DNS Propagation Time
By Jithin on July 8th, 2016
In this documentation, we can learn about DNS propagation time and the factors which affect DNS propagation time.
DNS stands for domain name server and is used anytime we visit the internet. It is a lookup table that resolves internet web addresses to their IP addresses. DNS propagation occurs when we update the nameservers of our domain, move the domain name from one host to another, or from one server to another. Whenever the DNS changes it has to propagate completely. This process can take anywhere from between a few hours to many days. This is because when we request for a domain, the request is not going to the hosting server directly. Instead, it has to pass through many ISP nodes in different locations. DNS propagation time depends upon several factors which include the domain, host, and the domain registrar.
When we request for a domain (example:domain.com), the request goes to the local DNS server of our ISP (Internet Service Provider). Local DNS server will check the cache if it already knows the IP address of the domain name we requested. If it exists, it delivers the requested page. If it does not then it will send the query to the root DNS server. The root DNS server makes this process work. When a domain is registered, it is added to the root servers. When a domain has expired, it is removed from the root servers.
The root servers communicate to the local DNS server which DNS servers are authoritative for the domain. The local DNS server then queries the authoritative server. The authoritative server tells local DNS server what IP address the domain is located at and other necessary information. The local DNS server makes a copy of this information. This caching process is essential because it speeds up future queries and also reduces the load on the root servers. This caching process leads to quick propagation times. If we change the DNS records for our domain, then the local DNS server cache will be updated with the new information. The local DNS server does not keep this information forever. It only keeps the information for a certain amount of time. If we want to visit the same domain again after the information is deleted, the process starts again and the local DNS server updates its cache with new information. This parameter is called TTL (Time to Live).
DNS Propagation Checker
To check the propagation status at several locations worldwide, we can check this link: (https://www.whatsmydns.net/)
This website will check the domain names, current IP address, and DNS record information against multiple name servers located in different parts of the world.
This allows to check the current state of DNS propagation after changing domains records.
Factors affecting DNS propagation time: –
Time to Live is the time period for which servers cache the information for DNS records. You can configure TTL for each record in domain names zone file. Shorter TTL settings can increase propagation speed. However, shorter settings also increase the number of queries to your authoritative nameserver, and that increased load slows down your server’s processing time. The modification of a zone record’s TTL and then chaning the actual record right away will not increase the propagation time of your DNS changes. The new TTL needs to be cached at the ISP prior to the DNS change in order for you to take advantage of the shorter TTL. If you wish to speed up DNS propagation for your own personal zone records, it is recommended that you modify the TTL to a shorter time period many hours prior to modifying the DNS records.
ISPs will store data locally to speed up browsing which reduces propagation time. In order to speed up the internet browsing experience for their customers, each Internet Server Provider (ISP) caches (stores) DNS records. This means that after a customer of a particular ISP views your website or sends you an email, the ISP keeps a record of what name servers your domain name was delegated to and what zone records existed on those name servers. When a new customer from the same ISP attempts to view your website or email you, the ISP will find the cached record that it saved locally on their system instead of looking up the records on the Internet. This saves time and provides the user a faster internet browsing experience.
Domain name’s Registry
If we change the domain name’s name server, registries update their zones within minutes. Then they publish your authoritative NS (nameserver) records to their root zone. Most registries update their zones promptly. However, not all registries make updates that quickly. Registries often protect their root name servers from overuse by setting a high TTL of up to 48 hours or more for those NS records. In addition, even though recursive name servers should not cache the root NS records, some ISPs cache the information anyway. This can result in a longer nameserver propagation time.
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