MQTT (Message Queuing Telemetry Transport) is a lightweight publish/subscribe messaging protocol designed for low-bandwidth, high-latency, or unreliable networks.

• Sensor telemetry transmission
• Event and alert messaging
• Field → Farm Controller aggregation
• Optional Farm → HQ synchronization

• Field Controller → Farm Controller
• Farm Controller → HQ / Federated Layer
• Optional local broker within farm LAN

• Low bandwidth usage
• Works well over unstable connections
• Supports retained messages and QoS levels
• Simple implementation on embedded controllers (e.g., ESP32)

• MQTT must not be used to bypass Field Controller safety logic
• Loss of MQTT connectivity must not interrupt irrigation safety functions
• All received remote commands must be validated locally
• All transmitted and received events must be logged