Karl Denninger supposedly said:
You're making lots of assumptions.
1) That client DNS systems will actually honor such a TTL. Many
don't (claim they're broken all you want, but these are the facts).
2) That client SOFTWARE will actually go back and ask again for the
IP number. Several won't (Netscrape being rumored to be one of
them). TTLs are irrelavent in that case.
Go ahead and try to tell your customer, who purchased web service from you,
that you have the right to disrupt their operations at any time and under
any pretense and see how many of them you have left.
How do you handle hardware upgrades, random crashes, etc. with your
clients? Do you give them a refund for such downtimes? DO you guarentee
that every client that tries to access their web page will always get
My guess is you don't. You perform a service for them and probably
schedule maintenence in such a way as to minimize downtime and impact on
If you have a better scheme, like fully redundent machines that fall over
automatically and let you do maintenence on one while the other opperates
then I think you have done an excellent job at providing a quality service
for your customers. On the other hand, someone who has done such a setup
should realize how easy it would be to migrate it to different addresses
while maintaining pretty much complete connectivity for the old addresses
for a reasonable time (like a standard TTL length).