Networking· 10 min read

How Does the Internet Actually Work? (Not the Oversimplified Version)

You've seen the diagrams. A laptop, a cloud, some arrows. That's not wrong — it's just useless. Here's what's really happening when you stream, browse, and send data across the internet.

SBy Subnet Savy

At a Glance

  • →The internet is a network of networks — your home router connects to your ISP, which connects to backbone providers, which connect to data centers. No single company owns all of it.
  • →Data doesn't travel as files — it travels as packets, small chunks that take independent routes and reassemble at the destination. A single web page might arrive via 40+ packets.
  • →TCP/IP became the internet's universal language on January 1, 1983 — called “flag day,” when ARPANET switched to the protocol developed by Vint Cerf and Bob Kahn.
  • →There are over 4,165 data centers in the US alone — roughly 38% of all data centers worldwide.
  • →Internet traffic grew 440% between 2015 and 2021 — from 0.6 to 3.5 zettabytes annually — with no slowdown in sight.
  • →Your ISP sees the metadata of everything you do online unless you use a VPN or encrypted protocols.

The Internet Is Not a Cloud

Every metaphor about “the cloud” implies something weightless and intangible. The reality is steel, fiber optic glass, and seawater.

The internet is physical. It runs through over 1.3 million kilometers of undersea cable connecting continents, through conduits buried under city streets, through cell towers on building rooftops. When you stream something from a server in Virginia, actual light pulses travel through glass fiber to your router.

What makes it feel like magic is that this infrastructure belongs to hundreds of thousands of different companies — ISPs, backbone providers, hosting companies, CDNs — all connected through agreements called peering arrangements. Your internet traffic hops between these networks seamlessly, guided by a protocol called BGP (Border Gateway Protocol). You never see the seams.

When Coordination Breaks Down

The 2021 Fastly outage knocked Reddit, GitHub, and The New York Times offline for nearly an hour — not because those servers failed, but because the routing layer couldn't direct users to them. The internet doesn't fail gracefully. It just stops. (Fastly incident report, 2021)

Packets: Why Data Travels in Pieces

Here's the counterintuitive thing about how your data moves: it doesn't travel as a single stream. It gets cut into small pieces called packets — typically 1,500 bytes each — sent independently, and reassembled on the other end.

Think of it like mailing a book. Instead of shipping the whole thing in one box, you tear it into 300-page chunks, mail each chunk through a different postal route, and trust that they'll all arrive and be reassembled in order. That sounds chaotic. It's actually brilliant.

  • •If one route gets congested, packets reroute around it automatically
  • •Multiple conversations can share the same wire simultaneously
  • •A dropped packet only requires retransmitting that packet, not the whole file

The original ARPANET researchers needed a network that could survive a nuclear strike — one with no single point of failure. Packet switching was the answer. Every router makes independent forwarding decisions based on current conditions.

TCP/IP: The Universal Language

Packets need rules. Two computers can't exchange data if they don't agree on how to label packets, what to do with dropped ones, or how fast to send them. That's what TCP/IP provides.

ProtocolLayer
IPNetwork
TCPTransport
UDPTransport
HTTP/HTTPSApplication

Why TCP and UDP coexist: TCP guarantees delivery but adds overhead. For a file download, a missing packet is unacceptable. For a live video call, a dropped frame is better than a half-second freeze waiting for retransmission. UDP trades reliability for speed. Most streaming services use UDP at the transport layer.

What Happens When You Hit Play on Netflix

This is where the abstract becomes concrete. Here's the actual sequence:

01

DNS lookup

Your device asks a DNS resolver to translate netflix.com into an IP address (see our DNS explainer for the full breakdown).

02

TCP handshake

Your device and Netflix’s server exchange three packets to establish a connection (SYN → SYN-ACK → ACK).

03

TLS negotiation

Since it’s HTTPS, they negotiate encryption keys before any video data moves.

04

CDN routing

Netflix doesn’t serve you from one server in California. Its CDN routes you to the nearest edge server, possibly in your city.

05

Adaptive bitrate

The player requests video in small chunks and monitors how fast they arrive. If your connection slows, it drops from 4K to 1080p automatically.

06

Buffering

A buffer of 5–30 seconds of video is pre-downloaded so playback stays smooth even if your connection hiccups.

Step 1 goes deeper than you think. Read our full DNS explainer — covering the 4 servers behind every lookup, DNS privacy risks, and the outages that brought down the internet.

Why it buffers: When the buffer runs out faster than new chunks arrive — usually because your connection is congested, your router is overloaded, or the CDN edge server is under load — you get the spinning wheel. A VPN adds latency at steps 3 and 4, which is why streaming over a VPN often degrades quality.

What Your ISP Actually Sees

Most people assume their ISP is just a pipe — neutral infrastructure that moves data without looking at it. That's not accurate.

Your ISP can see:

  • •Every domain you visit (via DNS queries, unless you use encrypted DNS)
  • •Every IP address you connect to
  • •Timing and volume of your traffic

HTTPS encrypts the content of your web browsing — your ISP can't read your messages or passwords. But the metadata — which sites, when, how often — remains visible. In several countries, ISPs are legally required to retain this data for 6–24 months.

A VPN encrypts all traffic between you and the VPN server, so your ISP sees only that you're connected to a VPN — not what you're doing. The tradeoff: you now trust the VPN provider's logging policy instead of your ISP's. DNS-over-HTTPS (DoH) is a lighter option that only encrypts DNS queries.

Frequently Asked Questions

What’s the difference between the internet and the web?

The internet is the physical and protocol infrastructure — cables, routers, IP addresses. The World Wide Web is one application that runs on top of it, using HTTP to serve pages. Email, video calls, and gaming are also internet services, but they’re not “the web.”

Why is internet speed measured in bits, not bytes?

Historical convention from telecommunications, where speed was measured in bits per second. A “100 Mbps” connection transfers 100 megabits per second — divide by 8 to get megabytes (about 12.5 MB/s). This is why your 100 Mbps plan downloads a 1 GB file in about 80 seconds, not 10.

What happens when you type a URL and press Enter?

In order: DNS lookup → TCP connection → TLS handshake → HTTP request → server processes request → HTTP response → browser renders HTML → browser fetches CSS, JS, images → page fully loaded. Typically 300–500ms for a fast site.

Why does restarting your router fix things?

Routers maintain state tables tracking active connections. When these tables get stale, corrupted, or full, new connections fail. A restart flushes everything, gets a fresh IP from your ISP via DHCP, and re-establishes routing. It’s not magic — it’s clearing accumulated garbage.

The Bottom Line

The internet is a coordination miracle: thousands of companies, millions of devices, and billions of people sharing infrastructure that nobody fully controls, governed by protocols that nobody owns, running reliably enough that we get annoyed when it slows down for 30 seconds.

Packet switching, TCP/IP, BGP, CDNs — these aren't buzzwords. They're the design decisions made by a small group of researchers in the 1970s and 80s that now move 3.5 zettabytes of data every year. Understanding how it works helps you troubleshoot your own connection, make smarter choices about VPNs and privacy, and recognize when “slow internet” is your router versus your ISP versus a congested CDN.

Want to go deeper on how DNS fits into this picture? Read our DNS explainer next.

Want to see TCP/IP, BGP, VPNs, and the full network stack explained in video form?

Watch on YouTube — Subnet Savy

Sources

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