WOPANets: A Tool for WOrst Case Performance Analysis of Embedded Networks

Ref-Nr: TDO0161

Technology abstract

WOPANets (WOrst case Performance Analysis of embedded Networks) is a design-aided decision software tool for switched embedded networks. This tool offers the designer an ergonomic interface to describe the network and the circulating traffic and embodies a static performance evaluation technique based on Network Calculus theory combined with optimization analysis to support early system level design exploration for embedded networks.

Technology Description

With the increasing complexity of switched embedded networks and the growth in the quantity of data being exchanged, making the right design decisions to guarantee the system?s requirements becomes a difficult task for a designer. Hence, one of the major challenges in the design process is to analyze the system?s characteristics as part of the first steps of the development cycle.

Simulations are commonly used for exploring the design space and validating the functional and timing behavior of the embedded networks. However, these approaches are feasible for only small parts of the system and cannot cover the entire domain of applicability of the model and, especially, rare events that represent worst-case functioning of the system. So, clearly, simulations cannot provide the deterministic guarantees required by critical embedded networks with hard certification requirements to respect as in civil and military avionics, automotive and satellites, where a failure might have a disastrous consequence on the system. With a formal specification language like StateCharts or Specification and Description Language (SDL), it is possible to verify the functional behavior of the network. However, for big communication networks with an important number of nodes (connection or redistribution point, communication endpoint), this approach leads to out-of-memory errors inherent to the reachability analysis techniques implemented by the formal verification tools.

To overcome these limitations, it is necessary to integrate an aided-decision tool into the first steps of the design process so as to choose the right system parameters that meet the required constraints before investing too much time in detailed implementation. WOPANets (Worst Case Performance Analysis of embedded Networks) is a new tool that embodies an analytical approach based on Network Calculus formalism to perform a system level worst-case performance evaluation and includes optimization analysis to find the optimal design solution that guarantees the system?s requirements. This approach saves on the time and cost of the design process. Some avionics and space networks are already implemented in WOPANets, like AFDX and Spacewire, and new models for applications based on multi-cluster embedded networks and wireless technologies are in progress.

Innovations & Advantages

Innovations:

  • Computes worst-case network metrics using Network Calculus theory
  • Overcomes simulation limitations: fast, handles large networks, implementation agnostic
  • Automatically find optimal network configuration
  • Scalable and easy to extend

Advantages for the embedded network designers:

  • Minimize over-dimensioning of hardware resources
  • Guarantee worst-case performance
  • Helps to design scalable and reusable systems

Further Information

The WOPANets tool can handle the following parameters:

  • Traffic types: periodic traffic and aperiodic traffic with and without jitter.
  • Different communication types: unicast, multicast and broadcast.
  • Technology types: many technologies are supported by WOPANets like Ethernet, AFDX and SpaceWire.
  • Different scheduling policies like First Come First Served (FCFS), Static Priority (SP), Weighed Fair Queuing (WFQ), Round robin (RR); and many control mechanisms like TDMA, Master/Slave and Token Ring.
  • Different performance metrics like: end-to-end delays, used memory, network load and loss rate.
  • ? Different optimization constraints (temporal and hardware), different variable parameters (discrete and continuous) and mono objective criteria.

Current and Potential Domains of Application

With the increasing complexity of embedded networks and the expansion of exchanged data quantity, the design aided-decision tool Wopanet could find new applications in aeronautics, automotive, railways and defense:

  • Embedded network design or upgrade
  • Support for certification
  • Network technology assessment