1,721,310 research outputs found
Experiences monitoring and managing QoS using SDN on testbeds supporting different innovation stages
No full textIn recent years there has been a big increase in the number of network-related experiments using software defined networking (SDN) technology. We report on our practical experience over 2 years running network experiments on three classes of testbed facility, each supporting researchers working at a different innovation stage. We run experiments using the commercial Amazon EC2 cloud facility, pre-commercial federated testbed of FIWARE Lab instances and the OFELIA experimental facility. We run an idealized common network experiment on each testbed, reducing its scope where needed to match testbed capabilities, and report details of the practical experience gained using a set of qualitative metrics for direct comparison across classes of testbed. We conclude with a concrete recommendation for pre-commercial testbed facilities to allow better support for network experiments in the future
Scalable classification of QoS for real-time interactive applications from IP traffic measurements
No full textMeasurement of network Quality of Service (QoS) has attracted considerable research effort over the last two decades. The recent trend towards Internet Service Providers (ISP's) offering application-specific QoS is creating possibilities for more sophisticated QoS metrics to be offered by ISP's in service level agreements. This in turn could be used for the purposes of improved network optimization and billing according to application specific QoS guarantees. We report a scalable near real-time approach using passively logging IP traffic data for classification of application latency and packet loss across a range of real-time interactive applications. We run six experiments involving Minecraft, Quake 3 Urban Terror, VLC video streaming and the commercial Wirofon VOIP application. We use a mixture of laboratory and real-world deployments, with run times ranging from hours to days, and observe a combination of real and simulated ISP latency and packet loss events. Our binary classification (i.e. classes 'OK' or 'lag') 10-fold cross validation F1 scores are between 0.80 and 0.93 depending on application type. Our multi-class classification (i.e. classes representing discrete packet loss or latency ranges) 10-fold cross validation F1 scores for Minecraft are 0.89 for latency and 0.90 for packet loss. With new business models between ISP's and application developers being actively considered this work represents a significant contribution to the debate by providing scientific evidence relating to a novel approach to scalable QoS measuremen
Methods for Enabling Recovery Actions in Ws-BPEL
No full textSelf-Healing is an emerging exigency for Information Systems where processes are everyday more complicated and where many autonomous actors are involved. Roughly, self-healing mechanisms can be viewed as a set of automatic recovery actions fired at run-time according to the detected fault. These actions can be at infrastructure level, i.e. transparently to the process, or they can be defined in the workflow model and executed by the workflow engine. In the Service Oriented Computing world Ws-BPEL is the most used language for web-service orchestration, but standard recovery mechanisms provided by Ws-BPEL are not enough to implement, with reasonable effort, lots of suitable recovery actions.This paper presents an approach where a designer defines a Ws-BPEL process annotated with some information about recovery actions and then a preprocessing phase, starting from this “annotated”Ws-BPEL, generates a “standard” Ws-BPEL, that is a file understandable for a standard Ws-BPEL engine. This approach has the advantage of avoiding any change in the engine using the standard capabilities to define specific behaviors that will realize recovery actions, but at the end are still a set of Ws-BPEL basic and structured activities
Challenges in designing of cooperative mobile information systems for the risk map of Italian cultural heritage
No full textItalian cultural heritage is one of the most famous in the world, but unfortunately is under risk of destruction. The Italian government has started a project to define the risk map of Italian cultural heritage (MARIS). Starting from this real example, we describe an example of a cooperative and mobile information system devoted to acquiring data about cultural heritage in an electronic way through a set of cooperative processes. In this paper, we show features of such an information system and critically analyze the main challenges that both information system and middleware designers have to face. Moreover, we present an attempt to characterize the elaboration capability of devices of an information system, by means of a dynamic definition, with the goal to evaluate which processes can be hosted in devices within a distributed and mobile environment
Reflective Architectures for Adaptive Information Systems
No full textNowadays the anytime/anywhere/anyone paradigm is becoming very important and new applications are being developed in many contexts. The possibility of using applications along a wide range of devices, networks, and protocols raises new problems related to delivery of services. Current academic and industrial solutions try to adapt services to the specific distribution channel, mainly by changing the presentation of the service. In this paper, we reverse this perspective by using adaptive strategies to try to adapt the delivery channel to services as well. We present a possible architecture and focus our attention on the use of reflective components in the adaptive process. Using the reflection principle, we are able to evaluate the channel constraints and the conditions in which the distribution channel is working at a specific time. This information, built with service, user, and context constraints, is used as input to adaptive strategies to change the current channel characteristics, to new ones satisfying all the requirements. If this kind of adaptation is not possible, we consider the different QoS levels offered by the service and the user’s readiness to accept a downgraded service provisioning
Partitioning rules for orchestrating mobile information systems
No full textNew mobile technologies such as Bluetooth or Wi-Fi suffer from many limitations and problems, especially when they are used in combination, whereas they are quite stable in small networks. The lack of specialised mobile middleware requires new methods in the design and execution of mobile information systems. We propose a two-phase approach to manage a mobile business process by partitioning a given workflow into several workflows, with each one governed by a controller. In the first phase, we introduce synchronisation tasks between different controllers. In the second phase, we create for each controller a local process view. Thanks to added tasks, the overall execution of all local workflows achieve the same result as the original one. The mobile scenario and the necessity for more automation lead us to choose the Business Process Execution Language for Web Services (BPEL4WS) as the language for the process definition
Workflow Management in Mobile Environments
No full textThe young mobile technologies, i.e Bluetooth or Wi-Fi, suffer of limitations and problems especially if the net is composed by many nodes. This trouble aspect affect also the design of Mobile Information System based on wireless networks. Our research focuses on the management of a business process in a mobile environment. This paper is about an approach to divide an unique workflow in different autonomous workflows each one controlled by a different actor. This fact allows the actors independence and the net partitioning limiting the number of hosts working in each subnet. The presented delegation model supports disconnected characteristics and the independent execution of the workflow parts that means the hosting of an independent engine in each controller. The mobile scenario and the necessity of the more automation lead us to choose BPEL4WS as language for the process definitio
SH-BPEL - A Self-Healing plug-in for Ws-BPEL engines
No full textSelf-Healing is an emerging exigence for Information Systems where processes are more and more complicated and where many autonomous actors are involved. Self-healing mechanisms can be viewed as a set of automatic recovery actions fired at run-time according to the detected fault. These actions can be at infrastructure level (i.e., transparentl to the process), or they can be defined in the workflow model and executed by the workflow engine. Standard recovery mechanisms provided by Ws-BPEL are not enough to implement with reasonable effort lots of suitable recovery actions. The aim of this paper is to present a Self-Healing plug-in for a Ws-BPEL engine that enhances the ability of a standard engine to provide process-based recovery actions
Distributed BPEL Processes
No full textBPEL only supports a strictly centralized and coordinated execution of Web service compositions, but this solution is clearly not the best option in many concrete cases. The conceptually monolithic BPEL process should be executed in a distributed setting, where each peer is only responsible for a fraction of the whole process and for the coordination with the other fragments. These considerations lead us to propose a formal approach to support the distributed execution of BPEL processes. The partitioning is customizable and easily intertwines with the adoption of special-purpose middleware infrastructures. In particular, the paper shows how we pair the distributed execution with a tuple-based infrastructure, to support distributed execution in mobile contexts, and with a publish and subscribe middleware, to support dynamically changing scenarios. Copyright © (2007) by Knowledge Systems Institute (KSI)
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