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Around IT In 256 SecondsAround IT In 256 Seconds

#29: Time synchronization

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Clocks are important to computers. Computers need to order events in a way understandable to humans. Every computer has a bunch of internal counters, like CPU ticks. But they only work within one machine. We need a way to have a reliable, global clock, that is synchronized between many computers. Why, exactly? Well, imagine you are selling tickets to The Rolling Stones concert. They sometimes sell within a few seconds. First come, first served. But who was first, if selling happens asynchronously in multiple data centers? Fans shouldn’t be penalized for being routed to a server with higher latency. So, instead, we use timestamps. Late messages may still be treated as earlier ones if a transaction timestamp says so. Obviously we can’t rely on the client’s clock. It’s too easy to change your laptop’s time and see Mick Jagger from the front row. But how do we make sure servers aren’t lying the same way? Even unintentionally? This is where NTP, network time protocol, comes into play.

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