[Starlink] insanely great waveform result for starlink

[Ulrich Speidel]

On 13/01/2023 6:13 pm, Ulrich Speidel wrote:
>
> From Auckland, New Zealand, using a roaming subscription, it puts me 
> in touch with a server 2000 km away. OK then:
>
>
> IP address: nix six.
>
> My thoughts shall follow later.

OK, so here we go.

I'm always a bit skeptical when it comes to speed tests - they're really 
laden with so many caveats that it's not funny. I took our new work 
Starlink kit home in December to give it a try and the other day finally 
got around to set it up. It's on a roaming subscription because our 
badly built-up campus really isn't ideal in terms of a clear view of the 
sky. Oh - and did I mention that I used the Starlink Ethernet adapter, 
not the WiFi?

Caveat 1: Location, location. I live in a place where the best Starlink 
promises is about 1/3 in terms of data rate you can actually get from 
fibre to the home at under half of Starlink's price. Read: There are few 
Starlink users around. I might be the only one in my suburb.

Caveat 2: Auckland has three Starlink gateways close by: Clevedon (which 
is at a stretch daytrip cycling distance from here), Te Hana and Puwera, 
the most distant of the three and about 130 km away from me as the crow 
flies. Read: My dishy can use any satellite that any of these three can 
see, and then depending on where I put it and how much of the southern 
sky it can see, maybe also the one in Hinds, 840 km away, although that 
is obviously stretching it a bit. Either way, that's plenty of options 
for my bits to travel without needing a lot of handovers. Why? Easy: If 
your nearest teleport is close by, then the set of satellites that the 
teleport can see and the set that you can see is almost the same, so you 
can essentially stick with the same satellite while it's in view for you 
because it'll also be in view for the teleport. Pretty much any bird 
above you will do.

And because I don't get a lot of competition from other users in my area 
vying for one of the few available satellites that can see both us and 
the teleport, this is about as good as it gets at 37S latitude. If I'd 
want it any better, I'd have to move a lot further south.

It'd be interesting to hear from Jonathan what the availability of home 
broadband is like in the Dallas area. I note that it's at a lower 
latitude (33N) than Auckland, but the difference isn't huge. I notice 
two teleports each about 160 km away, which is also not too bad. I also 
note Starlink availability in the area is restricted at the moment - 
oversubscribed? But if Jonathan gets good data rates, then that means 
that competition for bird capacity can't be too bad - for whatever reason.

Caveat 3: Backhaul. There isn't just one queue between me and whatever I 
talk to in terms of my communications. Traceroute shows about 10 hops 
between me and the University of Auckland via Starlink. That's 10 
queues, not one. Many of them will have cross traffic. So it's a bit 
hard to tell where our packets really get to wait or where they get 
dropped. The insidious bit here is that a lot of them will be between 1 
Gb/s and 10 Gb/s links, and with a bit of cross traffic, they can all 
turn into bottlenecks. This isn't like a narrowband GEO link of a few 
Mb/s where it's obvious where the dominant long latency bottleneck in 
your TCP connection's path is. Read: It's pretty hard to tell whether a 
drop in "speed" is due to a performance issue in the Starlink system or 
somewhere between Starlink's systems and the target system.

I see RTTs here between 20 ms and 250 ms, where the physical latency 
should be under 15 ms. So there's clearly a bit of buffer here along the 
chain that occasionally fills up.

Caveat 4: Handovers. Handover between birds and teleports is inevitably 
associated with a change in RTT and in most cases also available 
bandwidth. Plus your packets now arrive at a new queue on a new 
satellite while your TCP is still trying to respond to whatever it 
thought the queue on the previous bird was doing. Read: Whatever your 
cwnd is immediately after a handover, it's probably not what it should be.

I ran a somewhat hamstrung (sky view restricted) set of four Ookla 
speedtest.net tests each to five local servers. Average upload rate was 
13 Mb/s, average down 75.5 Mb/s. Upload to the server of the ISP that 
Starlink seems to be buying its local connectivity from (Vocus Group) 
varied between 3.04 and 14.38 Mb/s, download between 23.33 and 52.22 
Mb/s, with RTTs between 37 and 56 ms not correlating well to rates 
observed. In fact, they were the ISP with consistently the worst rates.

Another ISP (MyRepublic) scored between 11.81 and 21.81 Mb/s up and 
between 106.5 and 183.8 Mb/s down, again with RTTs badly correlating 
with rates. Average RTT was the same as for Vocus.

Note the variation though: More or less a factor of two between highest 
and lowest rates for each ISP. Did MyRepublic just get lucky in my 
tests? Or is there something systematic behind this? Way too few tests 
to tell.

What these tests do is establish a ballpark.

I'm currently repeating tests with dish placed on a trestle closer to 
the heavens. This seems to have translated into fewer outages / ping 
losses (around 1/4 of what I had yesterday with dishy on the ground on 
my deck). Still good enough for a lengthy video Skype call with my folks 
in Germany, although they did comment about reduced video quality. But 
maybe that was the lighting or the different background as I wasn't in 
my usual spot with my laptop when I called them.

-- 

****************************************************************
Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speidel at auckland.ac.nz
http://www.cs.auckland.ac.nz/~ulrich/
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