Eager Queue Protocols were developed as a way of monitoring the state of distributed processors. What was wanted was an idea of how "live" the processors were. The first approach was to have each processor transmit a heartbeat and a record was kept of the heartbeats. The initial idea was to keep the record centrally, then it appeared better to have each processor keep its own copy of the heartbeat history. The heartbeat history or LKT (last known transmission) vector would be an array of processor Ids and the time when the processor last transmitted, see OpenEd-Lab4.