Asynchronous Networks and Erlang Formulas

Abstract: : The paper addresses the idea of utilization of Erlang formulas in asynchronous ATM and IP networks. Based on the common properties of synchronous and asynchronous networks we have proposed the utilization of Erlang formulas not only for synchronous networks, but also for asynchronous networks. It is possible to describe traffic in asynchronous networks by calculation of following parameters -loss, link utilization and bandwidth. We present some simulation results from Matlab

Formal Model Engineering for Embedded Systems Using Real-Time Maude

This paper motivates why Real-Time Maude should be well suited to provide a formal semantics and formal analysis capabilities to modeling languages for embedded systems. One can then use the code generation facilities of the tools for the modeling languages to automatically synthesize Real-Time Maude verification models from design models, enabling a formal model engineering process that combines the convenience of modeling using an informal but intuitive modeling language with formal verification. We give a brief overview six fairly different modeling formalisms for which Real-Time Maude has provided the formal semantics and (possibly) formal analysis. These models include behavioral subsets of the avionics modeling standard AADL, Ptolemy II discrete-event models, two EMF-based timed model transformation systems, and a modeling language for handset software.Comment: In Proceedings AMMSE 2011, arXiv:1106.596

Performance comparison of scheduling algorithms for IPTV traffic over polymorphous OBS routers

Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.V. López, J. L. García-Dorado, J. A. Hernández, and J. Aracil, "Performance comparison of scheduling algorithms for IPTV traffic over polymorphous OBS routers", in ICTON Mediterranean Winter Conference, 2007. ICTON-MW 2007, p. 1-6Recent research in optical burst switched networks has proposed solutions to support subwavelength reservation for the periodic transmission of data bursts, which can coexist with conventional asynchronous bursts, bringing the polymorphous, agile and transparent optical networks (PATON) [1]. Thus, network operators can distribute IPTV channels to their customers, whereby they can use the spare bandwidth for the transmission of best-effort traffic, making use of the free gaps in between such periodic reservations. This work proposes scheduling algorithms for the transmission of periodic channels using PATON, and studies the blocking probability observed by best-effort traffic, when such scheduling algorithms are used.This work has been partially funded by the Spanish Ministry of Science and Education under the project DIOR (TEC2006-03246), and by the Comunidad Autónoma de Madrid under project e-Magerit (S-0505/TIC/000251). The authors would also like to acknowledge the support from the European Union VI Framework Programme e- Photon/ONe+ Network of Excellence (FP6-IST-027497)

Synthesising correct concurrent runtime monitors

This paper studies the correctness of automated synthesis for concurrent monitors. We adapt a subset of the Hennessy-Milner logic with recursion (a reformulation of the modal μ-calculus) to specify safety properties for Erlang programs. We also define an automated translation from formulas in this sub-logic to concurrent Erlang monitors that detect formula violations at runtime. Subsequently, we formalise a novel definition for monitor correctness that incorporates monitor behaviour when instrumented with the program being monitored. Finally, we devise a sound technique that allows us to prove monitor correctness in stages; this technique is used to prove the correctness of our automated monitor synthesis.peer-reviewe

State Aggregation-based Model of Asynchronous Multi-Fiber Optical Switching with Shared Wavelength Converters

Cataloged from PDF version of article.This paper proposes new analytical models to study optical packet switching architectures with multi-fiber interfaces and shared wavelength converters. The multi-fiber extension of the recently proposed Shared-Per-Input-Wavelength (SPIW) scheme is compared against the multi-fiber Shared-Per-Node (SPN) scheme in terms of cost and performance for asynchronous traffic. In addition to using Markov chains and fixed-point iterations for modeling the mono-fiber case, a novel state aggregation technique is proposed to evaluate the packet loss in asynchronous multi-fiber scenario. The accuracy of the performance models is validated by comparison with simulations in a wide variety of scenarios with both balanced and imbalanced input traffic. The proposed analytical models are shown to remarkably capture the actual system behavior in all scenarios we tested. The adoption of multi-fiber interfaces is shown to achieve remarkable savings in the number of wavelength converters employed and their range. In addition, the SPIW solution allows to save, in particular conditions, a significant number of optical gates compared to the SPN solution. Indeed, SPIW allows, if properly dimensioned, potential complexity and cost reduction compared to SPN, while providing similar performance. (C) 2013 Elsevier B.V. All rights reserved

A tool for model-checking Markov chains

Markov chains are widely used in the context of the performance and reliability modeling of various systems. Model checking of such chains with respect to a given (branching) temporal logic formula has been proposed for both discrete [34, 10] and continuous time settings [7, 12]. In this paper, we describe a prototype model checker for discrete and continuous-time Markov chains, the Erlangen-Twente Markov Chain Checker EÎMC2, where properties are expressed in appropriate extensions of CTL. We illustrate the general benefits of this approach and discuss the structure of the tool. Furthermore, we report on successful applications of the tool to some examples, highlighting lessons learned during the development and application of EÎMC2

Multiparty session types for dynamic verification of distributed systems

In large-scale distributed systems, each application is realised through interactions among distributed components. To guarantee safe communication (no deadlocks and communication mismatches) we need programming languages and tools that structure, manage, and policy-check these interactions. Multiparty session types (MPST), a typing discipline for structured interactions between communicating processes, offers a promising approach. To date, however, session types applications have been limited to static verification, which is not always feasible and is often restrictive in terms of programming API and specifying policies. This thesis investigates the design and implementation of a runtime verification framework, ensuring conformance between programs and specifications. Specifications are written in Scribble, a protocol description language formally founded on MPST. The central idea of the approach is a dynamic monitor, which takes a form of a communicating finite state machine, automatically generated from Scribble specifications, and a communication runtime stipulating a message format. We extend and apply Scribble-based runtime verification in manifold ways. First, we implement a Python library, facilitated with session primitives and verification runtime. We integrate the library in a large cyber-infrastructure project for oceanography. Second, we examine multiple communication patterns, which reveal and motivate two novel extensions, asynchronous interrupts for verification of exception handling behaviours, and time constraints for enforcement of realtime protocols. Third, we apply the verification framework to actor programming by augmenting an actor library in Python with protocol annotations. For both implementations, measurements show Scribble-based dynamic checking delivers minimal overhead and allows expressive specifications. Finally, we explore a static analysis of Scribble specifications as to efficiently compute a safe global state from which a monitored system of interacting processes can be recovered after a failure. We provide an implementation of a verification framework for recovery in Erlang. Benchmarks show our recovery strategy outperforms a built-in static recovery strategy, in Erlang, on a number of use cases.Open Acces