From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-x529.google.com (mail-pg1-x529.google.com [IPv6:2607:f8b0:4864:20::529]) (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 200423CB37 for ; Sat, 2 Mar 2024 12:26:34 -0500 (EST) Received: by mail-pg1-x529.google.com with SMTP id 41be03b00d2f7-5c229dabbb6so2048480a12.0 for ; Sat, 02 Mar 2024 09:26:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1709400393; x=1710005193; darn=lists.bufferbloat.net; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=irzq/Esee6LYe1+zcoA/JupTxZZ0GadWe6VhFkbiPB8=; b=mFiPm2X+8FyvB1gf8ng4d3aa78M4MDjdWgYbfxtv6OFIlWMwE74jFPjT64/EPpruIh ukMTOKqo6pdb2drE/iWn3eY+yI0Y7002ee+YkX9WjHFflKCSnJf4nFyoEEg1VoS1PfPy hcjKiYQag0B3NwmYXCoOsukSPTNcBViTC76P7pWAUAl3DRFEJAfi/BEb/TTfrEqeh8jq YXjEr06IduxqZydcI2MILKZEPTjuWt7PkcbykDP0l/4+9RHwx1c8oWnUJL8ykrc9C7qw pqIkNFHabnKhuAD0MRYiM3pX6z+SgmFErNhP3vDBkqMII1hOJ88sFYURWS3MHUIymrWN Iyfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709400393; x=1710005193; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=irzq/Esee6LYe1+zcoA/JupTxZZ0GadWe6VhFkbiPB8=; b=HD1UZrk4rBYGsC1qeiv8M56aflC1BKBn3TqVYqvEHg0xOxUfTIudnAUNYhr5n90FpI 9TsVA6sLIGbc0rUMWPUd7705N0gwgYO65X0OPBpsLlbe/BD0Dj4Nl2Yja+PEKr18fbMr NNPWMLKZTEWLka1Y+lSxKHfTekYx+rcWwU/wWnDiqA6lJ3PwrXQuSju9EOyhpCaWXRi5 OjJQtC/d/3VnSx8ymyLGCCWz1qCzMN0UdgUSfsEpToNcCCEjP1d9B0TkvB5r/P9dGgkS M72NAawa/Vj0zgoYb6UOaGBZzOH3K7ZwrKu9r3GOkwbBPm/YzZgekhRc6c6C8RKSwBim yWAA== X-Gm-Message-State: AOJu0YyUTKa1Iozz3sjBNP/ZozBRL9IXsuTJ0x7H/2WmHupax1891WmF 2B9To/Audp24X48kLTu6lekPEeBUR28I+1JklEvpwtRvfxQ7hzab6n/hrIN4LjgtVLBGwD1raUg dfD5jx9wdtGJUBIHlkRNSHEg1Bxc= X-Google-Smtp-Source: AGHT+IE5DVEHHb6PI9JEr5toHaMvrH4/plsCO2HE0vTmxVMo6nO+nDdwgHneZqVr6a5Z5bGTwBv9B0fuHbsP0kLDqmo= X-Received: by 2002:a17:90a:cb94:b0:29b:171c:a787 with SMTP id a20-20020a17090acb9400b0029b171ca787mr3860839pju.19.1709400392864; Sat, 02 Mar 2024 09:26:32 -0800 (PST) MIME-Version: 1.0 References: <9a4e1bb4-0591-40f7-b072-8a1abd60f315@gmail.com> <46eccea2-0fbd-46df-b0cc-70691d4a75f4@gmail.com> In-Reply-To: <46eccea2-0fbd-46df-b0cc-70691d4a75f4@gmail.com> From: Hesham ElBakoury Date: Sat, 2 Mar 2024 09:26:18 -0800 Message-ID: To: Alexandre Petrescu Cc: Dave Taht via Starlink Content-Type: multipart/alternative; boundary="000000000000321fde0612b0cb5f" 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: Sat, 02 Mar 2024 17:26:34 -0000 --000000000000321fde0612b0cb5f Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable But how you address the issues I mentioned before such propagation delay, clock drifting, and signal degradation, ... Hesham On Sat, Mar 2, 2024, 9:18 AM Alexandre Petrescu via Starlink < starlink@lists.bufferbloat.net> wrote: > some of the question is to what level of precision one wants the time to > be maintained synchronized between entities, and for what application? > Nano-second precision? Less? More is acceptable? For what kind of > application? (I will not give examples). > > I think links with hundred ms latency range and NTP can easily maintain > nano-second synch'ed precision, from experience with ground links. > > > Le 02/03/2024 =C3=A0 18:01, Alexandre Petrescu via Starlink a =C3=A9crit = : > > > > Le 02/03/2024 =C3=A0 16:38, Christian von der Ropp via Starlink a =C3= =A9crit : > >> Why not acquire the time directly from by the satellite terminal and > >> run local NTP servers instead of syncing via the Internet? > > > > Certainly it is possible to run ntpd servers and clients on satellites > > and maintain synchronized times. I would be surprised if some of them > > dont already do that. > > > > The performance characteristics of some links between some satellites > > are not very different than links here on ground where NTP is run > > routinely. > > > > NTP was designed and tested at a time when ground links had inferior > > perf. characteristics than many satcom links of recent years. > > > > Alex > > > > > >> 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. > >> > >> > >> Am 2. M=C3=A4rz 2024 17:25:59 OEZ schrieb Hesham ElBakoury via Starlin= k > >> : > >> > >> 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? > >> > >> Thanks > >> Hesham > >> > >> On Sat, Mar 2, 2024, 7:18 AM Sebastian Moeller > >> wrote: > >> > >> Hi Hesham > >> > >> > On 2. Mar 2024, at 16:03, Hesham ElBakoury via Starlink > >> wrote: > >> > > >> > 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, > >> > >> [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. > >> > >> > satellite communication involves signals traveling vast > >> distances through space. This creates significant delays. > >> > >> [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... > >> > >> > 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. > >> > 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 > >> > > >> > > >> > > >> > _______________________________________________ > >> > Starlink mailing list > >> > Starlink@lists.bufferbloat.net > >> > https://lists.bufferbloat.net/listinfo/starlink > >> > >> -- > >> Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail > >> gesendet. > >> > >> _______________________________________________ > >> 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 > _______________________________________________ > Starlink mailing list > Starlink@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink > --000000000000321fde0612b0cb5f Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
But how you address the issues I mentioned before such pr= opagation delay, clock drifting, and signal degradation, ...

Hesham

On Sat, Mar 2, 2024, 9:18 AM Ale= xandre Petrescu via Starlink <starlink@lists.bufferbloat.net> wrote:
some of the question is to what level of precision one w= ants the time to
be maintained synchronized between entities, and for what application?
Nano-second precision?=C2=A0 Less?=C2=A0 More is acceptable?=C2=A0 For what= kind of
application?=C2=A0 (I will not give examples).

I think links with hundred ms latency range and NTP can easily maintain nano-second synch'ed precision, from experience with ground links.


Le 02/03/2024 =C3=A0 18:01, Alexandre Petrescu via Starlink a =C3=A9crit=C2= =A0:
>
> Le 02/03/2024 =C3=A0 16:38, Christian von der Ropp via Starlink a =C3= =A9crit=C2=A0:
>> Why not acquire the time directly from by the satellite terminal a= nd
>> run local NTP servers instead of syncing via the Internet?
>
> Certainly it is possible to run ntpd servers and clients on satellites=
> and maintain synchronized times.=C2=A0 I would be surprised if some of= them
> dont already do that.
>
> The performance characteristics of some links between some satellites =
> are not very different than links here on ground where NTP is run
> routinely.
>
> NTP was designed and tested at a time when ground links had inferior <= br> > perf. characteristics than many satcom links of recent years.
>
> Alex
>
>
>> LEO satellite terminals always have onboard GNSS antennas for
>> geolocation which is necessary to find the satellites, so integrat= ing
>> a local GNSS-disciplined Stratum-1 NTP server seems trivial to me.=
>>
>>
>> Am 2. M=C3=A4rz 2024 17:25:59 OEZ schrieb Hesham ElBakoury via Sta= rlink
>> <starlink@lists.bufferbloat.net>:
>>
>> =C2=A0=C2=A0=C2=A0 Hi=C2=A0Sebastian,
>> =C2=A0=C2=A0=C2=A0 Can we still use PTP and NTP for time synchroni= zation in
>> =C2=A0=C2=A0=C2=A0 Satellite networks or we need new protocols? If= we need new
>> =C2=A0=C2=A0=C2=A0 protocols, do such protocols exist?
>>
>> =C2=A0=C2=A0=C2=A0 Thanks
>> =C2=A0=C2=A0=C2=A0 Hesham
>>
>> =C2=A0=C2=A0=C2=A0 On Sat, Mar 2, 2024, 7:18 AM Sebastian Moeller = <moeller0@gmx.de>
>> =C2=A0=C2=A0=C2=A0 wrote:
>>
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Hi Hesham
>>
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > On 2. Mar 2024, at= 16:03, Hesham ElBakoury via Starlink
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 <starlin= k@lists.bufferbloat.net> wrote:
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 >
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > Time synchronizati= on, for satellite networks, faces several
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 challenges:
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > 1. Signal Propagat= ion Delays: Unlike terrestrial networks
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 where signals travel th= rough cables at the speed of light,
>>
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 [SM] The speed of light= in your typical glas fibers (and
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 accidentally the inform= ation propagation speed in metallic
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 conductors) comes in ro= ughly at 2/3 of the speed of light in
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 vacuum, while the speed= of light in air at see level is a mere
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 90 KM/s slower than in = vacuum.
>>
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > satellite communic= ation involves signals traveling vast
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 distances through space= . This creates significant delays.
>>
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 [SM] Sure distances mig= ht be larger, but propagation speed is
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 around 100000Km/s faste= r... my main point is speed of light is
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 a) dependent on the med= ium b) not the things that
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 differentiates space fr= om the earth's surface here, but mere
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 geometry and larger dis= tances on larger spheres...
>>
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > 2. Clock Drift: Ev= en highly precise atomic clocks, used in
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 satellites, are suscept= ible to "drift" - gradually losing or
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 gaining time. This drif= t, caused by factors like temperature
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 variations, radiation e= xposure, and power fluctuations, can
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 lead to inconsistencies= in timekeeping across the network.
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > 3. Signal Degradat= ion: As signals travel through space, they
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 can degrade due to fact= ors like atmospheric interference,
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ionospheric disturbance= s, and solar activity. This degradation
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 can introduce noise and= errors, impacting the accuracy of time
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 synchronization message= s.
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > 4. Limited Resourc= es: Satellites have limited power and
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 processing capabilities= . Implementing complex synchronization
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 protocols can be resour= ce-intensive, requiring careful
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 optimization to minimiz= e their impact on other functionalities.
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > 5. Evolving Techno= logies: As satellite technologies and
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 applications continue t= o evolve, new challenges related to
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 synchronization might e= merge. For example, the integration of
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 constellations with tho= usands of satellites poses unique
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 synchronization challen= ges due to the sheer scale and
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 complexity of the netwo= rk.
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > These challenges n= ecessitate the development of robust and
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 efficient time synchron= ization protocols for satellite
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 networks and an integra= ted satellite and terrestrial networks
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > Are you aware of s= uch time synchronization protocols?
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > I would think that= using Satellite simulators is the most
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 viable way to develop a= nd test these protocols given that
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 using satellites is not= that easy.
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > Thanks
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > Hesham
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 >
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 >
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 >
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > __________________= _____________________________
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > Starlink mailing l= ist
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > Starli= nk@lists.bufferbloat.net
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > https://lists.bufferbloat.net/listinfo/starlink
>>
>> --
>> Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail=
>> gesendet.
>>
>> _______________________________________________
>> Starlink mailing list
>> Starlink@lists.bufferbloat.net
>> https://lists.bufferbloat.net/lis= tinfo/starlink
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinf= o/starlink
_______________________________________________
Starlink mailing list
Starlink@lists.bufferbloat.net
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