What Does Domain Name System (DNS) Mean?

The Domain Name System (DNS) is a decentralized naming system that maps domain names to IP addresses and other resource records. DNS enables the translation of human-friendly domain names, such as www.example.com, into numerical IP addresses that computers use to identify each other on the Internet.

When a user types a domain name into their web browser, the browser sends a query to a DNS resolver, which then looks up the IP address associated with that domain name and returns it to the browser. This allows users to access websites, send emails, and perform other Internet activities using easy-to-remember domain names, rather than having to remember numerical IP addresses. The DNS system is hierarchical, with different levels of domains and subdomains, and is managed by various organizations, including domain registrars, Internet service providers, and top-level domain registries.

Dissecting Domain Name System (DNS)

The DNS was developed in the 1980s as a replacement for the earlier ARPANET host table system, which was a centralized system for mapping host names to network addresses. The host table system became impractical as the Internet grew in size and complexity, and a more scalable and distributed system was needed.

The development of the DNS began in 1983, when Paul Mockapetris and Jon Postel of the University of Southern California's Information Sciences Institute (ISI) proposed a new domain name system that would allow for distributed and hierarchical name resolution. The first implementation of the DNS was deployed in 1984, and it quickly became the standard naming system for the Internet.

The DNS has undergone several revisions and enhancements since to improve its scalability, security, and performance.

DNS Structure

The Domain Name System (DNS) is a distributed database that stores information about domain names and their corresponding IP addresses. The DNS is organized into a hierarchical structure, with each level having specific functions and responsibilities.

Root Domain

At the top of the hierarchy is the root domain, represented by a dot (.), which contains information about the top-level domains (TLDs) such as .com, .org, .net, and so on. The root domain is managed by the Internet Assigned Numbers Authority (IANA) and is served by a network of 13 root DNS servers distributed globally.

Top-Level Domains

TLDs are the next level of the DNS hierarchy and are represented by the suffixes at the end of domain names, such as .com, .org, .edu, etc. There are two types of TLDs: generic TLDs (gTLDs) and country-code TLDs (ccTLDs). Each TLD is managed by a separate organization or entity and is responsible for maintaining information about the second-level domains within that TLD.

Second-Level Domains

Below the TLDs are the second-level domains (SLDs), which are registered by individuals or organizations. For example, "example" is an SLD in the domain name www.example.com. Each SLD is managed by the organization or individual that registered the domain name and can have its own set of authoritative name servers that store information about the subdomains and other resources within that SLD.

Subdomains

Subdomains are additional levels of the DNS hierarchy that are located below the SLDs. They are used to further divide the domain name into smaller, more specific parts, such as mail.google.com, drive.google.com, etc. Each subdomain is managed by the organization or individual that registered the domain name and is responsible for maintaining information about the DNS records for that subdomain.

When a client computer or device wants to resolve a domain name, it sends a query to a DNS resolver, which is typically provided by the user's Internet service provider (ISP). The DNS resolver sends the query to a series of authoritative name servers, starting from the root domain and moving down the hierarchy until it finds the IP address associated with the requested domain name.

DNS Resolution Process and DNS Records

The Domain Name System is a hierarchical and distributed naming system that is used to translate domain names into IP addresses, which computers use to identify each other on the internet. Here are the basic components that make the DNS work:

1. DNS Resolution Process: When a user enters a domain name into their web browser, the browser first checks its local cache to see if it already has the corresponding IP address. If it doesn't have the IP address, the browser sends a DNS query to the user's local DNS resolver, which is typically provided by the user's Internet Service Provider (ISP).
2. Recursive DNS Resolution: The local DNS resolver then performs a recursive DNS resolution process. It sends a request to the root DNS server to ask for the authoritative DNS server for the top-level domain of the requested domain name. The root DNS server responds with the IP addresses of the TLD DNS servers for that domain.
3. Iterative DNS Resolution: After the local DNS resolver receives a response from the root DNS server with the IP addresses of the TLD DNS servers for the requested domain name, it sends a request to one of those TLD DNS servers, requesting the IP address of the authoritative DNS server responsible for managing the second-level domain of the requested domain name. The TLD DNS server then responds with the IP address of the authoritative DNS server for that domain.
4. Authoritative DNS Resolution: The local DNS resolver then sends a request to the authoritative DNS server for the second-level domain, asking for the IP address of the domain name that was originally requested. The authoritative DNS server responds with the IP address, which is then cached by the local DNS resolver and returned to the user's web browser.
5. DNS Caching: Once the local DNS resolver has obtained the IP address for a domain name, it caches the information for a period of time specified by the Time-To-Live (TTL) value in the DNS record. This reduces the number of DNS queries needed for frequently accessed domain names and improves the overall performance of the DNS system.
6. DNS Records: DNS records are used to store information about domain names and their corresponding IP addresses. There are several types of DNS records, including A records (which map a domain name to an IPv4 address), AAAA records (which map a domain name to an IPv6 address), MX records (which specify the mail exchange server for a domain), and CNAME records (which specify an alias for a domain name).