From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-il1-x12a.google.com (mail-il1-x12a.google.com [IPv6:2607:f8b0:4864:20::12a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 04FE73B2A4 for ; Thu, 28 Oct 2021 21:12:28 -0400 (EDT) Received: by mail-il1-x12a.google.com with SMTP id l13so8985676ilh.3 for ; Thu, 28 Oct 2021 18:12:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=eW2Guw3Ii3H/x+uDq2XGUcF6Wu0/epbtGeoH/yJL6oQ=; b=UuZSLNavBxWlGgWTprRosoiA1gcaC5i9f+ZP944U8LSuFfYrXcZhvCnX4hDzM/J3a6 aNeoDbdIFzS3anlvg+gOIAAKZSYJM7KHsHaZ25QMADRnT36Gz04H77a4Wq+hzRR8LrMc MKKyG7hyVBkCHYSH98NOrHzN4jtZFsp6RwZw7bRezXZQ56UFyw5bMBz6RBwr1ll3U6Bf 3W3tpb+BkA9B3QwbqXK5iAwPE4wF/jjwPBPyoBr2cYGr1lazfoGCWgUa5ZjaJy55NKW+ byJ+AjisjmLfsO5GlCnnfG8njkS/VcLSb50IYTgFH/5neEDAScfKOWRNu56VfX0OUQ1E Icvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=eW2Guw3Ii3H/x+uDq2XGUcF6Wu0/epbtGeoH/yJL6oQ=; b=CBekduWUeJ5qdHAu6VvBZRW/Kta3n9R6hqfJKSmmPNA+DVqCRVEfhUxieNh4kmJ58t erXILW2Vp5/HAmpVn4OUHiEFKI83JmS9PXhN7Oi1yEiiTMyY8ndd0uhGOijpOI8fFvz6 o7EIS8dTaPmoJ4O0NNIY2HLY5QFQHMhF9z+8hnXvu1ibZvL18VJxaUBWlBg3Hx+hxz4z j2ossdj04OlHNcyWDJrV3B7EcRs91Z7VhXydlKIn6uwDzXCYFzXNdut7G+hb8C8hsJ+h bHLExnlxNkd2/Q1RN4Hwik7wYEGxHxl7Uoiy3w0DeDvNrc9q2BTsv/ZT1haEYbrsGp1A WQpw== X-Gm-Message-State: AOAM530ksOjeDal+UDocHjLRWpolerGfzpOUBCgRCDoOD6VG0JHThPPC 84CHSV/Ys7WorJLvMgWrykpHNRreExuxJ9ELORmVysVDBvg= X-Google-Smtp-Source: ABdhPJyOtJkzn8SVgmrwwUtG8eQuDJJAbcyu+YmlTUo2bowGMMChSVlfx0+aA9uAVzH7rb0jxOjL6Ob0KVlufZt/Yoc= X-Received: by 2002:a05:6e02:8a3:: with SMTP id a3mr5154785ilt.88.1635469948328; Thu, 28 Oct 2021 18:12:28 -0700 (PDT) MIME-Version: 1.0 References: <28034.1635270711@localhost> <8007.1635359366@localhost> In-Reply-To: From: Dave Taht Date: Thu, 28 Oct 2021 18:12:15 -0700 Message-ID: To: Mike Puchol Cc: Michael Richardson , Ulrich Speidel , starlink@lists.bufferbloat.net Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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: Fri, 29 Oct 2021 01:12:29 -0000 I spent some time today looking over the job listings for clues ( https://www.spacex.com/careers/index.html?search=3Dlinux ) BGP/ISIS keeps cropping up. It really also looks like they are inventing their own SDN along the way. And: their public BGP table has gained a bunch of ipv4/21s lately with a few users reporting a routable IP for a few days or weeks. I do hope they find a ipv4/12 somewhere or better, as I think they've discovered CGNs are not particularly fun, and their projected growth for the next year or two would be within that, (and one fantasy I harbor is they peer with a bunch of outback BGP AS holders with a "pro" service) I've been trying for a few years to get some industry interested in leveraging 240/4 (at least within their CGN for dishy to dishy comms), there's a preso on it at the upcoming ietf intarea: https://datatracker.ietf.org/doc/draft-schoen-intarea-unicast-240/ I know that's kind of a blue sky thing, but all the code has been working for years in both bsd and linux, as well as in multiple big iron routers, amazon, and in openwrt (where we tested it first). Just someone with balls and $s needs to step up to become a space RIR and try to make those addrs more routable than we already have.... Anyway, good discussion on this thread!!! but all of you failed to answer my humdinger question - *when* will they be able to route a packet from new york to tokyo over the laser links? That kind of event would be a world network latency record - right up there in significance with the first inter-imp comms oct 29 1969: https://en.wikipedia.org/wiki/ARPANET#/media/File:First-arpanet-imp-log.jp= g On Thu, Oct 28, 2021 at 3:53 AM Mike Puchol wrote: > > I cannot add more than the real experts on the networking / topology side= , but on the lasers themselves, a question was raised about multiple links.= The only way to do it economically is to use a single optical train per li= nk (includes laser TX and photon detector, mirrors, power control, attenuat= ors, etc.). > > I raised the idea of an FSOC =E2=80=9Cflashlight=E2=80=9D to what could b= e counted as people in the top 10 worldwide list of experts in the field. H= ere, a beam would be made wide enough to have multiple =E2=80=9Cclients=E2= =80=9D, as for radio sector antennas. The idea was quickly discarded for a = number of reasons, the principal being that you are spreading the photons s= o much that not enough would reach the other side, at least at any meaningf= ul distance. > > Photon detectors that could work are in the scientific instrument categor= y, thus really expensive. > > From photos, we know that each satellite has at least two lasers, so we c= an assume at least in-plane communications. > > Best, > > Mike > On Oct 28, 2021, 11:01 +0300, Ulrich Speidel , = wrote: > > On 28/10/2021 7:29 am, Michael Richardson wrote: > > I guess the real question is: have you written the Hollywood Security > Theatre > script based upon this issues, and can I play the geek that explains > this? :-) > > Sure! > > > - Tell satellites where to send packets (in something along the > > lines of a > > long header, as in AX.25 for example). Then a sending ground station > > would > > need a complete almanach of the constellation and an idea as to > > where the > > receiving ground station is, and which satellite it would use for the > downlink. Pros: The sending ground station can do all the number > > crunching on > > ground rather than space power. Cons: Header size costs bandwidth. > > > From what I understood, Starlink shipped some kind of comodity SDN capabl= e > chip. So MPLS, or SRv6 ought to be easy, costing only a few bytes > interpreted in hardware, and a path computation element on the ground > should > be able to deal with the calculation. > > It's a challenging situation perhaps because the network effectively gets > rewired every few minutes, but ground based computation should be able to > deal with the problem. > > > That presumes that the ground station has complete topology information > for the constellation, though. That includes knowing about defective > satellites and lasers etc., birds deviating from assigned orbit. > > But in principle, I can see how that could work, yes. > > > - Get the satellites to work out where stuff needs to be sent. If > > they were > > to use something like Bellman-Ford here, that would require an enormous > amount of update traffic. Dijkstra would require complete topology > information, which should in principle be computable from an > > almanach on the > > satellites. > > > I think, but I might be wrong, that there is a pattern which repeats > over and > over again. Just need to update the mapping of which satellite is in whic= h > position in the precomputed mesh. No need to send the entire mesh. > > > Of course. Bellman-Ford & Co. all assume a network without such > regularities. But you need to make use of those patterns in order to > make things possible - whether you do source or hop-to-hop routing. And > while the configuration of the network is indeed predictable at least > for the near future, it's not simply repeating over and over again. The > current constellation (if viewed in isolation) more or less runs in 95 > minute cycles. Earth rotates under the constellation, so the teleports > only return to the same position with respect to the constellation when > multiples of the length of a sidereal day coincide with multiples of 95 > minutes. Plus you may find that the Starlink constellation isn't > perfectly regular either in its pattern. > > > > -- > **************************************************************** > Dr. Ulrich Speidel > > School of Computer Science > > Room 303S.594 (City Campus) > Ph: (+64-9)-373-7599 ext. 85282 > > The University of Auckland > ulrich@cs.auckland.ac.nz > http://www.cs.auckland.ac.nz/~ulrich/ > **************************************************************** > > > > _______________________________________________ > Starlink mailing list > Starlink@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink > > _______________________________________________ > Starlink mailing list > Starlink@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink --=20 Fixing Starlink's Latencies: https://www.youtube.com/watch?v=3Dc9gLo6Xrwgw Dave T=C3=A4ht CEO, TekLibre, LLC