What is Caching in Domain Name Resolution (DNR) hosting?
By: shilpa dws | Posted: 10th February 2011
Many times instead of performing the domain name resolution every time, the name servers use the concept of the caching which saves the searching. Every server maintains the cache of the recently used names as well as the record of where the mapping information of the name where it was obtained. So, basically when a client asks the server to resolve the name according to the standard procedure which means that server is in the same domain name server or the domain. If it is not so, then the server checks the cache to see if the name has been resolved recently or not. So, the servers report the cached information to the clients, but the mark is generally at the non authorative binding and gives the domain name of the server S from the binding which is obtained at the last step.
If the servers which have the cached information then it’s the first time where it’s requested and it never changes the entries into the cache which could sometime become incorrect. So, for keeping the cache correct, the server keeps the record of each entry when it is asked, and disposes the entries that exceed a reasonable time. When the server is asked for the information, after it has removed the entry from the cache, it must go through the whole process of the domain name resolution again. Then the name resolution again contacts to the authorative source and obtains the binding again. So, whenever there is a remote domain name server which responds to the request, it includes a TTL (Time to Live) value in the response that specifies the longevity of the cycle which guarantees a binding which mentions the remaining time. So, thus the authorities can reduce the network which overheads the time by specifying the long timeouts for the entries which are expected to remain unchanged as well as the value remains the same as that of the domain name servers present at the host field.
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