Today’s lesson goal: Understand the fundamental principles of the Domain Name System (DNS) and its role in internet connectivity.
The Domain Name System, commonly referred to as DNS, is the phonebook of the internet. When we use a web browser to visit a website, we usually type a domain name like “google.com”. However, web browsers interact over the Internet using IP addresses. DNS translates these domain names into IP addresses, allowing browsers to load internet resources.
How DNS Works:
- DNS Query: When you type a domain name in your browser, your computer sends a DNS query to your local DNS server, typically provided by your ISP (Internet Service Provider).
- Recursive Resolution: The local DNS server then acts on your behalf and queries other DNS servers across the internet. It starts at the root DNS servers, goes to the TLD (Top-Level Domain) servers (like .com, .org), and ends at the authoritative DNS servers for the domain you’re querying.
- Retrieving the IP Address: The authoritative DNS server contains the actual IP address and other records for the domain. Once retrieved, it is passed back through the chain to your computer.
- Caching: To speed up future requests to the same domain, DNS servers cache the results for a certain period, known as the TTL (Time to Live).
Types of DNS Records:
- A Record: Maps a domain name to an IPv4 address.
- AAAA Record: Maps a domain name to an IPv6 address.
- CNAME Record: Maps a domain name to another domain name (alias).
- MX Record: Specifies mail exchange servers for a domain.
- NS Record: Indicates the authoritative DNS servers for a domain.
- TXT Record: Allows text to be stored in a DNS record, often used for verification purposes.
DNS Security: With its critical role, DNS faces various security threats like DNS spoofing or cache poisoning, where attackers redirect traffic to malicious sites. DNSSEC (DNS Security Extensions) adds a layer of security by enabling DNS responses to be digitally signed, thus verifying their authenticity.
For a deeper understanding, you can watch this explanatory video: What is DNS?.
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