Federate migration in HLA-based simulation

Abstract

The High Level Architecture (HLA) promotes simulation interoperability and reusability, making it an ideal candidate to model large-scale systems. However, a large-scale simulation running in a distributed environment is often affected by the imbalance of load level at different computing hosts. Migrating simulation components from heavily-loaded hosts to less-loaded ones can solve the problem. Protocols to migrate HLA simulation federates have been introduced by various research projects. However, existing protocols achieve migration by using either federation wide synchronization or a third party host, such as FTP servers, to handle the saving and restoring of migration states. We have previously developed a framework to execute HLA-based simulations in the Grid environment with migration support as a prominent design feature. Based on the framework, a federate migration protocol that bypasses the shortcomings identified above has been developed and better migration performance is achieved. To eliminate message loss during the migration process, a counter mechanism is employed. Studies also show that federate join time contributes significantly to the migration overhead. Therefore, our protocol overlaps the simulation execution of the federate to be migrated and the join federation operation performed by the restarting federate at the migration destination. In this paper, the development of our protocol is described and experimental results with comparison to the approach using federation wide synchronization are discussed.