Re: [Starlink] a puzzling starlink uplink trace

[Alexandre Petrescu <alexandre.petrescu@gmail.com>]

Le 30/08/2023 à 20:07, Dave Taht via Starlink a écrit :
> In the attached 5 minute plot from a few days ago (I can supply the
> flent.gz files if anyone wants them), I see a puzzling spike at T+155s
> to nearly 90ms of baseline latency, then down to 20ms.

20ms?

A latency of 20ms might come if these low altitude starlink sats (70km 
or so) pass by there?

Or maybe I dont see quite well these sat altitudes.

Alex


>   No degree of
> orbital mechanics can apply to this change, even factoring in an over
> the horizon connection, routing packets on the ground through LA to
> seattle, and back, or using a couple ISLs, can make this add up for
> me. A combination of all that, kind of does make sense.
>
> The trace otherwise shows the sawtooth pattern of a single tcp flow ,
> a loss (sometimes catastrophic) at every downward bandwidth change.
>
> An assumption I have long been making is the latency staircase effect
> (see T+170) forward is achieving the best encoding rate at the
> distance then seen, the distance growing and the encoding rate falling
> in distinct steps, with a fixed amount of buffering, until finally
> that sat starts falling out of range, and it choses another at T+240s.
>
> But jeeze, a 70ms baseline latency swing? What gives?  I imagine
> somehow correlating this with a mpls enabled traceroute might begin to
> make some sense of it, correlated by orbital positions....
>
>
>
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