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<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff size=2>Good
afternoon Ed and Matt,</FONT></SPAN></DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff size=2>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
:</FONT></SPAN></DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff size=2>-
either perform security check before the FARM, in that case any AD frame
rejected by security will be NACKed and retransmitted by COP</FONT></SPAN></DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff size=2>-
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 !).</FONT></SPAN></DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff size=2>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 ?</FONT></SPAN></DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff
size=2>Personally, I favour "security check before FARM" scenario since, as Ed
states, it provides automatic retransmission of frames which did not pass
security checks.</FONT></SPAN></DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff size=2>Best
regards,</FONT></SPAN></DIV>
<DIV><SPAN class=859172714-16102009><FONT face=Arial color=#0000ff
size=2>Gilles</FONT></SPAN></DIV>
<DIV> </DIV>
<DIV> </DIV><!-- Converted from text/rtf format -->
<P><SPAN lang=fr><FONT face=Arial size=2>Gilles MOURY</FONT></SPAN> <BR><SPAN
lang=fr><FONT face=Arial size=2>CNES Toulouse</FONT></SPAN> </P>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV></DIV>
<DIV class=OutlookMessageHeader lang=fr dir=ltr align=left><FONT face=Tahoma
size=2>-----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<BR><BR></FONT></DIV><FONT
face="Calibri, Verdana, Helvetica, Arial"><SPAN style="FONT-SIZE: 11pt">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:<BR><BR></SPAN></FONT>
<BLOCKQUOTE><FONT face="Calibri, Verdana, Helvetica, Arial"><FONT
size=2><SPAN style="FONT-SIZE: 10pt">Where we
disagree</SPAN></FONT></FONT><FONT face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT size=2><FONT
face="Calibri, Verdana, Helvetica, Arial"><SPAN style="FONT-SIZE: 10pt">is
that the COP isn't "broken" if you put the security afterwards and the
security layer fails its checks.</SPAN></FONT></FONT><FONT
face="Times New Roman"><SPAN style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT
size=2><FONT face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">This comes back to where the COP/FARM has finished
its job (to guarantee</SPAN></FONT></FONT><FONT face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT size=2><FONT
face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">delivery of complete in</SPAN></FONT></FONT><FONT
face="Times New Roman"><SPAN style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT
size=2><FONT face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">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></FONT></FONT><FONT
face="Times New Roman"><SPAN style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT
size=2><FONT face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">– in this</SPAN></FONT></FONT><FONT
face="Times New Roman"><SPAN style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT
size=2><FONT face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">example it is the security
layer.</SPAN></FONT></FONT><FONT face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT size=2><FONT
face="Calibri, Verdana, Helvetica, Arial"><SPAN style="FONT-SIZE: 10pt">You
believe that the COP</SPAN></FONT></FONT><FONT face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT size=2><FONT
face="Calibri, Verdana, Helvetica, Arial"><SPAN style="FONT-SIZE: 10pt">has
not</SPAN></FONT></FONT><FONT face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT size=2><FONT
face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">completing its job correctly if the next process or
processes throws the</SPAN></FONT></FONT><FONT face="Times New Roman"><SPAN
style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT size=2><FONT
face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">command</SPAN></FONT></FONT><FONT
face="Times New Roman"><SPAN style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT
size=2><FONT face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">away for another failure</SPAN></FONT></FONT><FONT
face="Times New Roman"><SPAN style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT
size=2><FONT face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">– in this case</SPAN></FONT></FONT><FONT
face="Times New Roman"><SPAN style="FONT-SIZE: 12pt"> </SPAN></FONT><FONT
size=2><FONT face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 10pt">if the security has
failed.<BR></SPAN></FONT></FONT><FONT
face="Calibri, Verdana, Helvetica, Arial"><SPAN
style="FONT-SIZE: 11pt"><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><FONT size=2><SPAN
style="FONT-SIZE: 10pt">-----------------------<BR></SPAN></FONT><SPAN
style="FONT-SIZE: 11pt"><BR></SPAN><FONT size=2><SPAN
style="FONT-SIZE: 10pt"><B>Howard Weiss <BR></B></SPAN></FONT><FONT
size=1><SPAN style="FONT-SIZE: 8pt">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></FONT><FONT
size=2><SPAN style="FONT-SIZE: 10pt"><BR></SPAN></FONT><FONT size=1><SPAN
style="FONT-SIZE: 8pt">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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