The internet in pictures

New to networks? Each idea below has a picture first, a few lines after it, and the zev command that goes with it. Nothing here needs you to know how the internet works. ## How a page reaches you When you open a page, four things happen in order. If any one of them fails, the page doesn't load, and the browser usually just says "no internet". ```diagram type: flow title: Opening www.example.com --- Your Wi-Fi or cable | the computer joins a network and gets an address | | 📶 ~ The router | the box at home or the office passes everything on | | 📡 ~ DNS | "where is www.example.com?" answered with an address, like a phone book | accent | 🔤 ~ The site | your computer connects to that address and asks for the page | good | 🌍 ``` `zev doctor` checks these one after another, says which one is broken, and fixes what it can: ```bash zev doctor # which step fails, and why zev doctor --fix # fix it, check again ``` More: [When the internet doesn't work](/docs/en/doctor). ## DNS: the phone book Computers reach each other by numbers (addresses like 104.16.123.96); people use names. DNS turns one into the other. Your computer asks a DNS server, and trusts whatever it answers. On some networks the answer is a lie: an address that isn't the site. ```diagram type: sequence title: An honest answer and a forged one lanes: Your computer | A DNS server | The site alt: The computer asks a DNS server where a name is; an honest server answers with the site's address and the site proves it with its certificate; a forged answer points somewhere else, and that address can't show the site's certificate --- Your computer -> A DNS server : where is www.example.com? A DNS server --> Your computer : 104.16.123.96 Your computer -> The site : hello, www.example.com? The site --> Your computer : here is my certificate for www.example.com | good note Your computer : a forged answer would point elsewhere, and that address can't show this certificate | warn ``` ```bash zev dns check # what this network does to DNS zev dns verify www.example.com # which DNS servers told the truth, proven by the site's certificate sudo zev dns on # use the ones that answer honestly from here ``` More: [DNS that works on any network](/docs/en/dns). ## Proxy and VPN: one road, or all of them A **proxy** is a computer elsewhere that fetches pages for you, so a filter between you and the site sees only the proxy. A program uses it when it's told to. A **VPN** sends *every* program's traffic to it, without asking each one. ```diagram type: cards title: Three ways for your traffic --- ➡️ | Directly | each program connects to the site itself: fastest when nothing is in the way | 🔀 | Through a proxy | programs you point at it go through your server; the rest go directly | accent 🔒 | Through a VPN | every program goes through it, and a kill switch can make sure nothing leaks if it stops | good ``` ```bash zev proxy add home 'vless://…' # your server's link zev proxy share on # a proxy port for any program: 127.0.0.1:10808 sudo zev vpn on --kill-switch # every program, and nothing gets out if it stops sudo zev vpn direct -- steam # one program outside the VPN ``` More: [Your own proxy](/docs/en/proxy), [VPN for the whole computer](/docs/en/vpn). ## Many servers: the fastest, and a spare A server that's fast in the morning can be blocked by the evening. With several, zev measures them all and uses the best, and switches by itself when one stops. ```diagram type: flow title: A pool of servers --- Measure | every server timed at once, every 30 minutes | | ⏱️ ~ Use the best | the three best kept running; each connection takes the fastest that answers | good | 🏆 ~ one stops answering Switch | the next connection takes the next one; nothing for you to do | accent | 🔁 ``` ```bash zev proxy use auto # every saved server, as a pool zev proxy bench # each server: where it exits, latency, speed, which sites it reaches zev proxy history # which one is really reliable, over days ``` ## Latency, jitter and a full line **Latency** is how long a message takes to go and come back. **Jitter** is how much that swings. When a line is full (someone uploads a video), the modem queues everything else behind it, and latency can jump from 20 ms to half a second. That's **bufferbloat**: the line is fast, but calls freeze and games lag. ```diagram type: stats title: The same line, quiet and full --- 20 ms | quiet | a message goes and comes back | 4 | good 480 ms | while uploading | it waits in the modem's queue behind the upload | 100 | warn 22 ms | uploading, with zev tune | a smart queue on this computer keeps the line from overfilling | 5 | good ``` ```bash zev tune check # latency, jitter, loss, speed, and how much a full line adds sudo zev tune on # fix it, one change at a time, keeping only what helped zev tune history # when the line is bad, hour by hour ``` More: [A better internet line](/docs/en/tune). ## A spare connection With Wi-Fi and a phone (or a cable and Wi-Fi), one can take over when the other stops. zev checks each through its own device, so it knows the spare works before it needs it. ```diagram type: flow title: When the main connection stops --- Wi-Fi | carries everything; both checked every 5 seconds | good | 📶 ~ Wi-Fi stops reaching the internet for 15 s Phone | takes over by itself | accent | 📱 ~ Wi-Fi answers for 30 s Wi-Fi | back on the main one | good | 📶 ``` ```bash zev tune links # every connection, and which one carries traffic ``` ## Which command do I need? ```diagram type: cards title: Start from what you see --- 🚫 | "No internet" | zev doctor: finds which step is broken, and fixes it | accent 🐢 | Slow, calls freeze, games lag | zev tune check, then sudo zev tune on | 🔤 | A site doesn't open, others do | zev dns verify <site>, then zev proxy why <site> | 🔀 | A site is blocked here | zev proxy add, then zev proxy share on (or sudo zev vpn on) | 🧭 | Which server should I use? | zev proxy bench | 🏠 | VPN at the café, not at home | sudo zev vpn trust (at home) | 📱 | Honest DNS for the phone and TV | sudo zev dns share on | ```