International audience

Tools for automated deployment and management are often used in the cloud computing platforms. Since this technology is rapidly evolving, it is important to guarantee the reliability and the efficiency of these tools. The paper proposes a framework CMT-VSE for validation of configuration management tools and for providing tenant requests with timed recommendations for their safe execution. Such recommendations can be utilized to execute the chains of commands in an asynchronous mode. Experimental evaluation with Ansible-2.16 and SaltStack-3006 showcases the efficiency of CMT-VSE.

International audience

International audience

8 pages, as submitted to the 17th International Conference on Evaluation of Novel Approaches to Software Engineering

We present a novel formalism for describing the evolution of dynamic-link network parameters; it is based on the Cellular Automaton (CA) model. Such formalism is of wide-use for modeling natural (e.g., physical, chemical, etc.) processes. We propose a particular model and survey the related work, with respect to the use of CA to simulate various communication networks. We showcase the flexibility of the proposed approach to model different evolution patterns. These patterns can be used to emulate / simulate different network scenarios (states of the network parameters), and test novel implementations under distinct conditions. Additionally, we propose an algorithm for guaranteeing that the described patterns hold properties of interest, within a bounded time.

Homing sequence derivation for nondeterministic finite state machines (NFSMs) has important applications in software/hardware system testing and verification. Unlike prior methods based on explicit tree-based search, in this article we formulate the derivation of a preset/adaptive homing sequence in terms of quantified Boolean formula (QBF) solving. This formulation exploits compact circuit representation of NFSMs and QBF encoding of the existence condition of homing sequence for effective computation. The implicit circuit representation effectively avoids explicit state enumeration, and can be more scalable. Different encoding schemes and QBF solvers are evaluated for their suitability for the homing sequence derivation. Experiments on various computation methods and benchmarks show the generality and feasibility of a proposed approach.

Software Defined Networking (SDN) is a novel network management technology, which currently attracts a lot of attention due to the provided capabilities. Recently, different works have been devoted to testing / verifying the (correct) configurations of SDN data planes. In general, SDN forwarding devices (e.g., switches) route (steer) traffic according to the configured flow rules; the latter identifies the set of virtual paths implemented in the data plane. In this paper, we propose a novel preventive approach for verifying that no misconfigurations (e.g., infinite loops), can occur given the requested set of paths. We discuss why such verification is essential, namely, how, when synthesizing a set of data paths, other not requested and undesired data paths (including loops) may be unintentionally configured. Furthermore, we show that for some cases the requested set of paths cannot be implemented without adding such undesired behavior, i.e., only a superset of the requested set can be implemented. Correspondingly, we present a verification technique for detecting such issues of potential misconfigurations and estimate the complexity of the proposed method; its polynomial complexity highlights the applicability of the obtained results. Finally, we propose a technique for debugging and repairing a set of paths in such a way that the corrected set does not induce undesired paths into the data plane, if the latter is possible.

In this paper, a novel model-based approach to verify dynamic networks is proposed. The network topology and dynamic link parameters are described as a many sorted first order logic formula, that is verified by an SMT-solver (z3 in our case) with respect to a set of properties. The formula is also used for run-time network verification when a given static network instance is implemented. Preliminary experiments showcase the expressiveness and current limitations of the proposed approach.

The paper presents a work in progress on the Quality of Experience (QoE) assessment in the context of Software Defined Networking (SDN). Preliminary experimental results clearly demonstrate the necessity of considering QoE parameters, which are not taken into account in traditional networks. Dynamic network (re-) configuration requires monitoring and measuring attributes not only at the network level but also at the control and application planes. We discuss a list of such parameters and propose a monitoring algorithm to consider distributed and asynchronous points of observation for the QoE assessment of SDN network services. Further, for the cases when a low QoE level is detected (or predicted using machine learning), we propose an algorithm for effective diagnosis of the QoE degradation, based on an iterative deduction of a QoE attribute contributing the most to a low QoE value.

International audience

International audience

Abstract A top-down approach is presented for checking the existence and derivation of an adaptive distinguishing test case (called also an adaptive distinguishing sequence) for a nondeterministic finite state machine (NDFSM). When such a test case exists, the method returns a canonical test case that includes all other distinguishing tests of the given complete observable NDFSM. In the second part of the paper, a constructive approach is provided for deriving a class of complete observable NDFSMs with n states, n > 2, and 2 n − n − 1 inputs such that a shortest adaptive distinguishing test case for each NDFSM in the intended class has the length (height) 2 n − n − 1. In other words, we prove the reachability of the exponential upper bound on the length of a shortest adaptive distinguishing sequence for complete observable NDFSMs while for deterministic machines the upper bound is polynomial with respect to the number of states. For constructing the intended class of NDFSMs for a given n , we propose a special linear order over all the non-empty subsets without singletons of an n -element set. The obtained tight exponential upper bound initiates further research on identifying certain NDFSM classes where this upper bound is not reachable.

International audience

International audience

International audience

International audience

This paper is devoted to study the use of 'gedanken' experiments with Finite State Machines (FSMs) for protocol passive testing optimization. We discuss how the knowledge obtained from the state identification of an implementation under test (IUT) can be utilized for effective IUT monitoring. Differently from active testing techniques, such identification is performed by only observing the IUT behavior. If the state identification is possible (at least partially), then this fact allows to reduce the number of properties (test purposes) to be checked at certain execution point(s). Correspondingly, this allows to simplify and/or accelerate, i.e. improve the monitoring process by verifying the system behavior only at critical states against the appropriate set of properties associated with a given state. The paper discusses which 'gedanken' experiments can be considered for this purpose and how they can be derived for various specifications of communication protocols. The results presented in the paper are followed by an illustrative protocol example that demonstrates the efficiency of the proposed approach.

In this paper, we present a framework for evaluating the QoE of a service that includes functional and non-functional service requirements. Non-functional requirements are classified into objective, subjective, and business parameters that affect Quality of Service (QoS), Quality of Experience (QoE), and Quality of Business (QoBiz), correspondingly. As those metrics have a strong dependency between each other, we discuss how the QoE of a web-based Over-The-Top service (OTT) can be evaluated taking into account subjective, objective and business parameters. The functional service behavior is described by an Extended Finite State Machine (EFSM) in which non-functional objective, subjective and business-related parameters are tracked using context variables and corresponding updating functions. These parameters are used to evaluate the QoE of the service. We show that the corresponding model allows to keep a track of a user-service interaction. Moreover, the model of the service integrates subjective, objective and business parameters, and thus, can be applied to the QoE evaluation of any OTT service.

International audience

This paper presents a short survey on the quality evaluation of web services. The most popular metrics for estimating such quality and user perception of web services are Quality of Service (QoS) and Quality of Experience (QoE), which represent objective and subjective assessments correspondingly. For different types of web services, the values of QoS and QoE are measured in different ways. In this paper, we consider various definitions of QoS based on web service parameters and describe several methods for evaluating QoS and QoE. We start with experimental evaluation of QoS based on network traffic analysis and further turn to model based methods for QoS estimating. Existing relationships between different kinds of service quality evaluation are also discussed.