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DNS TTL and Propagation1:47 with Jason Seifer
When changes are made to a domain name, they are not always immediately picked up because of the Time to Live (TTL) property. Learn more in this video!
- Time to Live: a mechanism that limits the lifespan or lifetime of data in a computer or network - Wikipedia
- Propagation: the process of the changes being picked up across the Internet
Before we get too deep into how the domain name system works
we need to understand a couple of terms when working with domains.
One of those terms is called Time To Live or TTL.
Now, this is not just a metaphor for how you should live your life.
This actually specifies the number of seconds,
in which information should be updated.
So your computer might be looking for updates to different information
such as where a specific server is on the internet.
Now, DNS is a very, very distributed system
and this is where the term propagation comes in.
Certain information will be distributed all throughout the globe
and backed up.
Now, when you specify a very low time to live
and a low number of seconds
it will take less time for information to be fetched
When you specify a really high TTL
it will not be looked up as often.
Now as you might imagine, setting a really high time to live
would be very beneficial in certain situations.
This would mean information won't need to be queried as much,
which would be reduced load on your DNS servers.
When you're developing or testing applications
it's useful to set a very low time to live.
This way you can make sure changes get picked up a lot quicker.
When you move into production, it's generally better
to set a high time to live so that clients won't be fetching new information
a lot of the time.
In the case that you're switching servers—for example—
moving your www server from one host to another
it's beneficial to reset the time to live from a high value
to a low value in preparation for the move.
You don't need to worry too much about TTL right now,
but it is something that we'll keep in mind for later.
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