Hi Stephen,
> On Jun 29, 2021, at 21:48, Stephen Hemminger <step...@networkplumber.org>
> wrote:
>
> On Tue, 22 Jun 2021 22:51:18 +0000
> "Livingood, Jason" <jason_living...@comcast.com> wrote:
>
>>> It doesn't help that all the local ISP's claim 10Mbit upload even with 1G
>>> download. Is this a head end provisioning problem or related to Docsis 3.0
>>> (or later) modems?
>>
>> I'll cover this in an upcoming technical paper (mid-July I hope). Depending
>> on the DOCSIS version, CMTS, and cable modems involved you may have no AQM,
>> or buffer controls for the cable modem, or AQM (sort of) on the CMTS and in
>> the cable modem. In the Comcast network you should find AQM in the upstream
>> queue on the cable modems for which we have deployed RDK-B software (XB6 and
>> XB7), while other devices would have buffer controls.
>>
>> JL
>>
>
> Just a short update. The cable modem matters. Updated from Docsis 3.0 modem
> with bad Intel Puma chipset
> to new model with Docsis 3.1 and Broadcom and things are much more stable.
Glad that helped, rather sad state of affairs that these devices are
still in the field. (I am not fan of forced obsolescence or retiring hardware
too early, but these devices are simply barely fit for their purpose).
>
> As far as AQM, in this setup; fq_codel does much better than the Cake
> configuration. With fq_codel can
> see 700Mbit download speed. It looks like Cake is using more CPU
Yepp, it turns out that all the additional features cake brings to the
table have some computational cost. At some earlier state in development cake
was leaner and meaner than HTB+fq_codel, but that did not seem to hold.
> especialy since the Cake configuration
> is using an ifb ingress queue discipline as well.
Both cake and HTB+fq_codel require tricks for download shaping, either
a veth pair or an IFB (both seem to have a similar cost but IFB is much simpler
to set up) or for a wired only shaper, one can instantiate the
internet-download shaper as egress shaper on the interface towards the LAN.
Last I tested on an ancient single core 750 MHz MIPS, avoiding the IFB got a 5%
higher shaper limit, so not nothing, but also not a way to have your router
punch one weight class higher?
Best Regards
Sebastian
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