Ordering the coordinators allows each replica to distinguish between the current coordinator and previous
coordinators. In this way, replicas can reject messages from old coordinators and prevent them from disrupting
consensus once it is reached. Paxos orders the coordinators by assigning them an increasing sequence
number as follows. Each replica keeps track of the most recent sequence number it has seen so far. When a
replica wants to become coordinator, it generates a unique1
sequence number higher than any it has seen,