Networking
Wi-Fi
Ethernet's page describes the Link layer's job as "local, one-hop delivery by MAC address." Wi-Fi does exactly that same job — the same frames, the same MAC addressing, the same place in the stack — over radio waves instead of a copper cable. Everything built on top, from IP upward, has no idea which one it's actually running over.
- What it is
- A family of wireless standards (802.11) doing Ethernet's job over radio instead of a cable.
- Mental model
- The same postal delivery job as Ethernet, with the physical wire replaced by a radio broadcast anyone in range can technically hear.
- Key numbers
- Marketed as "Wi-Fi 4/5/6/6E/7" (802.11n/ac/ax/ax/be); operates in the 2.4GHz, 5GHz, and newer 6GHz bands.
- Reach for it when
- Never chosen directly — a device either has a Wi-Fi radio or it doesn't; the application layers above never know the difference.
Same job, different medium
A Wi-Fi frame still has source and destination MAC addresses, still gets switched and routed by exactly the same logic covered on the Ethernet and Router pages, and still just carries an IP packet as its payload. The only real difference is the physical medium — a broadcast radio signal instead of electrical pulses down a wire — which is also exactly why that difference matters enormously for one specific thing: security, covered below.
SSIDs and association
An Ethernet cable's physical connection is the "join this network" step — plug it in, done. A wireless device has no equivalent physical certainty, so Wi-Fi adds an explicit step: it scans for broadcast SSIDs (network names), then associates with one — a short handshake authenticating the device and the access point to each other before any real data frame is allowed to pass. Only after association succeeds does a device behave, from every layer above, exactly like it's plugged into an Ethernet switch.
2.4GHz vs. 5GHz vs. 6GHz
Every Wi-Fi band trades off the same two physical properties against each other:
| Band | Range & penetration | Speed & interference |
|---|---|---|
| 2.4GHz | Longest range, best at penetrating walls/floors | Slowest, most crowded — shared with Bluetooth, microwaves, and every neighboring router |
| 5GHz | Shorter range, attenuates more through walls | Faster, meaningfully less crowded than 2.4GHz |
| 6GHz | Shortest range of the three | Fastest, cleanest spectrum — newest devices only |
Lower frequency radio waves travel further and bend around/through obstacles more easily — the same physics that makes AM radio reach further than FM. There's no band that simply wins; the right choice depends on whether range or throughput matters more for a given device's location.
WEP through WPA3
Because a Wi-Fi signal is, by its nature, receivable by anyone within range, encryption at this layer carries weight an Ethernet cable never needed as urgently — nobody can silently tap a signal that never left a physical wire. WEP (the original standard) is now completely broken and should never be used. WPA, then WPA2, then WPA3 each replaced the previous generation's cryptographic weaknesses — WPA2 is still widely deployed and considered reasonably secure with a strong password; WPA3 is the current standard, adding protection even for public/open networks that previously had no encryption at all.
Real-world applications
- Nearly every consumer device without a physical port — phones, laptops, tablets rely on Wi-Fi as their only Link-layer option.
- Industrial wireless sensor networks — deploying sensors across a large facility without running physical cable to each one.
- Wi-Fi as an embedded peripheral — chips like the ESP32 class of microcontrollers integrate a full Wi-Fi radio directly on-die, letting a small embedded project join a wireless network with minimal extra hardware.
Gotchas
- 2.4GHz congestion in dense apartment buildings — dozens of overlapping networks all sharing the same few channels — is a classic, physics-driven cause of "my Wi-Fi is slow here" that switching routers won't fix.
- A device "connected to Wi-Fi" with no internet access has successfully associated with the access point — the Wi-Fi link itself is fine — but is failing somewhere further up the stack, commonly DHCP or DNS; treat "Wi-Fi is connected" and "the internet works" as two separate, independently-failing things.
- Switching to 5GHz isn't automatically an upgrade — its shorter range and weaker wall penetration can leave a device with a worse connection than 2.4GHz once it's a room or two away from the access point, despite the higher theoretical speed.