On 22/04/2023 4:11 am, Michael Richardson wrote:
Ulrich Speidel via Starlink <[email protected]> wrote:
> All traces (to NZ, Chile, the US, Germany and Japan) exited the SpaceX
> address space in New Zealand to a variety of upstream providers. IP
> addresses on the Starlink side of the trace beyond Dishy are, in
order of
> appearance in the traces: 100.64.0.1
<http://100.64.0.1>,
172.16.249.6, followed by 149.19.109.30
<http://149.19.109.30>
> if exiting to Hurricane Electric as upstream or 149.19.109.34
<http://149.19.109.34>
if exiting to
> Kinect. All those addresses have RTT indicating that they are in NZ.
What are you being NAT44'ed to?
Good question - can't answer this right now as Dishy is back in its
suitcase in our lab ;-)
Presumably, that IP is in NZ, and you could traceroute/ping back to it
from
elsewhere to be able to subject whatever congestion is beyond the
peering point.
Beyond peering point is an interesting thing, too. We spent a day this
week on a mountain 5 hours drive south of Auckland running Dishy out of
the back of my car, just to find that the one traceroute we took from
there shows a routing issue on the Internet side of the POP - HE sent
traffic from NZ to Australia, from where it was returned to us, adding
over 4000 km of cable to the path each way. Sigh. Ookla tests (to a
different machine in a different network in NZ) gave around half the
download rates we were observing from the two other locations we visited
(and we took 60-180 samples in each location), where that routing issue
didn't show up.
> Lowest RTT seen to the first NZ hop was 65 ms, with values between
100 and
> 200 ms being the most common.
> RTTs to the US were mostly in the high 200 ms.
> 2) The fact that we don't see more than the "usual" number of
Starlink IP
> addresses in the tracreroutes indicates that whatever IP routing may be
> happening on satellites that handle the traffic via ISLs happens at
a tunnel
> layer further down the stack.
Given Musk's age old tweet that it was "simpler than IPv6", and that
we know
that it's some kind of broadcom SDN chipset, this makes sense.
I wish they had used SR6, and done IPv4 as a service.
Indeed, but then who would want to rely on something he said a while ago?
> 3) The fact that the traffic emerges in New Zealand regardless of global
> destination also indicates that the Starlink network uses a tunnel based
> on Dishy location and a nearby gateway but does not attempt to route
to final
> destination at this point in time.
I'm not surprised about this.
I don't imagine they can world-wide stuff until all the non-ISL birds
have aged out.
Well, they do have a complete constellation with lasers, and a polar one
that's semi-complete, so in theory they should be able to do this...
> The 65 ms RTT also tells us a few things. For one, at 4,200 km great
circle
> distance on the ground, the dishy-to-gateway physical path would be
at least
> 5,000 km even if all lined up with a polar orbital plane involved.
That makes
> 10,000 km of RTT path, which translates into about 33 ms of propagation
> RTT. If cross-plane routing were involved here, we'd get a zig-zag
path - so
> roughly 1 1/2 times longer. Makes about 50 ms. In-plane only routing
would
> involve a gateway in Australia (similar length physical path dishy to
> gateway) along with a 2,000 km trans-Tasman cable leg. The 2000 km
cable leg
> would be equivalent to about 20 ms of additional RTT over the 10,000
km space
> RTT path, so that could in principle also work. Quite why everything
would
> emerge in Auckland though in this case would be a mystery to me.
I think you are saying that the your lowest RTT of 65ms is easily
supported
by physical distances alone?
And that it can't get better.
Basically, an observed RTT puts an upper bound on the length of the
possible physical path a packet can have taken. On that basis, I'm
simply looking at potentially feasible paths here. I'm just observing
that if you are landing traffic in Australia where you have multiple
gateways and POPs, it makes little sense to then also have a terrestrial
tunnel to NZ for the traffic that you are landing and that's destined to
other continents.
I mean, I'd like Auckland to be the navel of the world, but I somehow
doubt that Elon would take the same view ... Then again, at least one of
his Silicon Valley mates got NZ citizenship after just two weeks in the
country. The guy was going to promote this widely but then somehow that
didn't happen and if I correctly remember, it took an Official
Information Act request to find out that the guy had become a proud
Kiwi. FAIK he hasn't spent much if any time here since becoming a
citizen either. So who knows whether Elon might have a secret bolt hole
here? Lots of people do...
--
****************************************************************
Dr. Ulrich Speidel
School of Computer Science
Room 303S.594 (City Campus)
The University of Auckland
[email protected]
http://www.cs.auckland.ac.nz/~ulrich/
****************************************************************
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