Bufferbloat is when network equipment buffers too many packets, causing latency to balloon during heavy use. Idle ping is fine, but the moment anyone starts a download or video call, ping triples and Zoom freezes. The fix is one router setting.
Routers, modems, and even DSLAMs ship with oversized packet buffers. When the link is saturated, those buffers fill, and every new packet waits in line behind the queue. A 200-packet queue at a 50 Mbps line rate adds about 60 ms of latency. Stacked across modem, router, and ISP equipment, you can see latency jump from 15 ms idle to 300 ms loaded.
Run a speed test that measures ping during the download (not just before and after). FastSpeedTest's loaded-latency reading is designed for this. If your loaded ping is more than 2× your idle ping, you have bufferbloat.
SQM uses an algorithm called CAKE (or fq_codel) to keep queues short by dropping packets early when they would otherwise pile up. Routers that support it well:
Set the SQM download/upload caps to about 90% of your measured speed . The 10% headroom is what gives the queue room to drain. Setting them too high (above your real link rate) defeats the purpose.
With SQM tuned correctly, loaded ping should be within 5-15 ms of idle ping. Video calls stop freezing, game ping stays flat during a Steam download, and the entire household feels faster, even though the raw Mbps number is slightly lower on paper.