Knowledgebase: Umbrellar Support
What is Domain Name Servers?
Posted by Sinan Esen on 03 September 2015 02:08 PM

Overview.

Domain Name Servers (DNS) can be thought of as the phonebook of the Internet. DNS is responsible for providing up to date information on such things as where your website is hosted and where everyone should send email to.


How does it work?

Every time your type web address(URL) into a browser address bar, or send an email, you are using DNS. This means that DNS is used hundreds of millions of times every day by people using the Internet. To avoid bottlenecks and server overload, the DNS system is designed to be a distributed database. This is the key point in DNS propagation time. Here is a simplistic example. If you choose to visit www.coke.com, and you have not visited that website prior to this point, the authoritive DNS server (Name Servers) that holds the information for www.coke.com is contacted, and the database for that site is downloaded to your local network. The downloaded database has included in it a Minimum Time To Live (TTL) and this TTL dictates how long the database should be stored on your local network. A standard TTL is 12 hours.

If you then request the website www.coke.com during the TTL, there is no request back to the original name servers for www.coke.com as it is now available on your local network. This is how DNS distributes the load.

The implications of this distributed loadsharing means that if you change any information in your DNS database, such as where your website is hosted or the name servers associated with your domain, and someone has recently downloaded your DNS database, then that person will continue to use the old (Stale) information until the TTL has expired.


DNS Explaination scheme (securityaffairs.co):

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