The Internet has led to the creation of a digital society, where (almost) everything is connected and is accessible from anywhere. However, despite their widespread adoption, traditional IP networks are complex and very hard to manage. It is both difficult to configure the network according to predefined policies, and to reconfigure it to respond to faults, load, and changes. To make matters even more difficult, current networks are also vertically integrated: the control and data planes are bundled together. Software-defined networking (SDN) is an emerging paradigm that promises to change this state of affairs, by breaking vertical integration, separating the network's control logic from the underlying routers and switches, promoting (logical) centralization of network control, and introducing the ability to program the network. The separation of concerns, introduced between the definition of network policies, their implementation in switching hardware, and the forwarding of traffic, is key to the desired flexibility: by breaking the network control problem into tractable pieces, SDN makes it easier to create and introduce new abstractions in networking, simplifying network management and facilitating network evolution. In this paper, we present a comprehensive survey on SDN. We start by introducing the motivation for SDN, explain its main concepts and how it differs from traditional networking, its roots, and the standardization activities regarding this novel paradigm. Next, we present the key building blocks of an SDN infrastructure using a bottom-up, layered approach. We provide an in-depth analysis of the hardware infrastructure, southbound and northbound application programming interfaces (APIs), network virtualization layers, network operating systems (SDN controllers), network programming languages, and network applications. We also look at cross-layer problems such as debugging and troubleshooting. In an effort to anticipate the future evolution of this new paradigm, we discuss the main ongoing research efforts and challenges of SDN. In particular, we address the design of switches and control platforms—with a focus on aspects such as resiliency, scalability, performance, security, and dependability—as well as new opportunities for carrier transport networks and cloud providers. Last but not least, we analyze the position of SDN as a key enabler of a software-defined environment.

https://publications.uni.lu/bitstream/10993/20596/1/survey_on_SDN.pdf

Software-Defined Networking: A Comprehensive Survey

Software-Defined Networking (SDN) is an emerging paradigm that promises to change this state of affairs, by breaking vertical integration, separating the network's control logic from the underlying routers and switches, promoting (logical) centralization of network control, and introducing the ability to program the network. The separation of concerns introduced between the definition of network policies, their implementation in switching hardware, and the forwarding of traffic, is key to the desired flexibility: by breaking the network control problem into tractable pieces, SDN makes it easier to create and introduce new abstractions in networking, simplifying network management and facilitating network evolution. In this paper we present a comprehensive survey on SDN. We start by introducing the motivation for SDN, explain its main concepts and how it differs from traditional networking, its roots, and the standardization activities regarding this novel paradigm. Next, we present the key building blocks of an SDN infrastructure using a bottom-up, layered approach. We provide an in-depth analysis of the hardware infrastructure, southbound and northbound APIs, network virtualization layers, network operating systems (SDN controllers), network programming languages, and network applications. We also look at cross-layer problems such as debugging and troubleshooting. In an effort to anticipate the future evolution of this new paradigm, we discuss the main ongoing research efforts and challenges of SDN. In particular, we address the design of switches and control platforms -- with a focus on aspects such as resiliency, scalability, performance, security and dependability -- as well as new opportunities for carrier transport networks and cloud providers. Last but not least, we analyze the position of SDN as a key enabler of a software-defined environment.

System Identification I

In this Chapter, we imagine a decision maker (or a group of experts) trying to establish or examine fair procedures to combine opinions about alternatives related to different points of view.

Multiple criteria decision making

Cyberphysical systems (CPSs) are new class of engineered systems that offer close interaction between cyber and physical components. The field of CPS has been identified as a key area of research, and CPSs are expected to play a major role in the design and development of future systems. In this paper, we survey recent advancements made in the development and applications of CPSs. We classify the existing research work based on their characteristics and identify the future challenges. We also discuss the examples of prototypes of CPSs. The aim of this survey is to enable researchers and system designers to get insights into the working and applications of CPSs and motivate them to propose novel solutions for making wide-scale adoption of CPS a tangible reality.

Design Techniques and Applications of Cyberphysical Systems: A Survey

In a cloud computing environment, resources are shared among different clients. Intelligently managing and allocating resources among various clients is important for system providers, whose business model relies on managing the infrastructure resources in a cost-effective manner while satisfying the client service level agreements (SLAs). In this paper, we address the issue of how to intelligently manage the resources in a shared cloud database system and present SmartSLA, a cost-aware resource management system. SmartSLA consists of two main components: the system modeling module and the resource allocation decision module. The system modeling module uses machine learning techniques to learn a model that describes the potential profit margins for each client under different resource allocations. Based on the learned model, the resource allocation decision module dynamically adjusts the resource allocations in order to achieve the optimum profits. We evaluate SmartSLA by using the TPC-W benchmark with workload characteristics derived from real-life systems. The performance results indicate that SmartSLA can successfully compute predictive models under different hardware resource allocations, such as CPU and memory, as well as database specific resources, such as the number of replicas in the database systems. The experimental results also show that SmartSLA can provide intelligent service differentiation according to factors such as variable workloads, SLA levels, resource costs, and deliver improved profit margins.

Intelligent management of virtualized resources for database systems in cloud environment

Business process execution language for Web services (BPEL) is becoming the industrial standard for modeling Web-service-based business processes. Behavioral compatibility for Web service composition is one of the most important topics. The commonly used reachability exploration method focuses on verifying deadlock freeness. When this property is violated, the states and traces in the reachability graph only give clues to redesign the composition. The redesign must then repeat itself until no deadlock is found. In this paper, multiple Web service interaction is modeled with a Petri net called composition net (C-net for short). The problem of behavioral compatibility among Web services is hence transformed into the deadlock structure problem of a C-net. If services are incompatible, a policy based on appending additional information channels is proposed. It is proved that the policy can offer a good solution that can be mapped back into the BPEL models automatically.

A Petri Net Approach to Analysis and Composition of Web Services

With the development of enterprise-wide and cross-enterprise application integration and interoperation toward Web service, Web service providers try to not only fulfill the functional requirements of Web service users but also satisfy their nonfunctional conditions in order to survive in the competitive market. A hot research topic is how to configure Web services to meet their demand when the diversity of user requirements, distinction of service components' performance, and limitation of resources are considered. This paper builds a Web service configuration net based on Petri nets in order to exhibit Web service configurations in a formal way. Then, an optimal algorithm is presented to help choose the best configuration with the highest quality of service to meet users' nonfunctional requirements. Finally, the simulation results and related analysis prove the soundness and correctness of our model and algorithm.

QoS-Aware Web Service Configuration

The system overload is a common problem in a Database-as-a-Serice (DaaS) environment because of unpredictable and bursty workloads from various clients. Due to the service delivery nature of DaaS, such system overload usually has direct economic impact on the service provider, who has to pay penalties if the system performance does not meet clients' service level agreements (SLAs). In this paper, we investigate techniques that prevent system overload by using admission control. We propose a profit-oriented admission control framework, called ActiveSLA, for DaaS providers. ActiveSLA is an end-to-end framework that consists of two components. First, a prediction module estimates the probability for a new query to finish the execution before its deadline. Second, based on the predicted probability, a decision module determines whether or not to admit the given query into the database system. The decision is made with the profit optimization objective, where the expected profit is derived from the service level agreements between a service provider and its clients. We present extensive real system experiments with standard database benchmarks, under different traffic patterns, DBMS settings, and SLAs. The results demonstrate that ActiveSLA is able to make admission control decisions that are both more accurate and more profit-effective than several state-of-the-art methods.

ActiveSLA: a profit-oriented admission control framework for database-as-a-service providers

With the popularity of Internet technology, Web services are becoming the most promising paradigm for distributed computing. However, when a single Web service fails to meet service requestor's multiple function needs, web services need to be dynamically configured together to form a web service composition. Since there may be many configurations providing identical functionality with different quality-of-service (QoS), a choice needs to be made according to users' functional and nonfunctional requirements. In this paper, we formulate a Web service functional configuration problem by using Petri nets. The graph structure and algebraic properties of the model are analyzed in detail to show that a basis solution of a state-shift equation of the Petri net model corresponds to a realizable configuration process. This result is later used to formulate the multiple attribute QoS optimization problem to a linear programming problem. Finally, a case study is performed to show that the proposed analysis result can be effectively applied in practice.

Pengcheng Xiong

Papers

Intelligent management of virtualized resources for database systems in cloud environment

A Petri Net Approach to Analysis and Composition of Web Services

QoS-Aware Web Service Configuration

ActiveSLA: a profit-oriented admission control framework for database-as-a-service providers

Web Service Configuration Under Multiple Quality-of-Service Attributes