Networking Basics - System Design Course

When a browser sends a request to a server, the server processes it and returns a response—typically HTML, CSS, or JavaScript files. HTTP is stateless, meaning each request is treated as independent, with no memory of previous interactions.

Key Features of HTTP:

Data is sent as plain text.
Uses port 80 by default.
No encryption or authentication.
Best suited for non-sensitive content.

Disadvantages:

Vulnerable to data interception and tampering.
Not secure for login or payment information.
Doesn’t meet modern privacy standards.

What is HTTPS?

HTTPS is the secure version of HTTP, adding encryption using SSL/TLS to ensure data confidentiality, integrity, and authenticity during communication between browser and server.

How HTTPS Works:

Before data transmission, the client and server establish a secure SSL/TLS handshake. This process ensures that all subsequent data is encrypted, preventing third parties from accessing or altering it.

Key Features of HTTPS:

Encrypts all transferred data.
Uses port 443.
Requires an SSL/TLS certificate.
Preferred by search engines for security.

Benefits of HTTPS:

Protects sensitive user data like passwords and payment details.
Displays a padlock icon in the browser address bar, increasing user trust.
Helps meet compliance requirements such as GDPR or PCI-DSS.
Enables advanced features like HTTP/2 and service workers.

Summary Comparison

Feature	HTTP	HTTPS
Encryption	No	Yes (SSL/TLS)
Port	80	443
Certificate	Not required	SSL/TLS required
Data Protection	None	Encrypted and secure
Suitable For	Public or static content	Secure transactions, user data
SEO Advantage	None	Yes

DNS, CDN, and reverse proxies

What is DNS?

The Domain Name System (DNS) translates human-readable domain names (like example.com) into IP addresses that computers use to identify each other on the network.

How DNS Works:

When a user types a URL into a browser, the DNS resolver queries various DNS servers to find the IP address of the requested domain, allowing the browser to load the website.

Key Functions of DNS:

Maps domain names to IP addresses.
Helps route internet traffic efficiently.
Supports load balancing and redundancy via multiple records.
Essential for navigating the web using domain names.

What is a CDN?

A Content Delivery Network is a system of distributed servers that deliver content to users based on their geographic location, improving load times and performance.

How a CDN Works:

When a user requests content, the CDN delivers it from the nearest edge server instead of the origin server, reducing latency and bandwidth consumption.

Benefits of Using a CDN:

Faster content delivery across regions.
Reduced server load and bandwidth costs.
Improved website uptime and reliability.
Better user experience and SEO performance.

What is a Reverse Proxy?

A reverse proxy is a server that sits between client devices and a web server, forwarding client requests to the appropriate backend server and returning the response to the client.

How Reverse Proxies Work:

They receive incoming requests, route them to the correct backend server, and send the server’s response back to the client—often used for load balancing, caching, and security.

Advantages of Reverse Proxies:

Load balancing between multiple servers.
SSL termination and centralized security controls.
Caching static content to reduce backend load.
Protects server identity and internal architecture.

WebSockets and REST APIs

What is a REST API?

A REST API is an architectural style for designing networked applications that use HTTP methods (GET, POST, PUT, DELETE) to interact with resources represented in formats like JSON or XML.

How REST APIs Work:

Clients send requests to specific endpoints (URLs), and the server responds with data or status updates. Each request is independent, and the server does not store client context between calls (stateless).

Key Features of REST APIs:

Stateless communication for scalability.
Resource-based structure using URIs.
Standardized HTTP methods.
Supports caching and layered architecture.

Use Cases:

Web and mobile app backends.
Integrating third-party services.
CRUD operations for databases.

What is WebSocket?

WebSocket is a communication protocol that provides full-duplex, persistent connections between a client and a server, enabling real-time data exchange.

How WebSockets Work:

Once a WebSocket connection is established via an HTTP handshake, it stays open, allowing both client and server to send data at any time without repeated requests.

Key Features of WebSockets:

Bi-directional, real-time communication.
Reduces overhead by avoiding repeated HTTP requests.
Low latency and efficient for live updates.
Ideal for continuous data streams.