Packet loss
Packet loss means some data packets never reach their destination and must be re-sent—or the application skips them—which disrupts smooth audio, video, and game updates.
Why it matters
Even small loss rates hurt interactive traffic more than bulk downloads. Voice and games notice quickly; a file download may just slow slightly.
Example in UK broadband
If your line shows 0% loss to your router but loss to the wider internet, the issue may be upstream. If Wi‑Fi is busy, you can see loss on wireless hops even when the fibre line is clean.