Ping lies: the living-room TV that kept buffering
Live TV kept buffering, but the network tests looked perfect. The real numbers were hiding one level down.
The problem
The living-room TV kept buffering during live streaming. A ping test to it looked perfect: about 2 ms and zero loss.
The real numbers
The Wi-Fi controller told a different story:
| Measure | Value |
|---|---|
| Signal | about −80 dBm (very weak) |
| Link speed | about 7 Mbps |
| Retries | 12.5% |
HD streaming needs about 8 Mbps. The TV had attached to an access point on a different floor, and that link simply couldn't carry the stream. Pings are tiny, so they got through fine. Video didn't.
The fix
I wired the TV in: latency went to a flat 1 ms and the buffering stopped. It also freed up Wi-Fi airtime for every other device in the house.
Lessons
- Ping is a reachability test, not a capacity test. For Wi-Fi, look at signal, link speed and retries.
- A side effect of DNS filtering looked like a suspect at first (it was blocking some of the streaming app's analytics), but the actual video was never blocked. Check the evidence before blaming the newest change.