[Bloat] [Ecn-sane] 2019-12-31 docsis strict priority dual queue patent granted

Dave Taht dave at taht.net
Sat Jan 25 11:04:29 EST 2020

Toke Høiland-Jørgensen <toke at toke.dk> writes:

> Dave Taht <dave.taht at gmail.com> writes:
>> To be deliberately contrarian - (I do try to only pay attention to
>> this a few days a month) - after also re-reading
>> https://www.cablelabs.com/technologies/low-latency-docsis and the
>> associated white papers (yes, 24 hours on a plane can do this to
>> you)
>> 1) I've never been able to figure out where the 99 percentile
>> latency
>> figure so often cited came from. on the upstream which typically
>> runs
>> well below 20Mbit, a single IW10 burst at 10Mbit is 1.3ms, so I've
>> generally figured it was either a long term figure, or calculated
>> from
>> a much higher (100mbit? 1gbit?) downstream rate against some load
>> that's never been documented. (that I know of, please note that I
>> don't
>> read much of the traffic about this stuff)
>> 2) There is a lot of valuable looking stuff in the lower level
>> aspects
>> of the docsis LL standard. I'd noted it when I first read it, but
>> achieving .9ms baseline a/g latency finally does make it competitive
>> with fiber with whatever the heck "pgm" is. So far as I knew, the
>> overlapping grant request and estimator functions documented in the
>> patent are already present in most cablemodems already, and not
>> really
>> tied to the ll spec... but that data would be interesting to get out
>> of the modem itself, somehow. The histogram is made available via a
>> MIB to the operator. It would be nice if those MIBs were also
>> visible
>> to the user somehow.
>> 3)
>> In the docsis-ll white paper and spec it lays out cmts requirements
>> also. With the cmtses currently exhibiting 500+ms of latency at
>> 100Mbit loaded, from a mere "solving bufferbloat" perspective -
>> getting just pie there to work would be *marvelous* - it would be
>> superior to any of the fiber deployments I know of. dualpi, even if
>> not configured for l4s ecn support, would be a godsend. The ECO for
>> cablemodems at least, went out over a year ago.
>> some aqm tech becoming common on these head ends would also spur
>> deployment of aqm (or fq + aqm) tech on fiber also. But I've seen no
>> info as to what's going into cmtses today. Haven't seen any
>> announcements...
>> I still have no idea what is going to happen on 5G.
> I have heard about 5G vendors implementing CoDel on their
> modems.

That's the best news I've heard all year.

> Maybe
> what will end up happening is that all the promises of "low-latency
> networking" on 5G will end up being true simply because the vendors
> finally fix their bloat? ;)

One can hope. I must admit that I still think fiber to the home is a
way better idea than fiber to the pole, and I'd really like delegated
/60 at the very least, regularly available, over (X)G. I tether a lot
these days and don't have ipv6 on my tether at all...

> -Toke
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