DNS Magic and Internals
What is DNS and Why is it Important?
The Domain Name System (DNS) is like the Internet’s phonebook.It translates human-friendly domain names (e.g., google.com) into machine-readable IP addresses (e.g., 142.250.74.206).
Think of DNS as a contact list in your phone. Instead of remembering every friend’s phone number, you simply tap their name, and your phone dials the right number. Similarly, DNS helps your browser find the IP address (number) of a website based on its name.
How Does DNS Work?
User Request: When you type a domain name into your web browser, the browser sends a query to a DNS server to resolve (translate) the domain into its corresponding IP address.
DNS Resolver: The DNS server (resolver) follows a structured process, querying other servers like root servers, TLD servers (e.g., .com, .net), and authoritative name servers to find the IP address.
Response: Once the IP address is found, it is sent back to your browser, which then connects to the website’s server to load the content.
Why is DNS Important?
User-Friendly Browsing:
DNS eliminates the need to memorize complex IP addresses, making the internet more accessible for everyone.
Efficient Connectivity:
DNS allows devices worldwide to communicate seamlessly, regardless of geographic location.
Scalability:
The hierarchical structure of DNS ensures it can handle the vast number of websites and devices connected to the internet.
Redundancy and Reliability:
DNS uses a distributed system of servers, ensuring uninterrupted connectivity even if one server fails.
Security:
Modern DNS implementations support protocols like DNSSEC (Domain Name System Security Extensions) to protect against attacks like spoofing.
Type of DNS Records
DNS records are building blocks of the Domain Name System (DNS).Each record serves a specific purpose to ensure smooth communication between browsers, servers, and other Internet-connected devices.DNS records play a crucial role in ensuring the functionality, reliability, and security of the internet. Each record type has a specific job, collectively enabling websites, emails, and services to work seamlessly.
A Record (Address Record)
Purpose: Maps a domain name to an IPv4 address.
Example: example.com → 192.168.1.1
Use case: Directs traffic to a specific server hosting a website.
AAAA Record (IPv6 Address Record)
Purpose: Maps a domain name to an IPV6 address.
Example: example.com → 2607:f8b0:4005:805::200e
Use case: Supports modern networking by handling IPv6 addresses.
CNAME Record (Canonical Name Record)
Purpose: Aliases one domain name to another.
Example: example.com → example.com
Use case: Redirects subdomains or aliases to the main domain.
MX Record (Mail Exchange Record)
Purpose: Specifies the mail server responsible for receiving email for the domain.
Example: example.com → mail.example.com
Use case: Ensures email is routed to the correct server.
TXT Record (Text Record)
Purpose: Stores human-readable text or verification data.
Example: SPF (Sender Policy Framework) or DKIM (DomainKeys Identified Mail) entries.
Use case: Verifies domain ownership, email authentication, or other metadata.
NS Record (Name Server Record)
Purpose: Indicates the authoritative DNS servers for a domain.
Example: example.com → ns1.examplehost.com
Use case: Delegates responsibility for managing DNS to specific name servers.
SOA Record (Start of Authority Record)
Purpose: Contains administrative information about the domain, including the primary DNS server and zone serial number.
Example: Identifies the authoritative name server for the domain.
Use case: Establishes authority and settings for the domain’s DNS zone.
PTR Record (Pointer Record)
Purpose: Maps an IP address to a domain name (reverse of an A or AAAA record).
Example: 192.168.1.1 → example.com
Use case: Used for reverse DNS lookups, often in email server verification.
SRV Record (Service Record)
Purpose: Specifies services and ports for a domain.
Example: _sip._tcp.example.com → server1.example.com.5060
Use case: Used for VoIP, messaging, and other network services.
DNSSEC Record (DNS Security Extensions)
Purpose: Enhance DNS security by verifying the authenticity of DNS responses.
Types: DS, RPSIG, NSEC, DNSKEY
Use case: Protect against DNS spoofing and other attacks.
ALIAS Record
Purpose: Points a domain to another domain name at the root level.
Example: example.com → example.com
Use case: Useful for redirecting apex domains where CNAME records are not allowed.
HINFO Record (Host Information Record)
Purpose: Provides information about a server \ u2019s hardware and operating system.
Example: example.com → Intel i7, Linux
Use case: Rarely used, primarily for troubleshooting.
DNS Hierarchy : From Root to Authoritative Servers
The DNS hierarchy is a structured and distributed system designed to efficiently resolve domain names into IP addresses. It follows a top-down approach starting from the root servers and ending at the authoritative name servers.
The hierarchical structure ensures efficiency, scalability, and fault tolerance. Each level in the hierarchy has a specific function, reducing the load on individual servers.
Root Servers
The root servers are the top-most level of the DNS hierarchy. They do not store specific domain records but provide references to the appropriate Top-Level Domain (TLD) servers. There are 13 sets of root servers, operated by organizations worldwide.
Example: if the domain is chaicode.com, the root server directs the query to the .com TLD servers.
Top-Level Domain (TLD) Servers
The servers manage specific domain extensions, such as .com, .org, .net, or country codes like .in and .uk. They provide the location of the authoritative name servers for the requested domain.
Example: For chaicode.com, the TLD servers for .com are queried.
Authoritative Name Servers
These servers store the actual DNS records (e.g., A, CNAME, MX) for a specific domain. They return the final response to the DNS resolver, enabling it to connect the browser to the correct server.
Example: For chaicode.com, the authoritative name server holds the IP address associated with chaicode.com.
How The Hierarchy Works: A step-by-step Example
Imagine you type chaicode.com in your browser:
Your browser sends a query to a recursive resolver (managed by your ISP or a public DNS service like Google DNS or Cloudflare).
The recursive resolver queries a root server. The root server identifies the TLD .com and directs the resolver to the appropriate .com TLD server.
The resolver contacts the .com TLD server. The TLD server identifies the authoritative name server for chaicode.com.
The resolver queries the authoritative name server for chaicode.com, which provides the IP address of the domain (e.g., 93.184.216.34)
The resolver returns the IP address to your browser, which uses it to establish a connection to the web server hosting chaicode.com.
Server - Client Architecture
Client-Side vs Server-Side : A comprehensive guide for beginners
To understand the difference between client-side and server-side, think of it as two halves working together to display a website or application.
Client-Side: It happens on the user’s device, like a browser or mobile app. It handles what the user sees and interacts with on the front end.
Think of it as a restaurant menu you hold in your hands. The menu lets you choose what you want to see or order.
Example: The browser displays a login form. When you type a password, the client-side JavaScript checks if it meets basic rules.
Server-Side: It happens on a remote server (the backend) that processes data, stores information, and sends the requested content to the client.
In a restaurant, the server-side is like the kitchen where chefs prepare your order after you select it from the menu.
Example: Once you submit the form, the server-side checks the username and password against its database. If the credentials are correct, it sends a response back.
Web Server and Hosting: How Your Website Becomes Accessible to the World
When you create a website, making it accessible to everyone involves a combination of web servers and web hosting. Web servers and hosting work together to make your website available worldwide. Hosting provides the space to store your website, while the web server ensures it can respond to user requests, allowing your site to be seen by anyone with internet access.
Web Server
A web server is a computer that stores your website files (like HTML, images, and videos) and delivers them to users when they visit your website. It does this using protocols like HTTP/HTTPS.
Web Hosting
Web hosting is a service that provides space on a server to store your website files and make them accessible on the internet. Hosting companies maintain these servers and ensure they’re online 24/7.
How Does a Website Become Accessible?
Domain Name Registration: You register a domain name. This name is linked to the IP address of the hosting server using DNS.
Website Files Uploaded to Hosting Server: Your files (HTML, CSS, JavaScript, etc.) are uploaded to the hosting server using tools like cPanel or FTP.
User Sends a Request: A user types your domain name in their browser. DNS translates the domain name to the hosting server’s IP address.
Server Responds: The server receives the request, fetches the appropriate files, and sends them to the user’s browser.
Website Displayed: The browser renders the website based on the files and code it receives.
Conclusion
DNS and client-server architecture work together to make the internet functional and user-friendly. DNS translates domain names into IP addresses, while the client-server model handles the communication between your device (client) and the server to deliver data. Together, they ensure users can access websites and services quickly, reliably, and efficiently.