Router buffer-bloating...anybody knew this?

Server operators
1

Hi all,

I ran into new/old router problems.
Don’t worry my router runs fine, but I noticed some hickups from time to time.

Turns out to be buffer-bloating.

You can test yourself:

Often buffers are set far too high, same with OpenWRT, they’re TX-buffer is set at 1000 (no idea what it means, but it’s too high).
It’s not bits or bytes.

But after a lot of testing, I set the TX-buffers to 100 on all interfaces and behold, the bloating is gone.
As I noticed hickups in my network under load.

What happens is an application, could be NTP, get’s a lot of requests and the buffer is too big.
The application keeps accepting requests but the buffer can’t be emptied so it keeps full and delays traffic, that starts to stutter or worse.
Because the buffer keeps accepting but can’t deliver things go wrong.
Many routers have set the buffers too high for no reason.

Test yourself, as it will overload the buffers and show the problem.

It helped me to tune my OpenWRT better as it’s wrong on the buffers.

Let me know if it helped you.

2

This is an old, known problem. Qdiscs like fq_codel and cake tend to keep buffers small on interface level and are supposed to battle this problem. I currently run fq_codel

3

Same here, but wasn’t sure on OpenWRT by default.

Thanks for the info about fq_codel, never needed this as I never had the issue.
But it’s enabled on all my servers by default.

As for the Fritzbox, I can’t check as it has no info on it. But I don’t let it do the routing anymore.

4

pfSense has had traffic shapers since 2006 to deal with buffer bloat