Published: Monday, January 24, 2011
To help you better understand what DNS Propagation is, it's best to learn a little about how DNS actually works. After a website has been set up with your hosting provider, a Master DNS Record is created in their Domain Name Servers (DNS). From here, the company you paid in order to own your domain name (a.k.a. domain registrar) points to your web host's DNS server which serves as the master authority of your domain.
For outside sources that are attempting to learn how to find your website, they must first locate the registration database to find out who maintains the DNS authority of your website. From there, they visit your hosting provider's DNS servers in an effort to establish your domain name's IP Address. This enables an audience to view your website.
Unfortunately, there is a downside to this process. In order to actually facilitate and speed up the rate at which customers can view the internet, each Internet Server Provider (ISP) caches their DNS records. When an Internet Server Provider (ISP) does this, it means that they create their own copy of the master records. Instead of looking them up on the Internet each time someone wants to view a website, the ISP reads from them locally. Reading the cached records locally helps to speed up the return time involved when it comes to a web browser requesting to lookup a domain for an answer. It also helps to reduce the amount of traffic on the web, ultimately allowing it to work much faster.
The biggest disadvantage to this process is the fact that it is typical for each company or ISP to update their cached DNS Records every few days. While it is not thought of as a standard, these companies or ISP's can schedule these updates to take place anywhere from every few hours to several days apart. This slow form of updating a server's cache is referred to as propagation because your website's DNS information will be propagated across all DNS servers on the web. Once this process is completed, your website will be up, running and catering to your audience. Ultimately, it can take anywhere from a day to several days for DNS changes to be in effect since the cache time is different for all servers.