TTL Power Over the Internet
Understanding TTL makes you a master over domain propagation. Time To Live notifies the world to expect changes and when. If you know what it is and how to use it to your advantage, you can command the world to take notice.
We have all seen notices from domain registrars that changes to your domain may take 24 to 72 hours to take effect. IT professionals call this propagation. The process is like a pre-school game, whispering a message in the ear of the person next to you. Even sitting next to you, the last person doesn’t get the news until they’re told. Servers actually update their information about websites and email (DNS and MX) by passing the information around. Unless a system knows about an update, it can take a very long time to catch up with your new sub domain or mail provider.
TTL tells those servers when to update routing tables down to the second. So, a TTL of 14400 is 240 minutes or four (4) hours. Every request for DNS information needs to be answered, so server administrators extend Time To Live for as long as possible. It spreads out the requests so they don’t compete with the other important tasks the server performs.
What’s a webmaster to do?
Knowledge is power and Time to Live can be changed. You can change the TTL of a single subdomain or an entire server. For example, you can move your mail between servers and providers almost instantly by changing the MX record from 14400 to 300. Now, when you move to another mail server, all your mail will follow within five minutes. We use the same method for moving a domain between servers or every domain when migrate servers.
You need to plan for the maximum benefit. you can’t change your TTL to 300 and start making immediate changes. Nothing can happen until the old Time to Live expires. The safest way make a change requires changing the TTL and waiting for the old time to expire. So, if the old time was eight hours, we change TTL to five minutes then walk away for eight hours or longer.
We can be confident that over the eight hour wait, the major routing systems got our notice that the new time is five minutes. You can change anything mail servers, A records and CNames and the internet will obey your command.