What is a resolving nameserver?
A resolving nameserver, also known as a recursive nameserver or a recursive resolver, is an essential component of the Domain Name System (DNS). It is responsible for resolving domain names on behalf of client devices and users.
When a user's computer or device needs to access a website or any other internet resource by its domain name, it sends a DNS query to a resolving nameserver. The resolving nameserver acts as an intermediary in the DNS lookup process and helps find the IP address associated with the requested domain name.
Here's how a resolving nameserver works:
DNS Query: The client device, such as a computer or smartphone, sends a DNS query to the resolving nameserver. The query includes the domain name that needs to be resolved.
Recursive Resolution: The resolving nameserver performs a recursive resolution process on behalf of the client. It starts by checking its own local cache to see if it has the IP address corresponding to the requested domain name. If the IP address is found in the cache and hasn't expired, the resolving nameserver returns the IP address to the client, and the process ends.
Iterative Resolution: If the resolving nameserver does not have the IP address in its cache, it starts the iterative resolution process. It contacts the root DNS servers, asking for the IP address of the authoritative DNS server responsible for the top-level domain (TLD) of the requested domain name.
Querying Authoritative DNS Servers: The resolving nameserver then contacts the TLD authoritative DNS server it obtained from the root DNS servers. It requests the IP address of the domain name from this authoritative DNS server.
Caching and Response: The authoritative DNS server responds to the resolving nameserver with the IP address of the requested domain name. The resolving nameserver caches this information to speed up future queries and sends the IP address back to the client device.
Client Access to the Resource: Armed with the IP address, the client device can establish a direct connection to the web server or resource associated with the domain name. The requested resource is then delivered to the client device, allowing the user to access the website or service.
Resolving nameservers play a crucial role in the DNS infrastructure by handling the complexity of the DNS resolution process and caching DNS records to improve efficiency. They act as intermediaries between client devices and authoritative DNS servers, enabling users to access websites and other online resources by their domain names.