DNS propagation and Why does it Take so Long?
First off, you may be asking what is DNS, let alone why would I want this propagated. DNS stands for Domain Name System and is the way that Internet domain names (like zeroonezero.com) are located and then changed or more correctly translated into IP address (that’s these things ’220.127.116.11′). We do this because humans like words, as they are easy to remember, but computers need addresses in numbers.
Each machine on the Internet has its own unique number, which is its IP address. So when you type in zeroonezero.com you’re really asking your browser to look for that information at this address ’18.104.22.168′. The domain name system is really a giant database, probably the biggest and most used database in the world. No only does it handle billions of lookup requests but it is also changed each day by millions of different people. This is where the propagation part comes in.
If you kept and maintained a central list of all domain names and IP addresses, it would be monumentally impractical. Therefore, this list is distributed throughout the Internet in a hierarchy of authority. Your domain registrar, for example Go Daddy, points your domain name to a DNS server. This becomes the master authority of your domain. When a request is made to find a website, it goes to the registration database and finds out the DNS authority. Then it goes to that DNS server to find out what the IP Address is for your domain name.
The problem is, each Internet Server Provider (like Verizion or Comcast) caches their DNS records. This means making a local copy of the database and is done to speed up websurfing as you are able to lookup a domain faster. The downside to this is each company updates their local database with its own timeframe, which could be hours or could be days.
This updating of cache is called propagation and our website’s DNS information is now being propagated across all DNS servers on the web. So it can take anywhere from 12 to 72 hours for all computers to see the the correct location of a websites once it has been changed.