[Bloat] Question about fq_codel vs modem buffers

[Rich Brown <richb.hanover@gmail.com>]

I posted a message about using SQM & OpenWrt on Tom's Hardware, and got a response from someone who's somewhat knowledgeable. I'm not sure of the proper response, so I wanted to ask here first. Here's the question that has me stumped.

http://www.tomshardware.com/answers/id-2615979/high-latency-person-internet.html#15786081

My thoughts:

I know fq_codel takes control of the bottleneck by being set to a couple percent below the fastest link speeds observed in each direction.

The author of the rebuttal says that the (DSL or Cable) modem buffers will fill up if the "upload drops from 3 to 2mbps". I can think of two ways this can happen:
	- Actual link bit rate drops
	- Congestion/oversubscription in the head end causes effective data rate to drop

But I don't know enough about the physical characteristics of cable/dsl links to understand how they actually work, nor how fq_codel can (or can't) accommodate degradation.

Could someone help me shape a response? Thanks.

Rich