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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hello all,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Ed Greenberg has hit on the most important practical aspect of
making this decision. Mission designers expect CCSDS protocols to provide reliable
delivery of their spacecraft commands from the ground system to the on-board ‘command
and data-handling’ system (currently, via the COP-1 protocol). Please,
in our effort to make commanding more secure, let’s make sure that we
still provide the existing capabilities.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Best regards,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Tim<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
sls-slp-bounces@mailman.ccsds.org [mailto:sls-slp-bounces@mailman.ccsds.org] <b>On
Behalf Of </b>Moury Gilles<br>
<b>Sent:</b> Friday, October 16, 2009 10:43 AM<br>
<b>To:</b> Greenberg, Edward (JPL-313B)[Caltech-JPL]; Howie Weiss; Matt Cosby<br>
<b>Cc:</b> Shames, Peter M. (JPL-3130)[Caltech-JPL]; SLS-SLP WG<br>
<b>Subject:</b> RE : [Sls-slp] Security, NGU and New TC services and there
effecton COP-1<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>Good afternoon Ed and Matt,</span><o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>At our next SDLS WG meeting, we will have to decide where we insert
the Data Link Security sublayer within the CCSDS Data Link Layer. Several
options exist. If I understood well, what you agree on is that we can, for TC
at the receiving end :</span><o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>- either perform security check before the FARM, in that case any
AD frame rejected by security will be NACKed and retransmitted by COP</span><o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>- either perform security check after FARM, just before handling TC
segment to the upper layer. In that case, upper layers will have to handle
missing segments/packets (I assume DLS protocol will not include yet
another retransmission protocol !).</span><o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>In short, your common conclusion is that there is no
interaction between DLS protocol and COP-1 protocol which ever the order in
which we process them. Am I correct ?</span><o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>Personally, I favour "security check before FARM"
scenario since, as Ed states, it provides automatic retransmission of frames
which did not pass security checks.</span><o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>Best regards,</span><o:p></o:p></p>
</div>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>Gilles</span><o:p></o:p></p>
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<p><span lang=FR style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Gilles
MOURY</span> <br>
<span lang=FR style='font-size:10.0pt;font-family:"Arial","sans-serif"'>CNES
Toulouse</span><span lang=FR> </span><o:p></o:p></p>
<blockquote style='margin-top:5.0pt;margin-right:0in;margin-bottom:5.0pt'>
<p class=MsoNormal style='margin-bottom:12.0pt'><span lang=FR style='font-size:
10.0pt;font-family:"Tahoma","sans-serif"'>-----Message d'origine-----<br>
<b>De :</b> sls-slp-bounces@mailman.ccsds.org
[mailto:sls-slp-bounces@mailman.ccsds.org] <b>De la part de</b> Greenberg,
Edward (313B)<br>
<b>Envoyé :</b> jeudi 15 octobre 2009 18:23<br>
<b>À :</b> Howie Weiss; Matt Cosby<br>
<b>Cc :</b> Shames, Peter M (3130); SLS-SLP WG<br>
<b>Objet :</b> Re: [Sls-slp] Security, NGU and New TC services and there
effecton COP-1</span><span lang=FR><o:p></o:p></span></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif"'>As usual Howie you are correct....except
there needs to be a process somewhere for the system on an end to end basis to
report the failure at the security point or at the application layer. Are
we going to invent a protocol to do that at the security layer;. notifying the
remote user of the failure at the security check point? Cop-1 will
respond to the loss of a frame and request a replacement. I guess we
could relate you argument to TCP; its role is to handle link problems (ordering
and loss) and security (using IPSec) is riding on top of that. If the
system requires in order delivery of good data without loss then there needs to
be a protocol at the application layer that requests the missed item. I
don’t believe that we want to do that.....so I’ll continue to say
that the COP is there to assure the delivery of in order without loss delivery.<br>
<br>
<br>
On 10/15/09 7:51 AM, "Howie Weiss" <<a
href="Howard.Weiss@cobham.com">Howard.Weiss@cobham.com</a>> wrote:</span><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:10.0pt;
font-family:"Calibri","sans-serif"'>Where we disagree</span> <span
style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>is that the COP
isn't "broken" if you put the security afterwards and the security
layer fails its checks.</span> <span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>This
comes back to where the COP/FARM has finished its job (to guarantee</span> <span
style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>delivery of
complete in</span> <span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>sequence,
error free commands). Our disagreement was that I believe that the COP has
finished when it hands the command to the next process (whatever that is)</span>
<span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>– in
this</span> <span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>example
it is the security layer.</span> <span style='font-size:10.0pt;font-family:
"Calibri","sans-serif"'>You believe that the COP</span> <span style='font-size:
10.0pt;font-family:"Calibri","sans-serif"'>has not</span> <span
style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>completing its job
correctly if the next process or processes throws the</span> <span
style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>command</span> <span
style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>away for another
failure</span> <span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>–
in this case</span> <span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>if
the security has failed.<br>
</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><br>
This is analogous to IPSec being above the link and network (IP) layers.
While IP does not guarantee in-order delivery it does (sort of) guarantee
that the packet isn't clobbered (based on its weak checksum). But IP is
supposed to simply hand-of what it thinks is a good packet to IPSec for
security processing. IP washes its (virtual) hands of the packet and it becomes
IPSec's responsibility to pass it up to the next layer as "good" to
to send it to the bit-bucket because it didn't pass muster.<br>
<br>
Howie<br>
<br>
</span><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>-----------------------<br>
</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><br>
</span><b><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'>Howard
Weiss <br>
</span></b><span style='font-size:8.0pt;font-family:"Calibri","sans-serif"'>Technical
Director<br>
SPARTA National Security Sector<br>
Cobham Analytic Solutions<br>
T: 443 430 8089<br>
F: 443 430 8238<br>
C: 410 261 1479<br>
<a href="howard.weiss@cobham.com">howard.weiss@cobham.com</a><br>
</span><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'><br>
</span><span style='font-size:8.0pt;font-family:"Calibri","sans-serif"'>SPARTA,
Inc., dba Cobham Analytic Solutions, 7110 Samuel Morse Dr., Columbia MD 21046
www.sparta.com <<a href="http://www.sparta.com/">http://www.sparta.com/</a>>
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