DNS Components and How DNS Resolution Works

DNS Components

What are DNS Components?

The Domain Name System works through several coordinated components. These components form a distributed system that translates domain names into IP addresses. The main parts include the DNS hierarchy, DNS name servers, and the navigation process used during DNS resolution.

1. DNS Hierarchy

DNS follows a hierarchical structure that organizes domain names into levels. A domain name usually contains two or more labels separated by dots. The label on the far right represents the top level domain. Each label to the left represents a subdivision or subdomain of the domain above it.

dns-components-and-how-dns-resolution-works-3

For example, in the domain www.nerdstudyhub.com, the structure begins with the root, followed by the top level domain .com, then the domain nerdstudyhub, and finally the hostname www.

The Domain Name System is built on a hierarchy of DNS servers. The hierarchy of authoritative DNS servers mirrors the hierarchy of domains. Each level of the structure is responsible for directing queries to the next appropriate server until the requested domain information is found.

2. DNS Name Servers

DNS relies on several types of servers that work together to resolve domain names. At the top of the hierarchy are the root name servers. These servers are responsible for directing queries toward the correct top level domain servers when a request begins.

dns-components-and-how-dns-resolution-works-4

Every domain or subdomain has one or more authoritative DNS servers. These servers publish the official DNS records for a domain and also provide information about name servers responsible for any subdomains beneath them.

DNS servers fall into four main categories.

Recursive resolvers handle requests from users and perform the necessary queries to find the correct IP address.
Root name servers sit at the highest level of the DNS hierarchy and guide requests toward the appropriate top level domain servers.
TLD name servers store information about domains within specific top level domains such as .com, .org, or .net.
Authoritative name servers contain the final DNS records for a domain and provide the actual IP address associated with a hostname.

In a typical DNS lookup without cached data, these servers cooperate to find and return the correct IP address to the client.

3. Root Servers

Root servers form the foundation of the DNS name server hierarchy. They maintain information about the authoritative name servers responsible for each top level domain.

Root servers may not store the final DNS record for a domain, but they know which server is responsible for it. When a query reaches a root server, the server directs the request to the appropriate top level domain server.

These servers are operated by organizations contracted by the Internet Corporation for Assigned Names and Numbers and other major institutions. More details about these servers are available at https://root-servers.org/.

3.1 Authoritative Servers

Authoritative name servers store the official DNS records for a domain. When a domain is registered, information about its authoritative servers is added to the DNS system.

dns-components-and-how-dns-resolution-works-5

These servers respond with the final answer when a query requests the IP address for a specific domain or host. Many DNS systems use both primary and secondary authoritative servers to ensure reliability and redundancy.

3.2 Local Name Servers

Local name servers, sometimes called caching servers, store DNS responses temporarily. When a client makes a DNS request, the local server checks its cache first. If the requested information is already stored, the server returns the answer immediately.

Caching significantly speeds up DNS queries within a network. It reduces the need to contact authoritative servers repeatedly for the same domain names.

4. DNS Navigation Process

DNS navigation describes how a query travels through different servers to resolve a domain name. Two main navigation methods are used: iterative queries and recursive queries.

4.1 Iterative Query

In an iterative query, the client contacts multiple DNS servers one by one. The client first sends a request to the initial server. If that server does not have the requested record, it responds with the address of another server that may know the answer.

The client then sends the query to the next server. This process continues until a server returns the final IP address. In this method, the client is responsible for contacting each server until the domain name is resolved.

4.2 Recursive Query

In a recursive query, the client sends a request to the first DNS server and waits for a final response. If the server does not know the answer, it forwards the request to another DNS server on behalf of the client.

The process continues between servers until the authoritative server returns the correct IP address. The first server then sends the final response back to the client. In this case, the client sends only one request and the DNS servers handle the rest of the resolution process..

Name Server Records Example

www.nerdstudyhub.com NS ns1.domaininnepal.com
www.nerdstudyhub.com NS ns2.domaininnepal.com
www.nerdstudyhub.com NS ns3.domaininnepal.com
www.nerdstudyhub.com NS ns4.domaininnepal.com

These records tell DNS servers where to find information about the domain and how requests should be handled.

5. DNS Records

DNS records define how domain names are mapped and how services like email or subdomains work. These records are stored in authoritative servers.

The most common DNS records include:

A record maps a domain name to an IP address.
MX record defines where emails for a domain should be delivered.
CNAME record redirects one domain or subdomain to another.
TXT record stores text-based data such as verification or security information.
PTR record maps an IP address back to a domain name.

Example DNS Records for nerdstudyhub.com

Here is how DNS records look in practice:

nerdstudyhub.com A 209.42.27.15
nerdstudyhub.com NS ns1.domaininnepal.com
nerdstudyhub.com NS ns2.domaininnepal.com
nerdstudyhub.com NS ns3.domaininnepal.com
nerdstudyhub.com NS ns4.domaininnepal.com
nerdstudyhub.com MX nerdstudyhub.com

www.nerdstudyhub.com A 209.42.27.15
www.nerdstudyhub.com CNAME nerdstudyhub.com
www.nerdstudyhub.com MX nerdstudyhub.com