content caching nodes in a distribution topology.

Benchmarks to compare cloud service providers for seamless customer migration

The paper advocates a seamless cloud abstraction to enable the mobility of clients: i.e., a cloud that appears to offer the same service-level properties despite the heterogeneous nature and geographic location of the cloud providers. The paper concretely defines the service attributes experienced by a client application: such as availability, elasticity, resilience, and mobility, in terms of the cloud infrastructure parameters (i.e., VM instances and network bandwidth). Since the IaaS parameters are hard to measure directly, we map the client-visible SaaS-layer attributes onto the IaaS parameters of the CSP. The paper describes SaaS layer measurements of an image data service on the PlanetLab, as an instance of seamless cloud.

Verifying QoS properties of trusted data sensing

Voting among replicated data collection devices achieves trusted data delivery to the end-user in a hostile environment. Failures may occur during data collection process: such as data corruptions by malicious devices and security/bandwidth attacks on data paths. How often a correct data is delivered to the user in a timely manner depicts the voting QoS. We study a model-based approach to inject faults in a data collection system for verification purposes. We advocate a stress-test of the system, i.e., subjecting the system to harsh conditions, to assess its resilience. The paper provides experimental studies of a voting system under injected faults, with message & time complexity analysis.