Distributed Systems Challenges in Wildland Firefighting Environments

The System Wide Safety (SWS) program has been investigating how manned and un-manned aircraft can safely operate in shared airspace. Enforcing safety requirements for distributed agents requires situational awareness and coordination by passing messages over a communication network. Unfortunately, the operational environment will not admit reliable high-bandwidth communication between all agents, introducing theoretical and practical obstructions to global consistency that make it more difficult to maintain safety-related invariants. Taking disaster response scenarios, particularly wildfire suppression, as a motivating use case, this self-contained memo discusses some of the distributed systems challenges involved in system-wide safety through a pragmatic lens, offering many illustrations for clarity. We explain through figures and examples the essential concepts behind the continuous consistency model for shared memory proposed by Yu and Vahdat, arguing that this model has great relevance for safety-related distributed applications that run over adversarial and disruption-prone networks.