How does DNS (Domain Name System) work?

The Domain Name System (DNS) is a hierarchical and decentralized system that translates domain names (like pagematics.com) into IP addresses (like 142.250.114.104), which are used to locate and communicate with resources on the internet. Here's how it works:

1. A client device (such as a computer or smartphone) sends a DNS query to a local DNS resolver. The query contains the domain name that the client wants to access.
2. If the local DNS resolver has a cached record for the domain name, it returns the corresponding IP address to the client. Otherwise, it sends a request to a root DNS server.
3. The root DNS server responds with a referral to the Top-Level Domain (TLD) DNS server that is responsible for the domain's top-level domain (such as ".com" or ".org").
4. The local DNS resolver then sends a query to the TLD DNS server, which responds with a referral to the authoritative DNS server for the domain name.
5. The local DNS resolver sends a query to the authoritative DNS server, which responds with the IP address of the requested domain name.
6. The local DNS resolver caches the IP address and returns it to the client.
7. The client uses the IP address to connect to the requested domain and retrieve the desired content.

It's worth noting that the DNS system is distributed across a large number of servers and networks. There are 13 root DNS servers worldwide, which are managed by different organizations, and each TLD has its own set of DNS servers. The authoritative DNS servers for individual domains are typically managed by the organizations that own the domain names. When a DNS query is made, it is routed through this distributed network of DNS servers until the correct IP address is returned to the client. This hierarchical and decentralized structure helps to ensure the reliability and scalability of the DNS system.

DNS Server

A DNS server is a computer server that contains the database of public IP addresses and their corresponding host names. When a client device requests the IP address for a domain name, the DNS server will respond with the corresponding IP address. There are different types of DNS servers, such as authoritative DNS servers, which store the DNS records for a specific domain, and caching DNS servers, which store recently accessed DNS records to speed up DNS resolution.

DNS Recursor

A DNS recursor (also known as a DNS resolver) is a server that is responsible for answering DNS queries on behalf of client devices. The DNS recursor exists as a software component that runs on a server. Typically, the DNS recursor is run by Internet Service Providers (ISPs), but it can also be run by organizations or individuals that want to provide DNS resolution services.

When a client device sends a DNS query, the query is sent to a DNS recursor, which then looks up the requested domain name in the DNS hierarchy to find the corresponding IP address. If the DNS recursor already has the requested DNS record in its cache, it returns the answer to the client device immediately. If it does not have the answer in its cache, it forwards the query to other DNS servers until it finds the answer or determines that the requested domain name does not exist.

In summary, the DNS recursor exists as a software component running on a server that provides DNS resolution services for client devices.

Root Name Server

A root name server is a server that forms the backbone of the global domain name system (DNS). There are 13 root name servers in the world, labeled A through M. These servers are responsible for answering DNS queries and providing authoritative responses for top-level domains (TLDs) such as .com, .org, .net, .gov, .edu, and country code TLDs such as .us, .uk, .ca, etc.

The root name servers are maintained by different organizations around the world, including the Internet Corporation for Assigned Names and Numbers (ICANN) and various national domain name registries. The servers are distributed geographically to ensure redundancy and resilience, and they use anycast routing to provide efficient and reliable responses to DNS queries from all over the world.

Whenever someone enters a URL in a web browser or sends an email, their device sends a DNS query to a DNS resolver, which in turn queries the appropriate root name server to determine the IP address associated with the domain name. The root name server then responds with a referral to the appropriate TLD server, which can then provide the IP address of the specific server that hosts the requested content.

The number of IP addresses used to query the root servers remains at 13, and this is a fundamental limit imposed by the design of the DNS. However, each of these IP addresses is associated with multiple servers located in different parts of the world, and Anycast routing is used to distribute queries to the server that is closest to the requester, both geographically and in terms of network topology.

There are now over 600 DNS root servers distributed across the world, and they are operated by a variety of organizations. However, they all fall under one of the 13 IP addresses used to query the root servers, and this is a fundamental aspect of the DNS architecture that has not changed.

TLD (Top Level Domain) Name server

A TLD (Top Level Domain) Name server is a DNS server that is responsible for managing the domain names within a specific top-level domain (TLD). For example, the .com TLD Name server is responsible for managing all domain names that end with .com, such as example.com or pagematics.com.

Each TLD has its own set of Name servers, which are authoritative for that TLD. The TLD Name servers store information about the domain names within that TLD, including the IP addresses of the DNS servers that are authoritative for the individual domain names within the TLD.

When a DNS resolver receives a query for a domain name within a specific TLD, it sends the query to the TLD Name server for that TLD. The TLD Name server responds with the IP address of the DNS server that is authoritative for the specific domain name being queried. The resolver can then send the query directly to the authoritative DNS server for further processing.

TLD Name servers are critical components of the DNS infrastructure, as they enable the DNS to scale to the large number of domain names that exist on the internet. Without TLD Name servers, DNS queries would need to be sent to the authoritative DNS server for each individual domain name, which would be impractical given the size of the internet.

Authoritative DNS server

Authoritative Name server is the final authority in the process of DNS resolution. It stores all information about the domain names, including the IP address. The DNS recursor will find the IP address and will send it back to the user's computer, directing the user to the site.