[Cerowrt-devel] Comcast Uplink Buffers

Dave Taht dave.taht at gmail.com
Thu Mar 5 10:43:32 EST 2015

well, cerowrt's inbound shaper runs out of cpu at +60mbits. That is
possibly part of your problem.

the peaks you are seeing are not bad - but to me, probably indicative
of running out of cpu, which will among other things, drop packets

As comcast has rolled out 100mbit+ service in a ton of places
(including my home), we really, really, really need to find a way to
do better rate shaping at higher speeds (or develop a faster policer)
on some successor hardware.

If you turn off inbound shaping (0 for that parameter) my measurements
typically show over 600ms of latency on inbound on comcast at 100mbit
down, but at least, doing the tcp_upload tests, we can hold the upload
more under control. It is a totally unsatisfactory thing to have
downloads got so much out of control, it really messes up other
things, inside of a few seconds, on big downloads, but at this point I
have to recommend turning off inbound shaping and just living with it.

Very high on my list now is finally writing (or tom sawyering someone
into writing!) "bobbie - the kinder, gentler policer" in the hope that
that could actually run faster and better than shaping does on this
low end hardware.

On Thu, Mar 5, 2015 at 7:35 AM, William Katsak <wkatsak at gmail.com> wrote:
> Hello all,
> I just moved and had to switch my ISP from Optimum (Cablevision) to Comcast
> (100/10 link).
> I am running my own port of simple.qos over to Debian/Ubuntu, and it worked
> fine on Cablevision (I basically use scripts in if-pre-up.d and
> if-post-down.d to set the variables set up/tear down simple.qos).
> However, since I moved over to Comcast, I am seeing something like 600 ms of
> uplink buffering according to Netlyzer. Also, the Internet browsing "feels"
> slow when Netflix is in use elsewhere in the apartment (like before I knew
> anything about bufferbloat).
> My config looks like this:
> UPLINK=7500
> DOWNLINK=85000
> QDISC=fq_codel
> LLAM="tc_stab"
> LINKLAYER="none"
> STAB_MTU=2047
> LIMIT=1001   # sane global default for *LIMIT for fq_codel on a small memory
> device
> ITARGET="auto"
> ETARGET="auto"
> TC=`which tc`
> #TC="sqm_logger tc"# this redirects all tc calls into the log
> IP=$( which ip )
> INSMOD=`which modprobe`
> TARGET="5ms"
> IPT_MASK="0xff"
> IPT_MASK_STRING="/${IPT_MASK}"     # for set-mark
> I've also attached the output of a run of rrul against
> netperf.bufferbloat.net.
> Any insight?
> Thanks,
> Bill
> --
> ****************************************
> William Katsak <wkatsak at gmail.com>
> ****************************************
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> Cerowrt-devel at lists.bufferbloat.net
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Dave Täht
Let's make wifi fast, less jittery and reliable again!


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