What is Domain Name System?

What is Domain Name System?

The Domain Name System (DNS) is a system that allows us to access websites and other internet resources using human-readable names instead of numerical addresses. DNS is often compared to a phone book of the internet, because it helps us find the right destination by translating names into numbers.

In this article, we will explain how DNS works, what are the main components of DNS, and why DNS is important for the internet.

How DNS Works

When we type a website name (also called a domain name) into a web browser, such as www.example.com, we expect to see the website content on our screen. But how does the browser know where to find the website? This is where DNS comes in.

DNS is a distributed database that stores information about domain names and their corresponding IP addresses. An IP address is a unique identifier for every device connected to the internet, such as 192.168.1.1 or 2400:cb00:2048:1::c629:d7a2. IP addresses are used by computers to communicate with each other, but they are not very user-friendly for humans.

DNS acts as a translator between domain names and IP addresses, so that we can use easy-to-remember names instead of complex numbers. DNS also provides other information about domain names, such as email servers, security certificates, and other services.

To understand how DNS translates domain names into IP addresses, let’s look at an example of a DNS query:

• We type www.example.com into our web browser and hit enter.
• The browser sends a request to a DNS resolver, which is a server that handles DNS queries from clients. The DNS resolver can be located within our internet service provider (ISP), or it can be a third-party service, such as 1.1.1.1 or 8.8.8.8.
• The DNS resolver checks its cache to see if it already has the IP address for www.example.com. If it does, it returns the IP address to the browser and the process is complete.
• If the DNS resolver does not have the IP address in its cache, it contacts a root nameserver, which is one of the 13 servers that store the information about the top-level domains (TLDs), such as .com, .org, .net, etc. The root nameserver returns the address of the TLD nameserver for .com to the DNS resolver.
• The DNS resolver contacts the TLD nameserver for .com and asks for the IP address of the authoritative nameserver for example.com. The authoritative nameserver is the server that has the final authority over the domain name and its associated records. The TLD nameserver returns the address of the authoritative nameserver for example.com to the DNS resolver.
• The DNS resolver contacts the authoritative nameserver for example.com and asks for the IP address of www.example.com. The authoritative nameserver returns the IP address of www.example.com to the DNS resolver.
• The DNS resolver caches the IP address of www.example.com and returns it to the browser.
• The browser uses the IP address to connect to the web server that hosts www.example.com and requests the website content.

This process may seem complicated, but it usually takes only a few milliseconds to complete. However, there are ways to optimize and speed up DNS queries, such as using caching, prefetching, load balancing, and security measures.

The Main Components of DNS

As we have seen in the previous section, there are four main types of servers involved in a DNS query:

• DNS resolver: A server that receives DNS queries from clients and resolves them by contacting other servers.
• Root nameserver: A server that stores information about the top-level domains and directs queries to the appropriate TLD nameservers.
• TLD nameserver: A server that stores information about a specific top-level domain and directs queries to the appropriate authoritative nameservers.
• Authoritative nameserver: A server that stores information about a specific domain name and its associated records.

In addition to these servers, there are also other components that make up the DNS system:

• Domain name: A human-readable name that identifies a website or other internet resource, such as www.example.com or mail.google.com.
• IP address: A numerical identifier that uniquely identifies a device connected to the internet, such as 192.168.1.1 or 2400:cb00:2048:1::c629:d7a2.
• DNS record: A piece of information that associates a domain name with an IP address or other data, such as an email server or a security certificate. There are different types of DNS records, such as A (address), AAAA (IPv6 address), MX (mail exchange), CNAME (canonical name), TXT (text), etc.
• DNS zone: A collection of DNS records for a specific domain name and its subdomains. For example, example.com and all its subdomains (such as www.example.com, blog.example.com, etc.) belong to the same DNS zone.
• DNS zone file: A text file that contains the DNS records for a DNS zone. A DNS zone file can be hosted on one or more authoritative nameservers.
• DNS delegation: The process of transferring the authority over a subdomain to another nameserver. For example, if example.com delegates the subdomain blog.example.com to another nameserver, then that nameserver becomes the authoritative nameserver for blog.example.com and its subdomains.

Why DNS is Important for the Internet

DNS is an essential component of the internet, because it enables us to access websites and other online services using simple and memorable names instead of complex and obscure numbers. Without DNS, we would have to memorize or write down the IP addresses of every website we want to visit, which would be very inconvenient and error-prone.

DNS also provides other benefits for the internet, such as:

• Scalability: DNS is a distributed and hierarchical system that can handle billions of domain names and IP addresses without a single point of failure or bottleneck.
• Flexibility: DNS allows us to change the IP address or location of a website or service without affecting its domain name, which makes it easier to migrate, update, or load balance servers.
• Security: DNS can help protect us from malicious attacks, such as phishing, malware, or denial-of-service, by verifying the identity and authenticity of websites and services using security certificates and other mechanisms.
• Performance: DNS can help improve the speed and reliability of our internet experience by caching, prefetching, and optimizing DNS queries and responses.

Conclusion

DNS is a system that translates domain names into IP addresses so that we can access websites and other internet resources using human-readable names instead of numerical addresses. DNS is often compared to a phone book of the internet, because it helps us find the right destination by translating names into numbers.

DNS works by sending queries from clients to servers until the IP address of the requested domain name is found. There are four main types of servers involved in a DNS query: DNS resolver, root nameserver, TLD nameserver, and authoritative nameserver.

DNS also has other components, such as domain name, IP address, DNS record, DNS zone, DNS zone file, and DNS delegation. These components help store, manage, and update information about domain names and their associated data.

DNS is important for the internet, because it enables us to access websites and services using simple and memorable names instead of complex and obscure numbers. DNS also provides other benefits for the internet, such as scalability, flexibility, security, and performance.

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