Sever Lock-Step

I generally understand the lock-step system but I have one ambiguity.

When one client sends commands to another client, when does it plan to execute the command? In a fixed time, expecting the other client to do the same at that moment? Will the first client need cnfirmation from the other client to execute that command and how is the time to send the confirmation accounted for?

Read the two articles here:

He even provides the sourcecode which makes it wonderful to understand!

The secret was NetworkMessageInfo.TimeStamp! Just factor that in the latency calculations and bam, lock-step!