Dynamic SQM Settings

Question

I've just set up my new router (WRT1900ACS) and installed OpenWRT. I have ADSL which makes it pretty hard to adjust the sqm up/download speed correctly as it differs depending on what day it is. Is there a way of adjusting those settings dynamically?

Answer 1

Do you want to apply a rate-limiting queue and change it's actual limit dynamically based on real ADSL attainable rate?

Pretty interesting goal. I don't know ready-made software doing this, but knowing you on OpenWRT, it could be possible to scirpt this up.

More than ten years ago I have done something like this with ZyXEL P-600 series modem and Linux PC-based router. It worked. But simply setting static "safe" limits on queue was much easier and more reliable. Line rates change from time to time, but they didn't changed that much, for example upstream varied from 700 to 850 kbps, so setting 650 kbps on queue was quite safe and worked very well, without dynamic adjust.

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What you need to know:

• How to query your modem about it's state
• Can your modem notify router about events (disconnect, reconnect, rate change). And how

This could be, for instance, SNMP protocol, i.e. some set of OIDs representing state values, and trap receiver on router which executes actions based on received traps. And your modem could generate traps on events.

Or, at least, find a clean scriptable way to enter modem interface and parse needed values. For P-600 there were telnet commands that produce needed values.

If you find these ways or settings, you could write scripts that either simply poll modem and call scripts updating queue parameters, or configure these scripts to be run by trap receiver.

The one caveat could be you won't fit into built-in flash and you'll need to set up extroot. But this is very easy. The other caveat is memory usage (net-snmp trapd could be memory-hungry, I don't know even if someone built it for OpenWRT).