The Willow Architecture: Comprehensive Survivability for Large-Scale Distributed Applications ; CU-CS-926-01
John C. Knight, Dennis M. Heimbigner, Alexander L. Wolf, Antonio Carzaniga · CU Scholar (University of Colorado Boulder) · 2001
The Willow architecture is a comprehensive approach to survivability in critical distributed applications.Survivability is achieved in a deployed system using a unique combination of (a) fault avoidance by disabling vulnerable network elements intentionally when a threat is detected or predicted, (b) fault elimination by replacing system software elements when faults are discovered, and (c) fault tolerance by reconfiguring the system if non-maskable damage occurs.The key to the architecture is a powerful reconfiguration mechanism that is combined with a general control structure in which network state is sensed, analyzed, and required changes effected.The architecture can be used to deploy software functionality enhancements as well as survivability.Novel aspects include: node configuration control mechanisms; a workflow system for resolving conflicting configurations; communications based on wide-area event notification; tolerance for wide-area, hierarchic and sequential faults; and secure, scalable and delegatable trust models.