Numbers To Know hard
NTP (Network Time Protocol) generally synchronizes servers across the internet to within what accuracy?
- A within 1 nanosecond
- B within 1 microsecond
- C within 10 to 100 milliseconds
- D within 1 minute
Answer: C. within 10 to 100 milliseconds
Synchronizing time across the internet via NTP is limited by the 'jitter' of network routing. Because packets can take slightly different paths each time they travel to a time server, NTP can generally only guarantee accuracy within 10-100 milliseconds. While this is fine for log files, it's not enough for 'Distributed Transactions' where you must know exactly which of two events happened first globally. Systems like Google Spanner solve this by using 'TrueTime'—a hardware-based clock system using atomic clocks and GPS in every datacenter to keep synchronization bounds within a tight 1-3 millisecond window.
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