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<p class="MsoNormal">Dear SLP WG,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Below please see the response of the SDLS WG to our inquiry about the applicability of the USLP truncated transfer frame to SDLS. Many thanks to Gilles Moury and the SDLS WG for their prompt response and pondering on this issue.<o:p></o:p></p>
<p class="MsoNormal">My interpretation is that SLP should not prohibit the use of SDLS for the truncated frame. To that effect, I have uploaded a slightly modified new version of the proposed USLP blue book that allows for an optional Security Header and Trailer,
if the SDLS option is chosen for the truncated frame. Luckily, there is very little impact to the existing Section 6 SDLS chapter.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Please see the following URL for this Oct 28 version (which builds upon the inputs made during our meetings this week):
<b><a href="https://tinyurl.com/yxlkgy95">https://tinyurl.com/yxlkgy95</a><o:p></o:p></b></p>
<p class="MsoNormal">In addition, a draft project for the generation of USLP Blue book Version 2 has been created on the CWE and soon there will be another project for the update to the companion USLP GB.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Your comments are welcome.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For the changes I have just made as a proposal, please see:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<ol style="margin-top:0in" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo5">Updated note under 6.3.2<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo5">Annex G1.beta – addition of optional Security Header and Security Trailer<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo5">Update Figure G-1 Truncated TF
<o:p></o:p></li></ol>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best regards,<o:p></o:p></p>
<p class="MsoNormal">Greg Kazz<o:p></o:p></p>
<p class="MsoNormal">Chair SLP WG<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">Moury Gilles <Gilles.Moury@cnes.fr><br>
<b>Date: </b>Wednesday, October 28, 2020 at 11:28 AM<br>
<b>To: </b>"Kazz, Greg J (US 312B)" <greg.j.kazz@jpl.nasa.gov><br>
<b>Cc: </b>"sls-sea-dls@mailman.ccsds.org" <sls-sea-dls@mailman.ccsds.org>, "sls-slp@mailman.ccsds.org" <sls-slp@mailman.ccsds.org><br>
<b>Subject: </b>[EXTERNAL] RE: Does SDLS apply to USLP truncated transfer frame ?<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<p class="MsoNormal"><span style="color:#1F497D">Dear Greg,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Please find hereafter the summary of our discussion within the SDLS WG regarding the applicability of SDLS to USLP truncated transfer frame. Feel free to complement with your own notes/remarks:</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo2"><span style="color:#1F497D">USLP truncated transfer frames are meant to be used for sending short commands (as short as 2 octets) to the spacecraft. Those short commands are typically
hardware commands (bypassing OBSW) or immediate commands (triggering on-board procedures/sequences). Those commands are not necessarily emergency commands. They can be used during normal operations also. They are critical commands. Therefore, it is desirable
that they can benefit from SDLS security protection;</span><o:p></o:p></li></ul>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo2"><span style="color:#1F497D">SDLS minimum overhead (corresponding to TC baseline mode) is : Security Header (6 octets), Security Trailer – MAC (16 octets). This minimum overhead means
that SDLS protection as is , is only applicable to truncated frames fitting into 1 LDPC(256,512) codeblock (32 octet) : Frame header (5 octets), Sec Hdr (6 oct), MAC (16 oct), leaving 5 octet maximum for the command itself. If BCH is used on the link, using
SDLS would require several codeblocks per frame (at least 5). This can be acceptable, possibly even for emergency commands (e.g. tumbling spacecraft);</span><o:p></o:p></li></ul>
<p class="MsoListParagraph"><span style="color:#1F497D"> </span><o:p></o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo2"><span style="color:#1F497D">Reducing the overhead of SDLS would imply reducing the level of security provided by the protocol and taking into account additional constraints (number
of key invocations, number of forged attempts, …). For example, MAC could be truncated to 64-bit (minimum length with AES) and the Sec Hdr could be reduced to 4 octet (with a reduced anti-replay counter). Nevertheless, the WG concluded that it was not advisable
to design an SDLS “reduced overhead” baseline mode for this USLP truncated frame mode, because recommending a reduced security mode for critical commands is not appropriate for a standard.</span><o:p></o:p></li></ul>
<p class="MsoListParagraph"><span style="color:#1F497D"> </span><o:p></o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l2 level1 lfo2"><span style="color:#1F497D">Clear mode implementation is always an option for a given mission, although not recommended security-wise, whenever operational safety or link constraints
requires it.</span><o:p></o:p></li></ul>
<p class="MsoListParagraph"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Best regards,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Gilles</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D">Gilles MOURY</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#1F497D">
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D">CNES Toulouse</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#1F497D">
</span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>De :</b> SLS-SLP <sls-slp-bounces@mailman.ccsds.org> <b>De la part de</b> Moury Gilles<br>
<b>Envoyé :</b> mardi 27 octobre 2020 12:13<br>
<b>À :</b> Kazz, Greg J (US 312B) <greg.j.kazz@jpl.nasa.gov><br>
<b>Cc :</b> sls-sea-dls@mailman.ccsds.org; sls-slp@mailman.ccsds.org<br>
<b>Objet :</b> Re: [Sls-slp] Does SDLS apply to USLP truncated transfer frame ?<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Dear Greg,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Sorry for not being able to join the SLP meeting yesterday but I had another meeting at the same time that lasted more than scheduled.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">For the issue you raised concerning the applicability of SDLS to truncated USLP frames, I will add it to the discussion of the SDLS WG on Wednesday. My feeling is that, also security would be needed on those
emergency commands, the fact that minimum length for Security Header is something like 6 octets (TC baseline mode for SDLS) and minimum length for Security Trailer is something like 16 octets (TC baseline mode for SDLS) would make it :</span><o:p></o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo4"><span style="color:#1F497D">impossible to fit a truncated USLP Transfer Frame into a 7 octets BCH codeblock (truncated USLP Transfer Frame header is 5 octets leaving only 2 octets
for data field)</span><o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo4"><span style="color:#1F497D">only possible to fit a truncated USLP Transfer Frame into a 32 octets LDPC codeblock (leaving only 27 octets for data field – 22 octets being taken by Security
and Trailer)</span><o:p></o:p></li></ul>
<p class="MsoNormal"><span style="color:#1F497D">We will discuss it further with the SDLS WG. I do not know whether shorter Security Header and Trailer can be envisioned for those emergency commands carried in truncated USLP Transfer Frames.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">See you (virtually) this afternoon for the SLP webmeeting. I will provide input for the TM and AOS pink sheets regarding MCID/VCID validation in order to align TM/AOS with TC/USLP regarding this validation.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Best regards,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Gilles </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D">Gilles MOURY</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#1F497D">
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D">CNES Toulouse</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#1F497D">
</span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>De :</b> Kazz, Greg J (US 312B) <<a href="mailto:greg.j.kazz@jpl.nasa.gov">greg.j.kazz@jpl.nasa.gov</a>>
<br>
<b>Envoyé :</b> lundi 26 octobre 2020 18:45<br>
<b>À :</b> Moury Gilles <<a href="mailto:Gilles.Moury@cnes.fr">Gilles.Moury@cne<span lang="FR">s.fr</span></a>>;
<a href="mailto:sls-sdls@mailman.ccsds.org">sls-sdls@mailman.ccsds.org</a><br>
<b>Cc :</b> Kazz, Greg J (US 312B) via SLS-SLP <<a href="mailto:sls-slp@mailman.ccsds.org">sls-slp@mailman.ccsds.org</a>><br>
<b>Objet :</b> Does SDLS apply to USLP truncated transfer frame ?<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Dear Gilles and SLDS WG,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">SLP WG has a question regarding the application of the SDLS protocol to truncated USLP Transfer Frames.<o:p></o:p></p>
<p class="MsoNormal">These truncated frames are envisioned for very short length telecommands or forward link Proximity-1 link commanding. This frame type provides backward compatibility with TC hardware commands or immediate commands. These commands are typically
2 octets long. We envision the truncated USLP frame length to be between 8 and 32 octets.
<o:p></o:p></p>
<p class="MsoNormal">In that context, does it make sense for SDLS header and possibly SDLS trailer to apply to the USLP truncated frame.
<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">The discussion of the proposed non-use of SDLS for truncated USLP frames is mentioned in Chapter 6, specifically in Section 6.3.2. The definition of the truncated USLP frame is in Annex G of the attached draft document<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">The SLP WG did not think SDLS should be applicable to truncated USLP frames, but we would like your opinion on this matter.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Best regards,<o:p></o:p></p>
<p class="MsoNormal">Greg Kazz<o:p></o:p></p>
<p class="MsoNormal">Chair SLP WG<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">SLS-SLP <<a href="mailto:sls-slp-bounces@mailman.ccsds.org">sls-slp-bounces@mailman.ccsds.org</a>> on behalf of Matthew Cosby <<a href="mailto:Matt.Cosby@Goonhilly.org">Matt.Cosby@Goonhilly.org</a>><br>
<b>Date: </b>Monday, October 26, 2020 at 9:27 AM<br>
<b>To: </b>"<a href="mailto:sls-slp@mailman.ccsds.org">sls-slp@mailman.ccsds.org</a>" <<a href="mailto:sls-slp@mailman.ccsds.org">sls-slp@mailman.ccsds.org</a>><br>
<b>Subject: </b>[EXTERNAL] [Sls-slp] Updated Book</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<p class="MsoNormal">All,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Here is the updated book from the working group today.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Regards, Matt.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><b><span style="mso-fareast-language:EN-GB">Matthew Cosby</span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="mso-fareast-language:EN-GB">Chief Technology Officer
</span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="mso-fareast-language:EN-GB">Goonhilly Earth Station Ltd</span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="mso-fareast-language:EN-GB"><img border="0" width="801" height="87" style="width:8.3437in;height:.9062in" id="Picture_x0020_7" src="cid:image001.jpg@01D6AD21.F65722C0"></span></b><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
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