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The Avionics Full Duplex Switched Ethernet (AFDX) has been developed to provide reliable data exchange with strong data transmission time guarantees in internal communication of the aircraft. The AFDX design is based on the principle of a switched network with physically redundant links to support availability and be tolerant to transmission and link failures in the network.In this work, we develop a formal model of the AFDX frame management to ascertain the reliability properties of the design. To capture the precise temporal semantics, we model the system as a network of timed automata and use UPPAAL to model-check for the desired properties expressed in CTL. Our analysis indicates that the design of the AFDX frame management is vulnerable to faults such as network babbling which can trigger unwarranted system resets. We show that these problems can be alleviated by modifying the original design to include a priority queue at the receiver for storing the frames. We also suggest communicating redundant copies of the reset message to achieve tolerance to network babbling. Comments Copyright 2006 IEEE. Reprinted from the 9th IEEE International Symposium on Object-oriented Real-time Distributed Computing (ISORC 2006), pages: 393-399This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Pennsylvania's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.

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The term "Model based design and development" has grown in popularity over the past decade. Within the embedded avionics community the term model based design implies the development and application of "control models and simulations" within tools such as MATLAB. At Honeywell, the authors have been engaged in model based development (MBD) and associated tools development for avionics applications. This position paper applies the lessons learned and discusses several issues, relating to sound modelbased design, to meet design assurance and certification objectives. The paper examines the dominant approaches utilized by some of the popular model-based design, code generation and verification tool suites available commercially. It contrasts these approaches to traditional software design, implementation, and verification methods. This paper also recommends taking a broader perspective of MBD and suggests adopting lessons learned from the classical software engineering arena. We discuss this together with areas for future investigation, standardization, and automation tool development and integration