DNS Propagation & Time to Live (TTL)

Have you ever face like this situation?  You’ve registered your domain name, paid for hosting with a hosting provider and uploaded your website to the web server. If this is all done, why can’t you see the results of your hard work right away? You ask the hosting provider’s support department and they answered “Please wait for the DNS to propagate”.You have no choice but to wait the DNS to propagate. And then it hits you,what is a DNS Propagation?

To understanding DNS propagation, you must first understand a little about how DNS works. When you set up your website with your hosting provider, they create a Master DNS record in their Domain Name Servers. Your domain registrar will points to your web host’s DNS server as being the master authority of your domain.

DNS propagation need 24 hours to propagate

When any outside source wants to know how to find your website, they first go to the registrar’s database to find out who the DNS authority is for your website. 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.

In order to speed up the rate at which their customers can view the internet, each Internet Server Provider caches their DNS records. This means that they make their own copy of the master records, and read from them locally instead of looking them up on the Internet each time someone wants view a website. This actually speeds up web surfing quite a bit, by (1) speeding up the return time it takes for a web browser to request a domain lookup and get an answer, and (2) actually reducing the amount of traffic on the web therefore giving it the ability to work faster.

The downside to this caching scenario and what makes it take so long for your website to be visible to everyone, is that each company or ISP that caches DNS records only updates them 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, since your websites DNS information is now being propagated across all DNS servers on the web. When this is finally complete, everyone can now visit your new website. Being that the cache time is different for all servers, as mentioned above, it can take anywhere from 36 to 72 hours for DNS changes to be totally in effect.

Temporarily, you can access the website or webmail using IP before you can use your domain. Example :

- For website, http:///~username [ E.g: http://124.217.242.80/~test ]
- For webmail, http:///mewebmail or http:///webmail [ E.g: http://124.217.242.180/mewebmail or http://124.217.242.80/webmail ]

Each web hosting provider has different IP URL link to view website or webmail. Thus you need to check with the web hosting provider.

Now how we have immediate DNS propagation? What is the trick? I am sure you dont want to wait 24 hrs to 72 hours for your website to be transferred to your new server. So how do we minimise DNS propagation time?  We do this by adjusting the DNS TTL (Time to Live). Before you do any migration, set your TTL to the lowest DNS server time to live (TTL). By default it is 86400 seconds (1 day). This means visitors to your website will be accessible to both old and new servers in that 24 hours. Some will go to old servers and some will go to new servers. A flip flop situation. Imagine if it is set to 3 days then you will go berserk! Can you imagine some of your emails going to old server and some to new servers? To avoid this, set the TTL to minimum of 60 seconds before you change your DNS. Set the TTL to minimum of 60 seconds, wait for 24-72 hours. By setting TTL as 60 seconds, we are telling all the servers worldwide to check your server DNS every 60 seconds for any changes. So after 24 hours all the servers worldwide would known that they need to check every 60 seconds. This is the right time you should change your website’s DNS to the new server DNS.Voila, within 60 seconds everything is migrated to the new server and all visitors will only go to the new server.

Hope this post will give you a brief understanding for DNS Propagation and the importance of TTL for seamless website migration. Until next time readers.

-Shinjiru Web Hosting-