Details of Domain Name System

Details of Domain Name System

The Domain Name System (DNS) is a fundamental component of the Internet that enables us to access websites, send emails, and perform various online activities. Despite its importance, DNS often remains a mystery to many. In this blog post, we will provide a high-level overview of how DNS works, shedding light on its key components and the process involved in translating human-friendly domain names into IP addresses.

  1. Understanding DNS and Its Purpose:
    DNS is essentially a distributed database that associates domain names (e.g., www.example.com) with their corresponding IP addresses (e.g., 192.0.2.1). It acts as a phonebook of the Internet, allowing us to use memorable domain names instead of remembering complex numerical IP addresses.

  2. DNS Components:
    a. DNS Resolver: When you type a domain name in your browser, the DNS resolver (typically provided by your ISP or network administrator) initiates the resolution process. It acts as the intermediary between your device and the DNS infrastructure.
    b. Root Servers: At the core of the DNS hierarchy are the root servers. They maintain a list of authoritative servers for top-level domains (TLDs) like .com, .org, and .net. There are a few hundred root servers distributed worldwide.
    c. TLD Name Servers: Each TLD, such as .com, has its own set of name servers. They maintain information about domain names registered under that TLD and provide referrals to the authoritative name servers for specific domains.
    d. Authoritative Name Servers: These servers hold the actual DNS records for individual domain names. Each domain typically has at least two authoritative name servers for redundancy and load balancing.

  3. DNS Resolution Process:
    a. Caching: The DNS resolver first checks its cache to see if it has a recent record of the requested domain name. If found, the resolver returns the corresponding IP address without further queries.
    b. Recursive Query: If the cache doesn’t contain the required record, the resolver starts a recursive query. It sends the request to one of the root servers, asking for the TLD name server responsible for the requested domain.
    c. TLD Name Server Resolution: The resolver then queries the TLD name server identified in the previous step. The TLD name server responds with the authoritative name servers for the specific domain.
    d. Authoritative Name Server Query: The resolver now sends a query to one of the authoritative name servers, requesting the IP address associated with the domain name.
    e. Response and Caching: The authoritative name server replies with the requested IP address. The resolver caches this response for future use and returns the IP address to the client device.

  4. TTL and DNS Caching:
    DNS caching is an important aspect that enhances the efficiency of the resolution process. DNS records have a Time To Live (TTL) value that specifies how long a resolver can keep a cached record before it needs to be refreshed. Short TTLs allow for more dynamic changes, while longer TTLs reduce the number of queries to authoritative name servers.