[Starlink] a puzzling starlink uplink trace
Dave Taht
dave.taht at gmail.com
Thu Aug 31 09:42:45 EDT 2023
On Wed, Aug 30, 2023 at 12:43 PM Sebastian Moeller <moeller0 at gmx.de> wrote:
>
> Hi Dave,
>
>
> you probably know already, but
> mtr -ezb4 www.heise.de
> will report compliant MPLS segments:
Despite any reputation for omniscience I may have acquired, I was an
ipv6 bigot in the era when MPLS was being specced, and somewhat
willfully ignored it, and did not know traceroute and mtr had gained
the ability to see it.
It would be kind of neat (for business services at least), if starlink
offered MPLS to the router. It would make some things easier. Nobody
to this day seems to know what the dishy to ground station actually
is, although a lot of folk seem to be speculating it is mpls, my bet
is still something custom that has a destination and encrypted
payload....
> My traceroute [v0.95]
> 123-1234567.local (192.168.42.229) -> www.heise.de (193.99.144.85) 2023-08-30T21:39:48+0200
> Keys: Help Display mode Restart statistics Order of fields quit
> Packets Pings
> Host Loss% Snt Last Avg Best Wrst StDev
> 1. AS??? 192.168.42.1 (192.168.42.1) 0.0% 1067 0.9 0.6 0.5 9.1 0.4
> 2. AS6805 loopback1.0003.acln.06.ham.de.net.telefonica.de (62.52.201.200) 0.0% 1067 12.3 22.5 9.9 172.7 17.5
> 3. AS6805 bundle-ether10.0002.dbrx.06.ham.de.net.telefonica.de (62.53.2.98) 0.7% 1067 12.4 12.0 10.3 16.5 0.7
> 4. AS6805 ae7-0.0001.corx.06.ham.de.net.telefonica.de (62.53.15.0) 0.0% 1067 18.7 19.2 17.2 48.9 2.4
> [MPLS: Lbl 16624 TC 0 S 1 TTL 1]
> 5. AS6805 ae6-0.0002.corx.02.fra.de.net.telefonica.de (62.53.0.49) 0.0% 1067 41.6 19.6 17.2 51.6 3.9
> [MPLS: Lbl 16624 TC 0 S 1 TTL 1]
> 6. AS6805 bundle-ether2.0001.cord.01.off.de.net.telefonica.de (62.53.0.199) 0.0% 1067 19.0 19.3 17.7 87.1 2.2
> [MPLS: Lbl 16624 TC 0 S 1 TTL 1]
> 7. AS6805 bundle-ether1.0002.corp.01.off.de.net.telefonica.de (62.53.28.171) 0.0% 1067 22.9 19.2 17.5 29.7 0.9
> 8. AS??? ipv4.de-cix.fra.de.as12306.plusline.net (80.81.192.132) 0.0% 1066 18.5 19.7 18.2 93.0 2.5
> 9. AS12306 82.98.102.71 (82.98.102.71) 0.0% 1066 19.6 19.4 17.7 69.5 1.7
> [MPLS: Lbl 24002 TC 0 S 1 TTL 1]
> 10. AS12306 82.98.102.23 (82.98.102.23) 0.0% 1066 17.8 19.8 17.4 197.7 9.9
> 11. AS12306 212.19.61.13 (212.19.61.13) 0.0% 1066 19.8 19.6 17.5 155.7 6.1
> 12. AS12306 www.heise.de (193.99.144.85) 0.1% 1066 19.6 19.1 17.6 63.7 1.5
>
> Not that these do not already stick out as hops at different locations (here Hamburg (ham), Frankfurt (fra) and Offenbach)) all with more or less identical distance-independent RTTs.
>
> Other than that quite intriguing puzzle, I wonder whether we could teach flent to run a bidirectional traceroute/mtr as part of its measurements..?
>
> Regards
> Sebastian
>
>
> > On Aug 30, 2023, at 20:07, Dave Taht via Starlink <starlink at lists.bufferbloat.net> wrote:
> >
> > 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. 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....
> >
> >
> > --
> > Oct 30: https://netdevconf.info/0x17/news/the-maestro-and-the-music-bof.html
> > Dave Täht CSO, LibreQos
> > <thestarlinkmystery.png>_______________________________________________
> > Starlink mailing list
> > Starlink at lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/starlink
>
--
Oct 30: https://netdevconf.info/0x17/news/the-maestro-and-the-music-bof.html
Dave Täht CSO, LibreQos
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