Friday, February 16, 2018

How DNS work

Step 1. The browser sends a query to the local DNS server in your network.

Step 2. If the local network has no internal DNS server or the DNS server has no information about the site you want to visit, a query is sent to the recursive DNS server of your Internet service provider (ISP). If the recursive server has information about the IP address in its cache, your browser receives that information. No additional queries are performed.

Step 3. However, if the recursive server does not know the IP address, the recursive server sends the query to one of the 13 sets of root name servers located worldwide. A root server knows the DNS information about a top-level domain (TLD).

Step 4. The DNS server of a TLD sends information about the second-level domain and its authoritative name server. An authoritative name server knows all the addressing information for a particular domain.

Step 5. The authoritative name server responds to a query by returning the Address Record (A record) to your ISP. The ISP’s recursive server stores the record on its cache for a specific amount of time and sends the IP address to your browser.