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Network//Lesson 01

Networking

30 min·theory

Networking

🎯 After reading this lesson

By the end of this lesson, you will be able to confidently do the following 3 things.

  • ▸✅ TCP/IP (Transmission Control Protocol / Internet Protocol — the foundational rules of internet communication) — what it is and why it underlies all communication
  • ▸✅ HTTP/HTTPS (HyperText Transfer Protocol — the protocol for sending and receiving web pages; S is the encrypted version) — a perennial interview favorite
  • ▸✅ Protocol (protocol — a set of communication rules computers agree to follow) — how the flow actually works

Keep the learning objectives as a checklist, and close the lesson only once you can answer all of them.

🌐 The People Who Built the Internet — 5 People, 5 Panels

01
Vint CerfVint Cerf
Co-creator of TCP/IPDARPA → MCI → Google (Chief Internet Evangelist)1943~Present

'Father of the Internet' — the person who connected the entire world into a single network 50 years ago with TCP/IP

  • 1973 Co-designed the TCP/IP protocol draft with Bob Kahn — the paper 'A Protocol for Packet Network Intercommunication'
  • 1983 ARPANET officially migrated to TCP/IP — the birth of the modern Internet
  • 1997 Received the National Medal of Technology
  • 2004 Shared the Turing Award with Bob Kahn. Currently a VP at Google, working on Internet governance
TCP/IP — the foundational protocol of all internet communicationTCP/IP · Father of the Internet
02
Bob KahnBob Kahn
Co-creator of TCP/IPDARPA → CNRI1938~Present

Architect of packet-switching networks — if Cerf is 'IP', Kahn is the brain behind 'TCP'

  • 1972 Led the first public demonstration of ARPANET — proved packet switching at the ICCC conference
  • 1973 Co-designed TCP/IP with Vint Cerf — established the End-to-End principle
  • 1986 Founded CNRI (Corporation for National Research Initiatives)
  • 2004 Shared the Turing Award with Cerf + received the 2005 U.S. Presidential Medal of Freedom
The End-to-End principle and TCP — the reason the internet works 'reliably'TCP/IP · Packet Switching Designer
03
Paul MockapetrisPaul Mockapetris
Creator of DNSUSC ISI → Nominum1948~Present

The person who invented domain names — the reason you can type codemaster40.com

  • 1983 Authored RFC 882 and 883 — published the first DNS system specification
  • 1984 Personally developed the first DNS implementation, 'JEEVES'
  • 1987 Finalized the DNS standard with RFC 1034 and 1035 — still in use after 40 years
  • 2003 Received the ACM SIGCOMM Award and the 2005 IEEE Internet Award
DNS — turning hard-to-memorize IP addresses into human-readable namesDNS · Inventor of Domains
04
Tim Berners-LeeTim Berners-Lee
Inventor of World Wide WebCERN → MIT → W3C1955~Present

WWW · HTTP · HTML · URL — the four web standards he designed alone in a single year

  • 1989 Submitted 'Information Management: A Proposal' at CERN — the beginning of the WWW
  • 1990 Simultaneously implemented the first web browser, web server, HTML, HTTP, and URL
  • 1994 Founded the W3C (World Wide Web Consortium) — web standards governance
  • 2016 Received the Turing Award and was knighted by the Queen of England
WWW · HTTP · HTML · URL — the four pillars of the web humanity uses every dayWWW · Founder of the Web
05
Jon PostelJon Postel
Editor of RFCs · Founder of IANAUCLA → USC ISI1943~1998

The man who managed every internet standards document for 30 years — 'The Internet's Postmaster'

  • 1969 As a UCLA PhD student, participated in operating the first ARPANET host
  • 1972 Began as RFC Editor — managed Internet standards documents for 30 years
  • 1981 Authored key standards including RFC 791 (IP), RFC 793 (TCP), and RFC 1591 (DNS)
  • 1988 Founded IANA (Internet Assigned Numbers Authority)
  • 1998 Passed away from cardiac surgery complications at age 55; inducted into the Internet Hall of Fame
RFC · IANA · DNS · port numbers — the operational foundation of all internet standardsRFC EDITOR · Internet Postman
🌐
In a nutshell
Cerf & Kahn (TCP/IP) → Mockapetris (DNS) → Berners-Lee (WWW) → Postel (RFC · IANA). Between 1969 and 1998, five people laid every pillar of the modern internet.

🤔 Why Do You Need to Know Networking?

Developing without it vs. developing with it
❌ Without knowing it
🔍
Can't find the root cause of an outage
When you get a report that 'the site is slow' you can only guess whether it's DNS, the server, or the network
🚪
Hard to pass interviews
You can't answer basic questions about TCP, HTTP, and HTTPS and often fail early in technical interviews
🔐
Risk of security incidents
Carelessly applying HTTPS, CORS, and authentication leads to data leaks, CSRF, and session hijacking
📚
Always depending on search engines
Every time you design an API or add authentication you search from scratch and can't verify the results
✅ With knowing it
🩺
Diagnose the root cause in 5 minutes
Looking at DevTools — 'DNS 200ms?', 'TLS handshake taking long?' you immediately pinpoint which stage is the bottleneck
🎯
Confidence in interviews
Even with deep follow-up questions you get to the core and can answer 'why does it work this way'
🛡️
Secure services
You naturally apply standard security patterns (HTTPS · CORS · JWT expiry) and prevent incidents before they happen
🏗️
Able to design from scratch
You can design REST APIs, authentication flows, and real-time communication from the ground up and confidently add new features
💡
Once you properly grasp networking, it becomes a solid foundation across debugging, interviews, and real-world work alike. Knowing 'why things work the way they do' for each concept helps you absorb new technologies much faster as they appear.

👨‍💻 The People Who Built Networking — The Identity of 6 Protocols

Each protocol's inventor introduces themselves
Vint Cerf & Bob Kahn
👤
"Hi! We're Vint Cerf and Bob Kahn. We created IP back in 1974!"
1974
📍
IP
IP — the addressing agreement for computers

I'm the 'address' assigned to every computer. Numbers like 192.168.1.1 determine where to send data.

Vint Cerf & Bob Kahn 가 만들었어요

Back then, there was no way for different networks to communicate with each other. We designed IP around the idea of 'connecting multiple networks into one.'

Vint Cerf & Bob Kahn
👤
"We didn't just create IP! We made TCP too."
1974
🤝
TCP
TCP — the reliable delivery agreement

I make sure data arrives completely and in order. If anything is lost, I send it again!

Vint Cerf & Bob Kahn 가 만들었어요

IP alone couldn't detect lost data, so we co-designed TCP as a sibling protocol to add reliability.

Paul Mockapetris
👤
"Hi! I'm Paul Mockapetris. I designed DNS back in 1983."
1983
🌐
DNS
DNS — the Internet's phone book

I translate names like codemaster40.com into numbers like 203.0.113.25.

Paul Mockapetris 가 만들었어요

As the Internet grew, a single hosts.txt file wasn't enough. So I built DNS with a distributed, hierarchical structure — the idea of 'don't pile everything in one place; spread it out.'

자세히 알아보기 →
Tim Berners-Lee
👤
"Hi! I'm Tim Berners-Lee. I created HTTP at CERN."
1991
📨
HTTP
HTTP — the web page agreement

I'm the protocol used when asking 'please send me this page.' We communicate with GET and POST.

Tim Berners-Lee 가 만들었어요

I invented HTTP alongside the WWW (World Wide Web) vision of 'linking documents worldwide with hyperlinks.' It started as a small internal project!

Netscape team
👤
"Hi! We're the Netscape team. We created the foundation of HTTPS."
1994
🔒
HTTPS
HTTPS — HTTP with a lock

I'm HTTP's secured sibling. TLS encryption ensures nobody can eavesdrop.

Netscape team 가 만들었어요

Back when HTTP was plaintext, passwords and card numbers were exposed. We came up with the idea of 'putting communication in a sealed envelope' and created SSL (later TLS).

Ian Hickson
👤
"Hi! I'm Ian Hickson. I designed WebSocket while working on web standards."
2008
⚡
WebSocket
WebSocket — the real-time bidirectional channel

I handle real-time communication like chat and notifications. Once connected, both sides can freely exchange messages.

Ian Hickson 가 만들었어요

HTTP's request-then-disconnect cycle was frustrating. We needed a channel that 'stays open once connected,' so WebSocket was standardized.

Why You Need to Know Networking

In a nutshell: Every service = network calls. The root cause of slow pages and dropped connections lies in the network.

Tool Mapping — The English abbreviations in each cell are just acronym/convention names; focus on the descriptions next to them

Use caseKey protocol
Addressing & routingIP · DNS · CIDR · NAT (computer addresses + name-to-address resolution + routing)
Data transferTCP · UDP · QUIC (protocols for sending data reliably / quickly)
Application communicationHTTP/1.1 · 2 · 3 · WebSocket · gRPC (rules for web, real-time, and high-speed API communication)
SecurityTLS · HTTPS · OAuth · JWT (encryption + login token standards)
Real-timeWebSocket · SSE · Long Polling (always-on connection between server ↔ browser)
InfrastructureCDN · Load Balancer · Proxy (global cache + traffic distribution + relay server)

5 Key Reasons

ReasonMeaning
TCP/IPThe foundation of all internet. Starts with the 3-way handshake (exchanging three signals to begin a connection)
HTTP methods & status codesThe grammar of API design. Know exactly what 404 · 500 · 200 mean
HTTPS · TLS (Transport Layer Security — the standard for encrypting communications)The actual mechanics behind the padlock icon
CORS (Cross-Origin Resource Sharing — the rule that allows communication between different domains) · SOPThe #1 headache in frontend debugging
CDN (Content Delivery Network — a network of servers that places content copies around the world) · cachingDetermines 80% of the user-perceived performance

Key takeaway: Networking is invisible infrastructure. Without it, debugging takes 5× longer. With it, you identify the root cause immediately.

🤖 Try Asking AI Like This

Knowing the concepts in this lesson lets you give AI specific instructions. Not a vague 'fix this' but a request with vocabulary — that is the starting point for saving tokens (the unit of text AI processes at once).

  • ▸'Explain the flow of the HTTP (web communication protocol) request in this code, step by step'
  • ▸'Between REST (REpresentational State Transfer — an API design style that represents resources with URLs) and gRPC (Google's high-speed API communication method), which fits this situation better'
  • ▸'Give me the 3 points interviewers ask about when a CORS (rule for allowing cross-domain communication) error occurs'

Why This Saves Tokens

When you don't know the concepts, even after receiving an AI response you have to ask 'What does that mean?' all over again. That follow-up question consumes tokens. Learn the concepts once and the conversation ends in a single exchange.

Read this first: Vibe Basics — Reading Errors·Debug·Packages
Up next: Network Basics — IP·DNS·Port·OSI
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