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

Toke Høiland-Jørgensen toke at toke.dk
Fri Jan 24 04:51:19 EST 2020

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. 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? ;)


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