When moving web host to another hosting service’s server or changing the server’s IP address, one of the important consideration to ensure to continue availability of the websites hosted on the server, minimize the downtime of the web sites, avoid weird problems such as emails get delivered to either server randomly, or browsing at old server, is how fast DNS (Domain Name System) will be able to translate or resolve hostname or domain name into your new IP address, instead of the old IP destination. Unfortunately, webmasters have limited ability to control or override the DNS propagation process. Nonetheless, there are still some tips, tricks and workarounds that ensure DNS cache will reflect the new IP addresses as soon as possible.
DNS works in such as a way that when a request for IP address received by DNS resolver, it will then query the root servers to find the authoritative server with detailed knowledge of the particular domain name. If a valid IP address for the domain is returned by the authoritative server, the DNS resolver will cache the DNS resolution for a given period of time known as TTL (Time To Live) after a successful answer, in what known as DNS caching in order to reduce the load on particular DNS server. DNS caching allows resolution of domain name to IP to take place locally using the cached information instead of querying the remote server for subsequent requests, until the TTL duration expires.
The Time-To-Live (TTL) timer is the trick to ensure that the DNS cache expires quickly and always stays fresh. TTL is defined by domain administrator in the authoritative DNS server for the zone where data originates, and its values instruct DNS caching resolvers to expire and discard the DNS records after TTL seconds. Lowering the TTL value will enable rapid expiration and refreshing of DNS records, causing the new records to propagate faster across the world. However, the trick needs the name resolvers follow the RFC standards, which most do. Beside, you must have full control to modify the name server authoritative for your domains. (more…)