6,181 research outputs found
Applying Formal Methods to Networking: Theory, Techniques and Applications
Despite its great importance, modern network infrastructure is remarkable for
the lack of rigor in its engineering. The Internet which began as a research
experiment was never designed to handle the users and applications it hosts
today. The lack of formalization of the Internet architecture meant limited
abstractions and modularity, especially for the control and management planes,
thus requiring for every new need a new protocol built from scratch. This led
to an unwieldy ossified Internet architecture resistant to any attempts at
formal verification, and an Internet culture where expediency and pragmatism
are favored over formal correctness. Fortunately, recent work in the space of
clean slate Internet design---especially, the software defined networking (SDN)
paradigm---offers the Internet community another chance to develop the right
kind of architecture and abstractions. This has also led to a great resurgence
in interest of applying formal methods to specification, verification, and
synthesis of networking protocols and applications. In this paper, we present a
self-contained tutorial of the formidable amount of work that has been done in
formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial
Re-verification of a Lip Synchronization Protocol using Robust Reachability
The timed automata formalism is an important model for specifying and
analysing real-time systems. Robustness is the correctness of the model in the
presence of small drifts on clocks or imprecision in testing guards. A symbolic
algorithm for the analysis of the robustness of timed automata has been
implemented. In this paper, we re-analyse an industrial case lip
synchronization protocol using the new robust reachability algorithm. This lip
synchronization protocol is an interesting case because timing aspects are
crucial for the correctness of the protocol. Several versions of the model are
considered: with an ideal video stream, with anchored jitter, and with
non-anchored jitter
Re-verification of a Lip Synchronization Algorithm using robust reachability
The timed automata formalism is an important model for specifying and analysing real-time systems. Robustness is the correctness of the model in the presence of small drifts on clocks or imprecision in testing guards. A symbolic algorithm for the analysis of the robustness of timed automata has been implemented. In this paper we re-analyse an industrial case lip synchronization protocol using the new robust reachability algorithm.This lip synchronization protocol is an interesting case because timing aspect are crucial for the correctness of the protocol. Several versions of the model are considered, with an ideal video stream, with anchored jitter, and with non-anchored jitter
How to stop time stopping
Zeno-timelocks constitute a challenge for the formal verification of timed automata: they are difficult to detect, and the verification of most properties (e.g., safety) is only correct for timelock-free models. Some time ago, Tripakis proposed a syntactic check on the structure of timed automata: If a certain condition (called strong non-zenoness) is met by all the loops in a given automaton, then zeno-timelocks are guaranteed not to occur. Checking for strong non-zenoness is efficient, and compositional (if all components in a network of automata are strongly non-zeno, then the network is free from zeno-timelocks). Strong non-zenoness, however, is sufficient-only: There exist non-zeno specifications which are not strongly non-zeno. A TCTL formula is known that represents a sufficient-and-necessary condition for non-zenoness; unfortunately, this formula requires a demanding model-checking algorithm, and not all model-checkers are able to express it. In addition, this algorithm provides only limited diagnostic information. Here we propose a number of alternative solutions. First, we show that the compositional application of strong non-zenoness can be weakened: Some networks can be guaranteed to be free from Zeno-timelocks, even if not every component is strongly non-zeno. Secondly, we present new syntactic, sufficient-only conditions that complement strong non-zenoness. Finally, we describe a sufficient-and-necessary condition that only requires a simple form of reachability analysis. Furthermore, our conditions identify the cause of zeno-timelocks directly on the model, in the form of unsafe loops. We also comment on a tool that we have developed, which implements the syntactic checks on Uppaal models. The tool is also able to derive, from those unsafe loops in a given automaton (in general, an Uppaal model representing a product automaton of a given network), the reachability formulas that characterise the occurrence of zeno-timelocks. A modified version of the CSMA/CD protocol is used as a case-study
Platform Dependent Verification: On Engineering Verification Tools for 21st Century
The paper overviews recent developments in platform-dependent explicit-state
LTL model checking.Comment: In Proceedings PDMC 2011, arXiv:1111.006
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