User programs (web browser, mail client, and many others) interact with the DNS server through a resolver, which is also part of the operating system. The resolver interacts with external name servers that provide it with the required IPs (the name server can be local or remote; it is external to the resolver). The way the user queries the DNS server is OS specific. DNS queries and responses are sent and received between the resolver and the name server. It is shown in the following diagram:

The local name server is usually located in the organization network, and interacts with the DNS server of your ISP. In the case of a home or small office network, your DNS server can be configured on the router that connects you to the internet, or directly to the DNS server of your ISP:

• When the DNS server is on the router, you query the DNS on the router that queries your ISP DNS
• When your DNS is located on the ISP network, you query the DNS server directly