Definition:

When a new domain name is registered (or an existing one is transferred to a new DNS), the information must make its way around the entire internet. This process usually takes around 24 hours, during which time the domain will be inaccessible to many or all users. The duration between no availability and availability of new domain is generally called DNS propagation.

Here we will look with an example. Suppose, you have hosted one domain and registered it with standard registrar, now you have also uploaded your web contents. After completing this whole process, you are going to browse your site. But surprise..!!! you can not access your site. Why..?? This is because of DNS propagation.

DNS Propagation:

First you have to understand how DNS works, in order to understand DNS propagation. You have paid for your hosting service to any hosting provider. Now hosting provider will set up your site on their server. Your domain will setup on particular IP address. Your hosting provider creates a “MASTER” record in their DNS (Domain Name Servers) for your domain. Now turn around at your domain registrar. Domain registrar set the appropriate Nameservers to point the exact server where your web contents are hosted. They can be the master authority of your domain. They can change the nameservers as per requirements.

Whois lookup:

The details of domain authority and honor of domain is called whois record.
When any outside source wants to know how to find your website, they first go to the registration database to find out who the DNS authority is for your website (Registrar of your domain). Then they visit your hosting provider’s DNS servers to find out what the IP Address is for your domain name, and from there your audience can now view your website.

Sometimes problem causes because of ISP (Internet Service Provider) caches. This is the biggest problem of DNS propagation. ISPs make their own copy of master records and read from them locally instead of looking them on the Internet each time any user wants to view a website. Hence, sometime we can view the changes made by us because of ISP caching. ISP caching is beneficial to increase the surfing speed, decrease request time and reduce the web traffic. These all matters increase the speed but sometimes cause the caching problem.

The problem to this caching scenario is that each company or ISP clears the Internet cache every few days. This is not any kind of standard, and they can set this time anywhere from a few hours to several days. The slow updating of the servers cache is called propagation. When the task of DNS propagation finally completes, every user can now visit your new website. But one should note that this propagation will take near about 36 to 72 hours for DNS changes to be totally in effect.