I recently moved this site to a better server as my earlier server was giving problems. But, though I updated the DNS settings correctly, I could view my site only from my old server. This is when I learnt about DNS Propagation.
What is DNS Propagation?
Before trying to understand what DNS Propagation is, one should know the terms involved in that.
Before trying to understand what DNS Propagation is, one should know the terms involved in that.
DNS – Domain Name System. When you enter a webpage name, the computer internet network should identify from which server it should get the page’s content from. This is like referencing a phone book. The network doesn’t work with website name but rather it’s associated IP address. The DNS has redirection links from the meaningful site names to network recognizable IP address.
Domain Registrar Control Panel – These are the agents with whom one registers their website name. They provide a control panel where one can change their DNS settings.
Worlds DNS Servers – There cannot be a single DNS to maintain all the requests in this world so there are numerous servers which refer to Worlds DNS Servers.
Root Name Servers – Currently there are 13 Root Name Servers which are the Top level Domain (TLD) Name servers. These are nothing but DNS Servers which are the officially declared global name servers.
ISP – Internet Service Provider. These are the organization which provides internet service to you.
Short Explanation:
When you change the DNS setting in your Domain Registrar Control Panel, that setting information should be passed on to all the DNS servers in the world which is eventually used to update the DNS servers of the ISP (Internet Service Provider).But this takes time, so there is a delay from the time you actually change the setting and that being effected throughout the world. This is known as DNS Propagation.
When you change the DNS setting in your Domain Registrar Control Panel, that setting information should be passed on to all the DNS servers in the world which is eventually used to update the DNS servers of the ISP (Internet Service Provider).But this takes time, so there is a delay from the time you actually change the setting and that being effected throughout the world. This is known as DNS Propagation.
Detailed Explanation: Why there is DNS Propagation Delay?
The Root Name Servers are the ones which have the correct information regarding the DNS setting of all websites at any point of time. To maintain their accuracy, they constantly query ‘Domain Registrars’ throughout the day. When anybody changes the DNS setting, then it is being passed onto the Root Name Servers. All the major DNS servers get it updated with the information from Root Name servers. To reduce the turnaround time of the DNS lookup, all the ISP have their own DNS cache which stores these information from DNS. These caches should be set to expire in a stipulated time so that it refreshes with the latest information from DNS. But most of the ISP has their cache to expire only in 2 – 3 days. During this time if you have changed your DNS setting, it may take up to 3 – 4 days to see this new DNS setting being effected and till then it will show the contents from the old server rather than the new server. Sometimes there maybe occurrences where you are able to view the site with updated setting from office but not from home, this maybe because the office ISP have updated their local DNS but the home ISP has not updated its DNS. There may also be weird cases where your site is swinging between old server and new server in the same ISP; this means that the ISP cache is getting updated. If it takes more than 3 – 4 days, you might have problem with the new host server’s DNS setting and you have to contact them to rectify it.
The Root Name Servers are the ones which have the correct information regarding the DNS setting of all websites at any point of time. To maintain their accuracy, they constantly query ‘Domain Registrars’ throughout the day. When anybody changes the DNS setting, then it is being passed onto the Root Name Servers. All the major DNS servers get it updated with the information from Root Name servers. To reduce the turnaround time of the DNS lookup, all the ISP have their own DNS cache which stores these information from DNS. These caches should be set to expire in a stipulated time so that it refreshes with the latest information from DNS. But most of the ISP has their cache to expire only in 2 – 3 days. During this time if you have changed your DNS setting, it may take up to 3 – 4 days to see this new DNS setting being effected and till then it will show the contents from the old server rather than the new server. Sometimes there maybe occurrences where you are able to view the site with updated setting from office but not from home, this maybe because the office ISP have updated their local DNS but the home ISP has not updated its DNS. There may also be weird cases where your site is swinging between old server and new server in the same ISP; this means that the ISP cache is getting updated. If it takes more than 3 – 4 days, you might have problem with the new host server’s DNS setting and you have to contact them to rectify it.
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