Chapter 4 - DNS (Domain Name System)

Introduction

The Domain Name System (DNS) is a critical component of the internet, responsible for translating human-readable domain names into IP addresses that computers use to identify each other on the network. This chapter covers the basics of DNS, including how it works and the different types of DNS records.

What is DNS?

DNS is often referred to as the "phone book of the internet." It enables users to access websites using easy-to-remember domain names instead of difficult-to-remember IP addresses.

Understanding how domain names are translated to IP addresses

When you type a domain name into your browser, the DNS system translates it into the corresponding IP address through a process called DNS resolution. Here's how it works:

• DNS Query: The browser sends a query to a DNS resolver to find the IP address associated with the domain name.

• Recursive Resolution: The DNS resolver queries multiple DNS servers, starting with the root DNS server, then the top-level domain (TLD) server (e.g., .com), and finally, the authoritative DNS server for the specific domain.

• Response: The authoritative DNS server responds with the IP address, which is then sent back to the browser.

• Connection: The browser connects to the web server using the IP address and loads the website.

DNS Records

DNS records are used to store various types of data about a domain. Each record type serves a different purpose.

Common record types: A, AAAA, CNAME

• A Record (Address Record): This maps a domain name to an IPv4 address. For example, the domain name example.com could be mapped to an IPv4 address 192.0.2.1.

• AAAA Record (IPv6 Address Record): This maps a domain name to an IPv6 address. For example, the domain name example.com could be mapped to an IPv6 address 2001:0db8:85a3:0000:0000:8a2e:0370:7334.

• CNAME Record (Canonical Name Record): This maps a domain name to another domain name, creating an alias. This is useful for pointing multiple subdomains to the same IP address indirectly. For example, the subdomain www.example.com could be mapped to another domain name, example.org. In this example, www.example.com is the alias, and example.org is the canonical name (or the target). The CNAME record essentially tells DNS resolvers that www.example.com should be resolved to the same IP address as example.org.

Conclusion

DNS is a foundational technology that makes the internet user-friendly by allowing the use of domain names instead of numerical IP addresses. Understanding DNS and its various record types is crucial for managing and troubleshooting network and domain-related issues.

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