From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from vsmx002.dclux.xion.oxcs.net (vsmx002.dclux.xion.oxcs.net [185.74.65.108]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 887343B29E for ; Tue, 26 Oct 2021 09:49:51 -0400 (EDT) Received: from proxy-2.proxy.oxio.ns.xion.oxcs.net (proxy-2.proxy.oxio.ns.xion.oxcs.net [41.90.113.162]) by mx-out.dclux.xion.oxcs.net (Postfix) with SMTP id 2F91B8C0432; Tue, 26 Oct 2021 13:49:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=dclux.xion.oxcs.net; s=mail1; t=1635256190; bh=mmYjtUwH6KeMwh3XaNlRL1qdK60RM+nPoG4hwKcGIvE=; h=Date:From:To:Cc:In-Reply-To:References:Subject:From; b=txcV9xVZyAUc8VN7UwlwWqtlCUgIgc2wTsP/5vRR3hScY/qcP5NmQ/gQe7rb3wbxO rPBmO7iG4EJovJjXYbywyPyUjdmuMvYFL3fg8+hLvrsL4WaWxXPA0eYNkwPJBJj1VR AnUBtNxfCLgKGno0rEMMkh1rh/8IxB+jdZQzDTWEhggeZnQIDktuG+xcfIVF2rOnLg np4dS7pr1y2JKWofZHBvBlzx0+vBjfv9iYBNXGAvZkPeh3jdMckOkj5k8FKrCF+OJw F8Rw/LrE9kHW508w1SvNp0Yp4qXO8mWOh9x84KmKK816gbQk9l6PqGGyNx5/14YDbu FQJwGVg7XhYHQ== Date: Tue, 26 Oct 2021 16:49:37 +0300 From: Mike Puchol To: starlink@lists.bufferbloat.net, Dave Taht Cc: Mark Handley Message-ID: In-Reply-To: References: X-Readdle-Message-ID: e6088411-1d1f-46e6-ba08-46bfe4c6b669@Spark MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="61780777_15b5af5c_28c9" X-VadeSecure-Status: LEGIT X-VADE-STATUS: LEGIT Subject: Re: [Starlink] thinking about the laser links again X-BeenThere: starlink@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Starlink has bufferbloat. Bad." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 26 Oct 2021 13:49:51 -0000 --61780777_15b5af5c_28c9 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Heya, My 2 cents - I have some experience with ground-based =46SOC links, so I = can take educated guesses at what they may be able to achieve. The laser links, as far as I know, will be able to do in-plane and cross-= plane (e.g. between satellites in front and behind in the orbit, or acros= s to the sides). This gives a great level of flexibility, but also compli= cates the system as you now need a rotating head or full gimbal. Ground-based =46SOC links have a scan time that can range from a few seco= nds to a few minutes, depending on how long a link has been lost, and the= y all must begin with a fairly accurate idea of where you are pointed. Se= tting up a link to a satellite that is more or less static, in front or b= ehind, is relatively easy. If you link is lost, you can re-establish fair= ly quickly. Across planes on the same shell, the positions are almost static too, so = the same rules apply. =46rom photos, each satellite carries two optical h= eads, thus IMHO the first generation will link in-plane only, to keep thi= ngs simple. To do both in-plane and cross-plane, you need at least three = optical heads. Once you add more shells, the problems begin. Optical links work in micro= radians (0.0000572=C2=BA, your brain needs to adapt to these new scales=E2= =80=A6), so when satellites across planes could have relative velocities = in the degrees per second, a laser link will have a real hard time to sca= n for the other site. I could bore you to death but here=E2=80=99s a quick test you can do: gra= b a laser pointer and try to keep it on a target the size of the laser do= t on a wall 10-15 meters away. You=E2=80=99ll quickly see why doing that = at hundreds of kilometers, and between moving vehicles, is a real challen= ge. The logical thing to start with would be to keep every shell interconnect= ed, but not to try to cross-link shells. =46or this, ground-to-satellite = links come into play. How do you make capacities in the petabits per second around your space s= egment useful=3F You need to deliver to the ground eventually. IMHO the o= nly way this will hapen is ground-to-satellite links, with the ground sta= tions either in a few, as cloudless as possible locations, or many statio= ns in as geographically diverse configuration as possible, so that at lea= st some will not have cloud cover. Once you have the ground links to each shell, they can be used to offload= to internet backbones, or you can relay data between shells, without com= plicating your pointing & tracking on the satellites. I think Dave has a point in that a very obvious use is H=46T and the like= , as the latencies will be way way lower than what you could achieve with= ground fiber. Mark Handley makes a very good job at explaining in this video (and other= s he has posted):=C2=A0https://www.youtube.com/watch=3Fv=3DQEIUdMiColU Best, Mike On Oct 26, 2021, 04:26 +0300, Dave Taht , wrote: > I haven't really been focused on the starlink stuff for many months, > although I do periodically run a test to see if they've fixed their > bufferbloat anywhere. (nope). The networkQuality test from apple is > now shipping in OSX=21=21 and I can think about something else. > > I'd written this, I guess, over 2 years ago: > https://www.reddit.com/r/Starlink/comments/brn6gg/will=5Fstarlink=5Fhav= e=5Fbufferbloat/ > > and had had a nice dialog with mark handley (who has since stopped > writing anything about starlink so I kind of assume he went under NDA) > > At the time I first started thinking about this I had had a few > objections to his simulations. One was that he made the assumption in > his earliest simulations that the sats would be routing =22up there=22 > rather than down here. The first sats routed simply to the next hop or > a failover hop and that is easy to think about (and the congestion > problems soluble with the tools already developed by the bufferbloat > project). His later sims did that, but neither set seemed to address > congestion control issues. > > Now that the first laser sats are launching, thinking about how that > would work, in the dearth of other information, is hard. One number I > don't have is what the actual capacity is for each laser link > (anyone=3F), and for how long. I'd also thought at the time I'd written= > the above that the value of going new york to tokyo primarily by > satellite was a license to print money. The value of that path seemed > to be in the millions/minute range - so I had generally assumed that > usage of it would be governed by a virtual circuit setup, used > internally, or by major governments, or investment houses. It made the > most sense to me to terminate most links back to the ground as quickly > as possible, otherwise. > > But in thinking about 33,000 sats... rather than the paltry (cough) > few they've presently flown, as a giant LAG switch that can cross > oceans, I can certainly see the concept being used for more general > purpose traffic especially to the islands of the world. That gets me > to my second question: of the field of view of the sat links=3F > > And then my humdinger question based on their launch schedule and > satellite distribution... how long before they can get a first transit > from new york (or london) to tokyo, borne entirely on the sat laser > links themselves=3F It needn't be direct, just taking advantage of the > known satellite laser links to get that far. > > > -- > =46ixing Starlink's Latencies: https://www.youtube.com/watch=3Fv=3Dc9gL= o6Xrwgw > > Dave T=C3=A4ht CEO, TekLibre, LLC > =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F > Starlink mailing list > Starlink=40lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink --61780777_15b5af5c_28c9 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
Heya,

My 2 cents - I have some experience with ground-based =46SOC links, so I = can take educated guesses at what they may be able to achieve.

The laser links, as far as I know, will be able to do in-plane and cross-= plane (e.g. between satellites in front and behind in the orbit, or acros= s to the sides). This gives a great level of flexibility, but also compli= cates the system as you now need a rotating head or full gimbal.&=23160;<= br />
Ground-based =46SOC links have a scan time that can range from a few seco= nds to a few minutes, depending on how long a link has been lost, and the= y all must begin with a fairly accurate idea of where you are pointed. Se= tting up a link to a satellite that is more or less static, in front or b= ehind, is relatively easy. If you link is lost, you can re-establish fair= ly quickly.

Across planes on the same shell, the positions are almost static too, so = the same rules apply. =46rom photos, each satellite carries two optical h= eads, thus IMHO the first generation will link in-plane only, to keep thi= ngs simple. To do both in-plane and cross-plane, you need at least three = optical heads.

Once you add more shells, the problems begin. Optical links work in micro= radians (0.0000572=C2=BA, your brain needs to adapt to these new scales=E2= =80=A6), so when satellites across planes could have relative velocities = in the degrees per second, a laser link will have a real hard time to sca= n for the other site.

I could bore you to death but here=E2=80=99s a quick test you can do: gra= b a laser pointer and try to keep it on a target the size of the laser do= t on a wall 10-15 meters away. You=E2=80=99ll quickly see why doing that = at hundreds of kilometers, and between moving vehicles, is a real challen= ge.

The logical thing to start with would be to keep every shell interconnect= ed, but not to try to cross-link shells. =46or this, ground-to-satellite = links come into play.

How do you make capacities in the petabits per second around your space s= egment useful=3F You need to deliver to the ground eventually. IMHO the o= nly way this will hapen is ground-to-satellite links, with the ground sta= tions either in a few, as cloudless as possible locations, or many statio= ns in as geographically diverse configuration as possible, so that at lea= st some will not have cloud cover.

Once you have the ground links to each shell, they can be used to offload= to internet backbones, or you can relay data between shells, without com= plicating your pointing & tracking on the satellites.

I think Dave has a point in that a very obvious use is H=46T and the like= , as the latencies will be way way lower than what you could achieve with= ground fiber.

Mark Handley makes a very good job at explaining in this video (and other= s he has posted):&=23160;https://www.youtube.com/watch=3Fv=3D= QEIUdMiColU

Best,

Mike
On Oct 26, 2021, 04:26 +0300, Dave = Taht <dave.taht=40gmail.com>, wrote:
I haven't really been focused on the starlink stuff for many mo= nths,
although I do periodically run a test to see if they've fixed their
= bufferbloat anywhere. (nope). The networkQuality test from apple is
= now shipping in OSX=21=21 and I can think about something else.

I'd written this, I guess, over 2 years ago:
https://www.reddit.com/r/Starlink/comments/brn6gg/will=5Fstarlink=5Fhave=5F= bufferbloat/

and had had a nice dialog with mark handley (who has since stopped
writing anything about starlink so I kind of assume he went under NDA)
At the time I first started thinking about this I had had a few
objections to his simulations. One was that he made the assumption in
his earliest simulations that the sats would be routing =22up there=22 rather than down here. The first sats routed simply to the next hop or a failover hop and that is easy to think about (and the congestion
problems soluble with the tools already developed by the bufferbloat
project). His later sims did that, but neither set seemed to address
congestion control issues.

Now that the first laser sats are launching, thinking about how that
would work, in the dearth of other information, is hard. One number I
don't have is what the actual capacity is for each laser link
(anyone=3F), and for how long. I'd also thought at the time I'd written the above that the value of going new york to tokyo primarily by
satellite was a license to print money. The value of that path seemed
to be in the millions/minute range - so I had generally assumed that
usage of it would be governed by a virtual circuit setup, used
internally, or by major governments, or investment houses. It made the most sense to me to terminate most links back to the ground as quickly as possible, otherwise.

But in thinking about 33,000 sats... rather than the paltry (cough)
= few they've presently flown, as a giant LAG switch that can cross
oceans, I can certainly see the concept being used for more general
= purpose traffic especially to the islands of the world. That gets me
to my second question: of the field of view of the sat links=3F

And then my humdinger question based on their launch schedule and
satellite distribution... how long before they can get a first transit from new york (or london) to tokyo, borne entirely on the sat laser
= links themselves=3F It needn't be direct, just taking advantage of the known satellite laser links to get that far.


--
=46ixing Starlink's Latencies: https://www.youtube.com/watch=3Fv=3Dc9gLo6= Xrwgw

Dave T=C3=A4ht CEO, TekLibre, LLC
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F
Starlink mailing list
Starlink=40lists.bufferbloat.net
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