Domain Name System (DNS): From Basic to Advanced
Have you ever wondered what happens when you type a website address like "google.com" into your browser and press Enter? How does your browser know exactly which server to connect to in order to load that website? The answer lies in the Domain Name System, or DNS.
What is DNS?
DNS (Domain Name System) is a hierarchical, distributed system used to convert easy-to-remember domain names (e.g., google.com) into numeric IP addresses (e.g., 142.250.180.142) that computers use to locate servers on the internet. Think of DNS as a giant phone book for the internet. Instead of having to remember complicated IP numbers, you just need to remember an easy-to-remember domain name, and DNS will "translate" that domain name into the corresponding IP address.
Example: You want to call your friend named Lan. Instead of having to remember Lan's long phone number, you can just look up "Lan" in your phone's contacts. The contacts will tell you Lan's phone number, and you can call Lan easily. DNS works in a similar way.
Why Do We Need DNS?
The main reason is because it is easier for humans to remember names than numbers. Imagine having to remember hundreds of different IP addresses for all the websites you visit regularly. That would be difficult and time-consuming. DNS helps us solve this problem by providing an easy way to access websites and online services.
In addition, DNS also helps:
- Easy IP address updates: When a website moves to a new server with a different IP address, DNS allows domain name records to be updated to point to the new IP address without the user having to change anything.
- Traffic Distribution: DNS can be used to distribute traffic to multiple servers, improving website performance and load capacity.
- Providing other services: DNS is also used for many other purposes, such as email routing and identity authentication.
How DNS Works
The process of domain name resolution (i.e. converting a domain name to an IP address) involves many steps, and involves many different types of DNS servers.
- Domain name resolution request: When you type a domain name into your browser (for example, "example.com"), your browser sends a domain name resolution request to a DNS server configured on your computer (usually a DNS server provided by your internet service provider (ISP). This DNS server is called a DNS Resolver .
- Cache Check: The DNS Resolver will check to see if it already has a record for that domain name in its cache. If it does, it will return the corresponding IP address to the browser. This speeds up the name resolution process because it does not need to perform the next steps.
- Querying the Root DNS Server: If the DNS Resolver does not have the record in its cache, it queries one of the 13 Root DNS Servers on the internet. These Root DNS Servers know the addresses of the Top-Level Domain (TLD) DNS Servers.
- Query Top-Level Domain (TLD) Server: The DNS Resolver queries the TLD Server that corresponds to the domain name extension (e.g. ".com", ".org", ".net"). This TLD Server knows the address of the Authoritative DNS Server for that domain.
- Query Authoritative DNS Server: The DNS Resolver will query the Authoritative DNS Server(ex: Hostinger) for the domain name. This server contains the authoritative information about the domain name, including the corresponding IP address.
- Return IP Address: The Authoritative DNS Server will return the IP address to the DNS Resolver.
- Caching: The DNS Resolver will cache the IP address for future domain name resolution requests. The cache duration (TTL - Time To Live) is determined by the Authoritative DNS Server.
- Connecting to the web server: Your browser uses the IP address received to connect to the web server and download the web page.
For example, when you visit "example.com", the DNS resolution process might go like this:
- Your browser sends a request to your ISP's DNS Resolver.
- DNS Resolver checked cache but found no information.
- The DNS Resolver queries a Root Server to find the address of the ".com" TLD server.
- Root Server returns the address of the ".com" TLD server.
- The DNS Resolver queries the ".com" TLD server to find the address of the Authoritative DNS server for "example.com".
- The ".com" TLD server returns the address of the Authoritative DNS server for "example.com".
- The DNS Resolver queries the Authoritative DNS server for "example.com" to find the IP address.
- The Authoritative DNS server for "example.com" returns an IP address (e.g. 93.184.216.34).
- DNS Resolver caches the IP address and returns it to your browser.
- Your browser uses the IP address to connect to the web server of "example.com".
Important DNS Record Types
Authoritative DNS servers store information about domain names in the form of records (DNS records). Some common types of DNS records include:
- A Record: An A record maps a domain name to an IPv4 address.
- AAAA Record: The AAAA record (Quad-A record) maps a domain name to an IPv6 address.
- CNAME Record: A CNAME (Canonical Name record) creates an alias for another domain name. For example, "www.example.com" could be a CNAME pointing to "example.com".
- MX Record: The MX (Mail Exchange record) specifies which email server is responsible for receiving email for a domain name.
- TXT Record: A TXT record contains arbitrary text and is often used for authentication purposes, such as verifying domain ownership.
- NS Record: The NS (Name Server record) specifies the authoritative DNS servers for a domain name.
DNS Checker Tool
There are many online tools and apps that allow you to check a domain name's DNS information. Some popular tools include:
These tools allow you to view a domain's different DNS records, test DNS server response times, and identify DNS configuration issues.
Conclude
DNS is an important part of the internet, allowing us to access websites and online services easily and efficiently. Understanding how DNS works can help you solve problems related to internet connectivity and website security. Hopefully this article has given you an overview of DNS, from the basics to more advanced aspects.
