On 9/7/18 10:05 PM, John Reid wrote:
Hi all,discussion of how to keep accurate time without access to GPS seems very on topic to me. These people involved in major catastrophe ('end of the world' as you put it) scenarios have a wealth of experience in other ways of keeping accurate time.
Actually, they don't necessarily have a wealth of experience, because they may have marched themselves down a path where they have a *requirement* for much better timing than they realize, because it is so easy and cheap to get good time today.
Imagine this scenario - you're a bank, and you batch process checks and deposits in one physical location, so you don't much care about when the check was written or the deposit made. Then you move to a distributed system across the US, where the reconciliation is done on the basis of the date of the transaction - still probably ok, because there are no transactions during non-business hours, so as long as you reconcile at 1AM, if transaction time stamps are off by 5 minutes, it doesn't matter.
Now say "we're going to charge you, the customer a fee, if your balance goes negative" and go to 24/7 operations, where transactions are journaled immediately, rather than batch processed at night If a deposit that was made at 12:00 (but timestamped 12:05) is followed by a withdrawal made at 12:03 (but timestamped 12:00), you get unfairly charged the overdraft fee.
For small problems, banks have ways to "unwind" errors. But if it becomes a systemic thing that's a problem.
So the bank sets up GPSDOs at each transaction point - problem solved. Until GPS fails. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
