🐢 What is Buffer Bloat? #
TL;DR: your router has a big buffer queueing ‘bulk’ traffic, which is causing delays in sending ‘interactive’ traffic.
Buffer Bloat is when network devices, like routers, store too much data in their buffers, causing high latency and jitter. It happens when large buffers hold packets longer than necessary, especially during network congestion, delaying data transmission. This can degrade performance for real-time applications like gaming or video calls, making them feel sluggish or unresponsive. Your router might queue up packets during heavy downloads, increasing ping times.
⏱️ How to detect Buffer Bloat #
We usually see buffer bloat when customers send us speed test results showing high latency while the line was being tested. It’s normal for latency to go up when the line is under load (to about 30ms), but in some cases, latency gets very high, 100ms+.
Speedtest.net will show you a small up and down arrow with latency results.
Cloudflare has a better speed test that shows you a graph with a range of latency measurements.
Note: low wifi signal can also make speed test results show high latency. Test with a cable directly connected to your router to make sure you are not seeing a wifi problem.
🎛️ How do I fix this? #
Look for a feature called ‘Smart Queues’ in your router admin interface and enable it. Not all routers have this feature. On Linux-based systems, you can also look for the fq_codel queue management algorithm and enable that on your WAN interface.
Check the documentation of your router. Often router manufacturers don’t recommend enabling smart queues for fast lines (400Mbps+).
