Operating without a network.
WHAT TO ASSUME
Connectivity is intermittent.
WHAT THE DEVICE MUST DO
Continue its function Store readings it cannot send Transmit them when connectivity returns Record that a gap occurred
WHAT STORAGE MUST BE SIZED FOR
The longest outage you expect, plus margin.
WHAT TO DO WHEN STORAGE FILLS
Discard by a defined rule: oldest first, or detail before summary.
WHY A DEFINED RULE MATTERS
Undefined behaviour loses the wrong data.
WHAT TIMESTAMPS REQUIRE
A clock the device maintains.
WHY THAT IS DIFFICULT
Cheap clocks drift, and power loss resets them.
WHAT TO DO
Synchronise time whenever connected, and record the clock's confidence.
WHAT TO NEVER DO
Timestamp buffered readings with the transmission time.
WHY
It destroys the data's meaning entirely.
WHAT RECONNECTION MUST HANDLE
A burst of stored data Duplicate transmission after uncertain delivery Many devices reconnecting simultaneously
WHAT THAT LAST POINT CAUSES
A flood after an outage, overwhelming the platform.
WHAT PREVENTS IT
Randomised delay before reconnecting.
