Testing from a stochastic timed system with a fault model

In this paper we present a method for testing a system against a non-deterministic stochastic finite state machine. As usual, we assume that the functional behaviour of the system under test (SUT) is deterministic but we allow the timing to be non-deterministic. We extend the state counting method of deriving tests, adapting it to the presence of temporal requirements represented by means of random variables. The notion of conformance is introduced using an implementation relation considering temporal aspects and the limitations imposed by a black-box framework. We propose an algorithm for generating a test suite that determines the conformance of a deterministic SUT with respect to a non-deterministic specification. We show how previous work on testing from stochastic systems can be encoded into the framework presented in this paper as an instantiation of our parameterized implementation relation. In this setting, we use a notion of conformance up to a given confidence level

Extending stream X-machines to specify and test systems with timeouts

Stream X-machines are a kind of extended finite state machine used to specify real systems where communication between the components is modeled by using a shared memory.In this paper we introduce an extension of the Stream X-machines formalism in order to specify delays/timeouts.The time spent by a system waiting for the environment to react has the capability of affecting the set of available outputs of the system. So, a relation focusing on functional aspects must explicitly take into account the possible timeouts.We also propose a formal testing methodology allowing to systematically test a system with respect to a specification. Finally, we introduce a test derivation algorithm. Given a specification, the derived test suite is sound and complete, that is, a system under test successfully passes the test suite if and only if this system conforms to the specification

Using genetic algorithms to generate test sequences for complex timed systems

The generation of test data for state based specifications is a computationally expensive process. This problem is magnified if we consider that time con- straints have to be taken into account to govern the transitions of the studied system. The main goal of this paper is to introduce a complete methodology, sup- ported by tools, that addresses this issue by represent- ing the test data generation problem as an optimisa- tion problem. We use heuristics to generate test cases. In order to assess the suitability of our approach we consider two different case studies: a communication protocol and the scientific application BIPS3D. We give details concerning how the test case generation problem can be presented as a search problem and automated. Genetic algorithms (GAs) and random search are used to generate test data and evaluate the approach. GAs outperform random search and seem to scale well as the problem size increases. It is worth to mention that we use a very simple fitness function that can be eas- ily adapted to be used with other evolutionary search techniques

Testing timed systems modeled by stream X-machines

Stream X-machines have been used to specify real systems where complex data structures. They are a variety of extended finite state machine where a shared memory is used to represent communications between the components of systems. In this paper we introduce an extension of the Stream X-machines formalism in order to specify systems that present temporal requirements. We add time in two different ways. First, we consider that (output) actions take time to be performed. Second, our formalism allows to specify timeouts. Timeouts represent the time a system can wait for the environment to react without changing its internal state. Since timeous affect the set of available actions of the system, a relation focusing on the functional behavior of systems, that is, the actions that they can perform, must explicitly take into account the possible timeouts. In this paper we also propose a formal testing methodology allowing to systematically test a system with respect to a specification. Finally, we introduce a test derivation algorithm. Given a specification, the derived test suite is sound and complete, that is, a system under test successfully passes the test suite if and only if this system conforms to the specification

Efficient T-CONT-agnostic Bandwidth and Wavelength Allocation for NG-PON2

Dynamic bandwidth and wavelength allocation are used to demonstrate high quality of service (QoS) in time wavelength-division multiplexed–passive optical networks (TWDM-PONs). Both bandwidth and wavelength assignment are performed on the basis of transmission containers (T-CONTs) and therefore by means of upstream service priority traffic flows. Our medium access control (MAC) protocol therefore ensures consistency in processing alike classes of service across all optical network units (ONUs) in agreement with their QoS figures. For evaluation of the MAC protocol performance, a simulator has been implemented in OPNET featuring a 40 km, 40 Gbps TWDM-PON with four stacked wavelengths at 10 Gbps each and 256 ONUs. Simulation results have confirmed the efficiency of allocating bandwidth to each wavelength and the significant increase of network traffic flow due to adaptive polling from 9.04 to 9.74 Gbps. The benefit of T-CONT-centric allocation has also been measured with respect to packet delay and queue occupancy, achieving low packet delay across all T-CONTs. Therefore, improved NG-PON2 performance and greater efficiency are obtained in this first demonstration of T-CONTs allocated to both wavelength and time.Peer reviewe

Passive Testing with Asynchronous Communications and Timestamps

We develop a formal passive testing framework for software systems where parties communicate asynchronously. Monitors, placed in between the en- tities, check that a certain property holds over the observations of the interaction between users and the System Under Test (SUT). Due to the asynchronous nature of communications, the trace observed by the monitor might differ from the one produced by the SUT: the monitor observes inputs before they are received by the SUT and outputs are observed after they are sent by the SUT. It is neces- sary to take this into account in passive testing; otherwise we might obtain false positives or false negatives. In order to better assess the real causality between actions, we consider the case where each action is labelled with a timestamp giv- ing the time when it was observed at the monitor. We also assume that we know bounds on network latency and so the timestamps allow us to determine additional causalities between actions. Our monitors are implemented as automata that take into account communications being asynchronous. Our solution checks properties against traces in polynomial time and has low storage requirements. Therefore, our proposal is suitable for real-time passive testing.Research partially supported by the projects DArDOS (TIN2015-65845-C3-1-R (MINECO/FEDER)) and SICOMORo-CM (S2013/ICE-3006)

An extended framework for passive asynchronous testing

In passive testing a monitor observes the trace (sequence of inputs and outputs) of the system under test (SUT) and checks that this trace satisfies a given property $P$, potentially triggering a response if an incorrect behaviour is observed. Recent work has explored a variant of passive testing, in which we have a required property $P$ of the traces of the SUT and there is a first-in-first-out (FIFO) network between the SUT and the monitor. The problem here is that the trace observed by the monitor need not be that produced by the SUT. Previous work has shown how such asynchronous passive testing can be performed if the property $P$ is defined by a pair $(\rho,O_{\rho})$ that represents the requirement that if trace $\rho$ is produced by the SUT then the next output must be from the set $O_{\rho}$. This paper generalises the previous work to the case where the property $P$ is defined by a finite automaton

Bounded reordering in the distributed test architecture

In the distributed test architecture, the system under test (SUT) interacts with its environment at multiple physically distributed ports and the local testers at these ports do not synchronize their actions. This presents many challenges and, in particular, apparently incorrect behaviors can be the consequence of an erroneous assumption about the exact order in which actions were performed at different ports. In previous work, we defined a conformance relation for the distributed test architecture. Essentially, the SUT is faulty if we observe a trace σ such that no admissible reordering of the actions in σ could have been produced by the specification. However, this notion can be weak if the compared traces might be too different. This paper introduces conformance relations where, for a given metric, a reordering is only considered if the distance between the two traces is at most a certain bound k . We introduce two different metrics and provide algorithms to construct finite automata accepting these close , with respect to each metric, sequences. We also study the computational complexity of the two main problems associated with the new framework: deciding whether a trace is accepted by the new automaton and deciding whether one system conforms to a specification with respect to the new conformance relation

A tool supported methodology to passively test asynchronous systems with multiple users

Spanish MINECO/FEDER (grant number TIN2015-65845-C3-1-R); Region of Madrid (grant number S2013/ICE-3006)

NFV and SDN-based differentiated traffic treatment for residential networks

Producción CientíficaResidential networks play a critical role in assuring that services or applications such as tele-work, tele-education, medical care, entertainment, home automation, among others, have the required resources to obtain an optimal performance. Although current residential gateways try to meet the Quality of Service (QoS) demands, the traditional networking paradigm does not have the appropriate mechanisms to address the heterogeneous and dynamic nature of the services running at home. In this context, a feasible solution consists of leveraging the flexibility and adaptability of the Software Defined Networking (SDN) and Network Functions Virtualization (NFV) paradigms to provide a differentiated traffic treatment intended to improve the QoS support of residential networks. The proposal takes advantage of the Service Function Chaining (SFC) concept intrinsic to NFV as well as the capacity of an SDN-based residential gateway to differentiate the traffic of a certain application. Thus, an association between an SFC and the differentiated traffic is stablished to apply a specific treatment. Besides, a comprehensive architecture composed of the software defined residential network (SDRN), the software defined access network (SDOAN) and the NFV-compliant ISP's edge cloud infrastructure is envisioned. This architecture would allow dramatically improving the life cycle management of the residential network from a centralized point which follows a user-centric approach.Ministerio de Ciencia, Innovación y Universidades (grants TEC2015-67834-R, TEC2017-84423-C3-1-P, RED2018-102585-T and 0677_DISRUPTIVE_2_E