[LibreQoS] [Starlink] [Rpm] [EXTERNAL] Re: Researchers Seeking Probe Volunteers in USA

dan dandenson at gmail.com
Mon Mar 13 12:12:54 EDT 2023

" [SM] For a home link that means you need to measure on the router,
as end-hosts will only ever see the fraction of traffic they
sink/source themselves..."
 [SM] OK, I will bite, how do you measure achievable throughput
without actually generating it? Packet-pair techniques are notoriously
imprecise and have funny failure modes.

High water mark on their router.   Highwater mark on our CPE, on our
shaper, etc.  Modern services are very happy to burst traffic.  Nearly
every customer we have will hit the top of their service place each
day, even if only briefly and even if their average usage is quite
low.  Customers on 600Mbps mmwave services have a usage charge that is
flat lines and ~600Mbps blips.

"  [SM] No ISP I know of publishes which periods are low, mid, high
congestion so end-users will need to make some assumptions here (e.g.
by looking at per day load graphs of big traffic exchanges like DE-CIX
here https://www.de-cix.net/en/locations/frankfurt/statistics )"

You read this wrong.  Consumer routers run their daily speeds tests in
the middle of the night.  Eero at 3am for example.  Netgear 230-430am.
THAT is a bad measurement of the experience the consumer will have.
It's essentially useless data for the consumer unless they are
scheduling their downloads at 3am.  Only a speed test during use hours
is useful and that's also basically destructive unless a shaper makes
sure it isn't.

re per segment latency tests " [SM] Well is it really useless? If I
know the to be expected latency-under-load increase I can eye-ball
e.h. how far away a server I can still interact with in a "snappy"

Yes it's completely useless to the customer.  only their service
latency matters.  My (ISP) latency from hop 2 to 3 on the network has
zero value to them.  only the aggregate.  per segment latency testing
is ONLY valuable to the service providers for us to troubleshoot,
repair, and upgrade.  Even if a consumer does a traceroute and get's
that 'one way' testing, it's irrelevant as they can't do anything
about latency at hop 8 etc, and often they actually don't know which
hops are which because they'll hidden in a tunnel/MPLS/etc.

On Mon, Mar 13, 2023 at 9:50 AM Sebastian Moeller <moeller0 at gmx.de> wrote:
> Hi Jeremy,
> > On Mar 13, 2023, at 16:08, Jeremy Austin <jeremy at aterlo.com> wrote:
> >
> >
> >
> > On Mon, Mar 13, 2023 at 3:02 AM Sebastian Moeller via Starlink <starlink at lists.bufferbloat.net> wrote:
> > Hi Dan,
> >
> >
> > > On Jan 9, 2023, at 20:56, dan via Rpm <rpm at lists.bufferbloat.net> wrote:
> > >
> > >  You don't need to generate the traffic on a link to measure how
> > > much traffic a link can handle.
> >
> >         [SM] OK, I will bite, how do you measure achievable throughput without actually generating it? Packet-pair techniques are notoriously imprecise and have funny failure modes.
> >
> > I am also looking forward to the full answer to this question. While one can infer when a link is saturated by mapping network topology onto latency sampling, it can have on the order of 30% error, given that there are multiple causes of increased latency beyond proximal congestion.
>         So in the "autorates" a family of automatic tracking/setting methods for a cake shaper that (in friendly competition to each other) we use active measurements of RTT/OWD increases and there we try to vary our set of reflectors and then take a vote over a set of reflectors to decide "is it cake^W congestion", that helps to weed out a few alternative reasons for congestion detection (like distal congestion to individual reflectors). But that dies not answer the tricky question how to estimate capacity without actually creating a sufficient load (and doubly so on variable rate links).
> > A question I commonly ask network engineers or academics is "How can I accurately distinguish a constraint in suppl from a reduction in demand?"
>         Good question. The autorates can not, but then they do not need to as they basically work by upping the shaper limit in correlation with the offered load until it detects sufficiently increased delay and reduces the shaper rates. A reduction n demand will lead to a reduction in load and bufferbloat... so the shaper is adapted based on the demand, aka "give the user as much thoughput as can be done within the users configured delay threshold, but not more"...
> If we had a reliable method to "measure how much traffic a link can handle." without having to track load and delay that would save us a ton of work ;)
> Regards
>         Sebastian
> >
> > --
> > --
> > Jeremy Austin
> > Sr. Product Manager
> > Preseem | Aterlo Networks
> > preseem.com
> >
> > Book a Call: https://app.hubspot.com/meetings/jeremy548
> > Phone: 1-833-733-7336 x718
> > Email: jeremy at preseem.com
> >
> > Stay Connected with Newsletters & More: https://preseem.com/stay-connected/

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