Definition and Purpose of DNS

Introduction #

Understanding the Domain Name System (DNS) is fundamental to grasping how the internet operates. This documentation delves into the definition of DNS and its core purpose, providing a thorough comprehension of its role in facilitating web communication.

Definition of DNS #

DNS stands for Domain Name System. It is a hierarchical and decentralized system that translates human-readable domain names, such as example.com, into IP addresses, such as 192.0.2.1, which are used by computers to identify each other on the network. Essentially, DNS functions as the phonebook of the internet; humans can remember domain names easily, but computers and networking equipment communicate using IP addresses.

The Domain Name System comprises a network of DNS servers, which store and serve this information. A single piece of this information is called a DNS record, and there are different types of records for various purposes. For example, an “A” record usually points a domain name to an IPv4 address.

Purpose of DNS #

1. Human Readability #

One of the primary purposes of DNS is to enable humans to use easily understandable names to access websites and other resources on the internet. Remembering IP addresses, especially in IPv6 format, is impractical. DNS resolves this issue by allowing users to connect to resources using simple names.

2. Connection Establishment #

For communication to occur over the internet, devices must know each other’s IP addresses. DNS facilitates this by resolving domain names to IP addresses, which are essential for routing traffic over the internet.

3. Load Distribution #

DNS allows for the distribution of web traffic among a number of IP addresses through various techniques such as round-robin DNS. This is useful for load balancing and ensuring high availability and redundancy.

4. Service Discovery #

DNS is not just for websites; it’s an essential part of internet infrastructure. Various DNS record types enable service discovery. For example, MX records are used to route emails to the correct mail servers, and SRV records allow for the discovery of services such as SIP and XMPP.

5. Geographical Optimization #

Advanced DNS services can direct users to the nearest servers based on their geographic location, known as GeoDNS. This can significantly reduce latency and improve the performance of web services.

How DNS Works #

When you enter a URL in your browser, a series of steps are taken to resolve the domain name into an IP address:

1. Querying Local Cache: Your browser or operating system will check if it has a cached IP address for that domain name.
2. Request to Recursive DNS Servers: If not in the cache, your computer sends a request to a recursive DNS server, usually provided by your ISP.
3. Querying Root Name Servers: The recursive server queries a root name server if it doesn’t have the information cached.
4. Querying TLD Name Servers: The root server will direct the recursive server to a TLD (Top-Level Domain) server, such as .com or .org.
5. Querying Authoritative DNS Servers: The TLD server then directs the recursive server to the authoritative DNS server for the domain.
6. Retrieving the IP Address: The authoritative server provides the IP address to the recursive server, which then provides it to your browser.
7. Establishing Connection: Your browser uses this IP address to establish a connection to the web server and retrieve the webpage.