From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.15.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 1C1FA3B29D for ; Mon, 1 Apr 2024 18:22:23 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.de; s=s31663417; t=1712010142; x=1712614942; i=moeller0@gmx.de; bh=QyV1qzvlxSRXcjUOqj0LxHgLIcNKD/wuEvsP55cuzJM=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References: To; b=kV+aKJlTWdpCsz1GoA03m+boDMslNSyVMHAynb6b0O17O5qU9zItkv3UsAUGqBvT Rzfd4rk4YSmF5Pdkb+WSmLzYdu5hXayyIISmnZEpIKznj46OvbtoZ4vO3lvaEt9dj 1p7xBDZcW41D12AfplB29Q3yQrVeJoxSeNUoK940BxF67UE7s7+uneLpSWvAH7J84 KeKr6ZJEduHBGRmhufHh8sY+I6qhnIGUumQiDDqCnPWdkpffIXQQJs8yeGDnU9Jsr 3e80mWmpiqlqEPBKjORIiOSsz3c++geKsBF0j9tRpYNamsGYkiS5SWlDK5QvLx4gS NBYKZ6EC6nHQCXMfCQ== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from smtpclient.apple ([77.1.55.8]) by mail.gmx.net (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1MMobO-1sABuk0zx6-00Ihp5; Tue, 02 Apr 2024 00:22:22 +0200 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3774.500.171.1.1\)) From: Sebastian Moeller In-Reply-To: Date: Tue, 2 Apr 2024 00:22:11 +0200 Cc: Christian von der Ropp , Hesham ElBakoury via Starlink Content-Transfer-Encoding: quoted-printable Message-Id: <79F8B638-D4B0-4052-AE1C-FC8F4BD75D4D@gmx.de> References: <1C8781A0-8AFF-4118-B410-D1DB66000F18@vdr.net> To: Hesham ElBakoury X-Mailer: Apple Mail (2.3774.500.171.1.1) X-Provags-ID: V03:K1:Z5jzORXDVNx3aHvZNyl2ZTPebrwkn8N+dYp85vUuzG4x7HyBga1 PmYJd8eYgk7xXA/4+TCQOfMIHIGXe2V+lYMs+bFyyBKfDnfc0/NOhDPYcfrIBtp3r9S3WlE NAgLo7VA1tLdadHOzPuhWk4Mb+mAs90TuQVSulc3eCwjajvQPOqfV3SOFSS7VXn6ZdpgzXp 4DxFXH5ZbbPdTGU2Z4w4A== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:93lpu6jxjus=;n7jzwl72RVwRMw98XzAV/8s1Gv6 unIIATFe6Gi6lCZS5RW+fVC2v+N1Qp1I4iYMr33JZkj1JG+6Zd1J1Po5yXPG/If4N+rZMMjhG da4pMT76p/wvlmOkcqRdau/JXWeVo9ixUQQLTMB7cnIw56lOJhNZ2yXvI3VPpRK1kx+tlJf50 w1RH13+V4a93VPQfXN5/956OF2sd7/V7d64SCWtR4sN0J3OzIMEmWam6Zxj0G47qM2jpRO4mm YVkS4ErJhiAw7xdmiXBHO5KukzLICrdE57SOS8aGRUZODSbanRhvgF9M75HVmaIoicYPctY9F HR5LGir8a5OcUD1CuLIA3T/nCLVZb43xQxa7z4Sls2w0WoE2EvhfO8nzBNK3aGO2o76axFf/g frvbX8yWyVz1Llt2gkan93JiQ6hTsqyccwjbGdHvFY8JoJdKk2Bj4LJOXOxLYsb/bLzlIexxa qBJyEEEehfH4cl5/XRHAnlPdZEHB7SIYQgY2XJVRA8qez5oAUpMeyF/krR+vvQX2hL0JHU1Jb 7VELs1LGBTeWBQZumQimjc+uCwxmgtyLC9byxzxiqz9MjtTDKcyyCKiw0BqO5KX1GGMz6f7bR 3W89FG8Ej7TVtpIWEWW24yft8cy9wsUe8MOXXlU18U6aEppCSz7VCkX+2ZXjWua/YEu2f/fNr piOjTyNgUPbkiTELLJSLHd+yaK7u+gaqGVErTJPJsqgFTAlZR9EsnpWnvOTlRCRqMil9IcNHR zt2xFyy+sa4Bz6fCt7mDwGjV/WsKafS8Em1MpWF+gpiaZC54LD9aYSviWxvBPykd2vQ9XRjcu fakIlRobL6vxHpqg8zHBplMCFiYWMcCjG/MPhwEpLmQvY= Subject: Re: [Starlink] Time Synchronization in Satellite Networks 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: Mon, 01 Apr 2024 22:22:24 -0000 Hi Hesham, > On 2. Apr 2024, at 00:04, Hesham ElBakoury = wrote: >=20 > Hi Christian, > The problems is that Satellites move, therefore, the delay between = the different directions is different which violates the condition to = run NTP and PTP.=20 But GPS Satellites themselves are not in geostationary oprbit, and still = we can get precision time from them... so I would argue that must be a = solved problem, no? Regards Sebastian >=20 > Hesham >=20 > On Sat, Mar 2, 2024, 8:19 AM Christian von der Ropp = wrote: > Hi Hesham, >=20 > You do not acquire the time from a LEO satellite but directly from the = GPS satellites which carry an atomic clock on board. > I'd not be aware of any LEO providing a GNSS signal but Xona plan such = system (although not carrying proper atomic clocks but probably = chip-sized atomic clocks that require frequent syncing with proper = atomic clocks): > https://twitter.com/Megaconstellati/status/1708091536439673323 >=20 > There are efforts to build trapped-ion quantum clocks that are = expected to become significantly smaller and cheaper than traditional = atomic clocks while as accurate which would make it viable to put an = atomic clock-equivalent on small LEO satellites. Once that happens you = would have an independent alternative to the big GNSS birds in MEO but = with stronger signals. I'm told that we are 5-10 years away from such = trapped-ion quantum clocks. >=20 > But for NTP clients, the described method (running a local NTP server = in the satellite terminal synced to GPS) should be good enough. >=20 > Christian >=20 >=20 > Am 2. M=C3=A4rz 2024 18:02:47 OEZ schrieb Hesham ElBakoury = : > Hi Christian, > How you synchronize the time of the satellites in the network? Are you = saying each satellite has a master clock? >=20 > Hesham >=20 > On Sat, Mar 2, 2024, 7:38 AM Christian von der Ropp = wrote: > Why not acquire the time directly from by the satellite terminal and = run local NTP servers instead of syncing via the Internet? LEO satellite = terminals always have onboard GNSS antennas for geolocation which is = necessary to find the satellites, so integrating a local = GNSS-disciplined Stratum-1 NTP server seems trivial to me. >=20 >=20 > Am 2. M=C3=A4rz 2024 17:25:59 OEZ schrieb Hesham ElBakoury via = Starlink : > Hi Sebastian, > Can we still use PTP and NTP for time synchronization in Satellite = networks or we need new protocols? If we need new protocols, do such = protocols exist? >=20 > Thanks > Hesham >=20 > On Sat, Mar 2, 2024, 7:18 AM Sebastian Moeller = wrote: > Hi Hesham >=20 > > On 2. Mar 2024, at 16:03, Hesham ElBakoury via Starlink = wrote: > >=20 > > Time synchronization, for satellite networks, faces several = challenges: > > 1. Signal Propagation Delays: Unlike terrestrial networks where = signals travel through cables at the speed of light, >=20 > [SM] The speed of light in your typical glas fibers (and accidentally = the information propagation speed in metallic conductors) comes in = roughly at 2/3 of the speed of light in vacuum, while the speed of light = in air at see level is a mere 90 KM/s slower than in vacuum.=20 >=20 > > satellite communication involves signals traveling vast distances = through space. This creates significant delays. >=20 > [SM] Sure distances might be larger, but propagation speed is around = 100000Km/s faster... my main point is speed of light is a) dependent on = the medium b) not the things that differentiates space from the earth's = surface here, but mere geometry and larger distances on larger = spheres... >=20 > > 2. Clock Drift: Even highly precise atomic clocks, used in = satellites, are susceptible to "drift" - gradually losing or gaining = time. This drift, caused by factors like temperature variations, = radiation exposure, and power fluctuations, can lead to inconsistencies = in timekeeping across the network. > > 3. Signal Degradation: As signals travel through space, they can = degrade due to factors like atmospheric interference, ionospheric = disturbances, and solar activity. This degradation can introduce noise = and errors, impacting the accuracy of time synchronization messages.=20 > > 4. Limited Resources: Satellites have limited power and processing = capabilities. Implementing complex synchronization protocols can be = resource-intensive, requiring careful optimization to minimize their = impact on other functionalities. > > 5. Evolving Technologies: As satellite technologies and applications = continue to evolve, new challenges related to synchronization might = emerge. For example, the integration of constellations with thousands of = satellites poses unique synchronization challenges due to the sheer = scale and complexity of the network. > > These challenges necessitate the development of robust and efficient = time synchronization protocols for satellite networks and an integrated = satellite and terrestrial networks > > Are you aware of such time synchronization protocols? > > I would think that using Satellite simulators is the most viable way = to develop and test these protocols given that using satellites is not = that easy. > > Thanks > > Hesham > >=20 > >=20 > >=20 > > _______________________________________________ > > Starlink mailing list > > Starlink@lists.bufferbloat.net > > https://lists.bufferbloat.net/listinfo/starlink >=20 > --=20 > Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail = gesendet. > --=20 > Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail = gesendet.