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Understanding DNS and Its Functionality
Aug 10, 2024
Notes on DNS and How It Works
Introduction
Host: Piyush
Topic: Deep dive into DNS (Domain Name System)
Importance: Understanding DNS is crucial for developers, programmers, and cloud engineers.
What is DNS?
Full Form
: Domain Name System (or Domain Name Server)
Function
: Translates human-readable domain names (e.g., google.com) into IP addresses.
Analogy
: Just like you need an address to reach a house, computers need IP addresses to locate servers on the internet.
Reason for DNS
: Easier to remember domain names than numerical IP addresses.
How DNS Works
User Action
: User types a domain name (e.g., google.com) in a browser.
DNS Query
: The browser sends a request to a DNS server to resolve the domain name into an IP address.
DNS Resolution Process
:
The DNS server searches its records for the corresponding IP address.
Returns the IP address to the browser, which can then access the website.
DNS Caching
Purpose
: Reduce latency and load on DNS servers.
Levels of Caching
:
Browser Cache
: Stores recently accessed IP addresses.
Operating System Cache
: Further caching to improve performance.
Router Cache
: Local network caching.
ISP Cache
: Internet Service Provider caching.
Example
: If a user visits a site for the first time, a DNS query occurs. Subsequent visits might not require a new query due to caching.
Handling DNS Load
Challenge
: A single DNS server cannot handle billions of requests.
Solution
:
Decentralization
: Use multiple DNS servers to balance the load.
Root Name Servers
: 13 hard-coded servers that manage DNS queries.
Anycast Routing
: Internally route requests to the nearest available server.
DNS Record Types
1.
A Record
Points a domain to an IPv4 address.
2.
AAAA Record
Points a domain to an IPv6 address.
3.
CNAME Record
Allows a domain to point to another domain, effectively creating an alias.
Useful for pointing to external services (e.g., Vercel, Google) without worrying about IP changes.
4.
MX Record (Mail Exchange)
Used for directing email to mail servers.
5.
NS Record (Name Server)
Specifies which DNS server is authoritative for a domain.
6.
TXT Record
Used for adding text information related to the domain.
Important Files in DNS Troubleshooting
/etc/hosts
: Local DNS records for resolving domain names to specific IP addresses.
/etc/resolv.conf
: DNS settings file indicating which DNS servers to use.
Conclusion
Understanding DNS is essential for working in tech fields related to web development, networking, and cloud services.
The lecture emphasized the complexity and functionality of DNS, including the various record types and their uses.
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