This is a fun thought-experiment highlighting the challenges of communicating over an unreliable channel — where your message may or may not get through, and where you won’t know if it has.

The situation is that two armies, either side of a hostile valley, are trying to coordinate an attack, and they want to attack at the same time 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…

The two generals problem

Networks effects can lead to massive, rapid growth. Amazon has leveraged this little sketch by Jeff Bezos in 2001 for mega growth — Amazon calls it a virtuous cycle — and, more recently, the Uber variation, by David Sacks explains much of Uber’s wild ride.

When you build a platform that leverages network effects right it can enable growth way beyond what has historically been possible. Also, see Metcalfe’s Law.

Sketchplanations tagged with networks