The two generals problem
The Two Generals Problem is a fun thought experiment highlighting the challenges of communicating over an unreliable channel. Your message may or may not get through, and how will you know if it didn't?
The situation is that two armies on either side of a hostile valley are trying to coordinate an attack, and they want to attack simultaneously to be sure to succeed. The trouble is, to coordinate, they have to send brave messengers through the hostile valley to the other camp, and the messengers may or may not be captured along the way.
To coordinate the attack, you have to know that your message got through, which you’d know if you received a confirmation. But how would the general sending the confirmation know that their confirmation got through unless they received a confirmation of the confirmation? And on…
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