How the Internet Works — HTTP, TCP/IP

What Happens When You Type a URL

When you type https://techpaths.dev and press Enter, a lot happens in under 200ms:

The Network Layers

The internet is built on layers. Each layer has a specific job and talks to the layers above and below it.

As a developer, you mostly work with the top two layers — Application and Transport.

IP — Internet Protocol

Every device on the internet has an IP address — a unique identifier.

IPv4: 192.168.1.1    (32-bit, ~4 billion addresses)
IPv6: 2001:db8::1    (128-bit, virtually unlimited)

IP handles routing — getting packets from source to destination across multiple networks. Each router along the path forwards the packet closer to the destination.

TCP — Transmission Control Protocol

TCP provides reliable, ordered delivery of data.

The Three-Way Handshake

Client → Server: SYN (I want to connect)
Server → Client: SYN-ACK (OK, I'm ready)
Client → Server: ACK (Great, let's go)

Why TCP is Reliable

Acknowledgments — receiver confirms every packet received
Retransmission — sender resends lost packets
Ordering — packets arrive in the right order
Flow control — don't overwhelm the receiver

TCP vs UDP

	TCP	UDP
Reliability	Guaranteed delivery	Best effort
Order	Ordered	Unordered
Speed	Slower (overhead)	Faster
Use case	HTTP, email, file transfer	Video streaming, gaming, DNS

UDP is used when speed matters more than reliability — a dropped video frame is better than waiting for retransmission.

HTTP — HyperText Transfer Protocol

HTTP is the language browsers and servers use to communicate. It runs on top of TCP.

Request Structure

GET /blog/cap-theorem HTTP/1.1
Host: techpaths.dev
Accept: text/html
Cookie: session=abc123
User-Agent: Mozilla/5.0

Response Structure

HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: 12345
Cache-Control: max-age=3600
 
<!DOCTYPE html>
<html>...

HTTP Methods

Method	Purpose	Body
GET	Retrieve data	No
POST	Create data	Yes
PUT	Replace data	Yes
PATCH	Update data	Yes
DELETE	Delete data	No

HTTP Status Codes

Range	Meaning	Examples
2xx	Success	200 OK, 201 Created
3xx	Redirect	301 Moved, 304 Not Modified
4xx	Client error	400 Bad Request, 401 Unauthorized, 404 Not Found
5xx	Server error	500 Internal Error, 503 Service Unavailable

HTTPS — HTTP + TLS

HTTPS adds encryption via TLS (Transport Layer Security).

Why HTTPS matters:

Confidentiality — nobody can read your data in transit
Integrity — data can't be tampered with
Authentication — you're talking to the real server, not an imposter

HTTP/1.1 vs HTTP/2 vs HTTP/3

HTTP/2 is now standard. HTTP/3 is being adopted — Cloudflare and Google support it.

DNS — Domain Name System

DNS translates domain names to IP addresses. We covered this in depth in the DNS article — the key points:

Browser checks cache → OS cache → Recursive resolver → Root → TLD → Authoritative
TTL controls how long results are cached
GeoDNS routes users to nearest server

Latency by Network Hop

Hop	Typical latency
Same machine	~0.1ms
Same data center	~0.5ms
Same city	~1-5ms
Same country	~10-30ms
Cross-continent	~100-200ms

This is why CDNs exist — serve content from the nearest edge node to minimize hops.

Key Takeaway

Every request: DNS lookup → TCP handshake → TLS handshake → HTTP request → response
IP routes packets across networks
TCP ensures reliable, ordered delivery
HTTP is the application protocol for web communication
HTTPS = HTTP + TLS encryption — always use it
HTTP/2 multiplexes multiple requests over one connection — much faster than HTTP/1.1