DNS (Domain Name System) is a distributed database system used to map domain names to IP addresses. DNS provides a special method for maintaining and linking these mappings in a unified manner.
On a larger scale, computers connected to the internet use DNS to create URL links (Universal Resource Locators). Using this method, each computer does not need to use an IP address for connections but can simply use a domain name to query that connection.
Domain Name Hierarchy
To better understand how DNS operates, let’s consider an example and refer to the illustration below:
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Domain Name Hierarchy |
Example of DNS operation:
Suppose PC A wants to access the website www.yahoo.com and the local server has not yet stored information about this website. The query steps would proceed as follows:
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First, PC A sends a request to the domain management server asking for information about www.yahoo.com.
The domain management server sends a query to the top-level domain server. -
The top-level domain server stores information about all domain names on the network. Therefore, it sends back the IP address of the domain management server for .com (referred to as com server) to the local domain management server.
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With the IP address of the com domain management server, the local server queries the com server for information about yahoo.com. The com server manages all websites with the .com domain and sends the IP address of the yahoo.com server back to the local server.
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At this point, the local server now has the IP address of yahoo.com. However, PC A requested the www service, not the ftp service or any other service. Therefore, the local server continues to query the yahoo.com server to request information about the www service management for yahoo.com.
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Naturally, upon receiving the query, the yahoo.com server sends back the IP address of the management server for www.yahoo.com to the local server.
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Finally, the local server sends the IP address of the management server for www.yahoo.com back to PC A, allowing PC A to connect directly to it. Now, the local server has information about www.yahoo.com for future queries from other clients.