Before 2004 Verisign only updated the authoritative DNS twice a day.
Then they changed it in January 2004 to every five minutes.
So yes, if you are an "old timer" you may remember it really taking up to 48 hours for everywhere around the world to be able to find a new .com
But also what they mean by 48 hours is for existing DNS, some users around the world may be on ISPs that heavily cache DNS.
Even wifi routers today have some persistent DNS caches and people rarely reboot or turn them off.
We moved a site a few weeks ago and the old IP still got some hits until last week. I gave up trying to trick all the caches and just used iptables to forward the packets from the old server to the new until everything finally caught up.
That's true, but "48 hours to propagate" is misleading because it sounds as though that's business as usual for DNS -- instead of the reality, in which rogue DNS servers cache beyond domains's declared TTL.
Explaining that to clients is hard. We say "it'll take about 72 hours for everything to sync over". If we're switching them to a new IP, we'll leave the old server on until 72-96 hours after we update DNS. We seriously still see traffic on the old server that long after the change, and ~72 hours is about how long it takes to get ~99% updated.
Then they changed it in January 2004 to every five minutes.
So yes, if you are an "old timer" you may remember it really taking up to 48 hours for everywhere around the world to be able to find a new .com
But also what they mean by 48 hours is for existing DNS, some users around the world may be on ISPs that heavily cache DNS.
Even wifi routers today have some persistent DNS caches and people rarely reboot or turn them off.
We moved a site a few weeks ago and the old IP still got some hits until last week. I gave up trying to trick all the caches and just used iptables to forward the packets from the old server to the new until everything finally caught up.