Bufferbloat

What is bufferbloat?

Your call can lag even when downloads are fast. Bufferbloat means excess delay from data waiting in a network queue. A queue grows when data arrives faster than the next link can send it. Data keeps leaving while more arrives; it does not wait for the queue to fill.

IETF guidance on queue management explains why long queues can hurt calls and other tasks that need a quick reply.

Check when the delay happens

• Try the same call when no large upload or download is running. Note whether the problem improves.
• With the owner's agreement, pause a large transfer in the app that started it. Resume it after the comparison so a backup is not left paused.
• If you use a test that measures delay with and without load, run it when nobody needs the connection. The test itself can disrupt calls.
• Save the test result, time, device, and whether you used WiFi or Ethernet. A repeatable increase under load supports investigating congestion. One result does not locate the queue or prove your router is at fault.

What can help?

Queue management can reduce this delay. Router features called SQM or AQM may help; a generic QoS switch may only change which traffic gets priority. Before changing one, find the maker's instructions for your exact model, record the old values, and plan how to restore them. Ask support if the guide does not explain the required speed settings.

A faster plan or new router is not a guaranteed cure. Fiber can also have queues. If the problem persists, send your provider the quiet-versus-busy results before spending money.