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From: Rich Brown <richb.hanover@gmail.com>
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Date: Fri, 1 May 2015 22:49:58 -0400
To: bloat <bloat@lists.bufferbloat.net>
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Subject: [Bloat] Question about fq_codel vs modem buffers
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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-interne=
t.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