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<p class="MsoNormal"><span style="color:#1F497D;mso-fareast-language:EN-US">Hi, Cheol. On point (1), I think the current text is better, as it is simpler and more general: we really want to say that the value of the checksum is zero if it cannot be calculated,
no matter where the calculation is attempted (i.e., either at the sending end, for insertion into the EOF PDU, or at the receiving end for validation of the checksum in the EOF PDU).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D;mso-fareast-language:EN-US">On point (2), the reason to use 0 to indicate ¡°modular checksum¡± is to sustain backward compatibility with the original CFDP specification. We want implementations of the old and new
specifications to be able to interoperate without error, and the CFDPv1 revisions have so far been designed to achieve that. If the new checksum type field occupies space that was defined as ¡°reserved, all zeros¡± in the original spec then a cfdpv1 entity
receiving data from a cfdpv0 entity will use the correct checksum algorithm provided we define checksum ID zero to mean ¡°modular checksum¡±.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D;mso-fareast-language:EN-US">Scott<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> <span lang="KO" style="font-family:"Gulim",serif">
±¸Ã¶È¸</span> <chkoo@kari.re.kr> <br>
<b>Sent:</b> Sunday, May 26, 2019 6:43 PM<br>
<b>To:</b> sis-cfdpv1@mailman.ccsds.org; Burleigh, Scott C (312B) <scott.c.burleigh@jpl.nasa.gov><br>
<b>Subject:</b> [EXTERNAL] RE: updated CFDP Revisions draft<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">Hi Scott,<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">Thank you for the changes. Please find my comments as follows;<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">1) Section 4.1.2<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">Is it more clear when target PDU format is specified? i.e.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">When an entity is required to perform checksum calculation of a given type but is for any reason unable to do so, the value of the checksum shall
be zero.</span><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">to<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">When an entity is required to perform checksum calculation of a given type but is for any reason unable to do so, the value of the
<span style="color:red">file </span>checksum <span style="color:red">in the EOF PDU</span> shall be zero.<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:12.0pt;font-family:"Times New Roman",serif"><o:p> </o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">Or I would think it is helpful if receiving entity is able to know that the file checksum in the EOF PDU to be received will
be zero because in that case receiving entity don<span lang="KO">¡¯</span>t have to calculate checksum incrementally, which I believe some agencies perform it for time saving because it could be an issue when big file is transferred. So would it make sense?<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:12.0pt;font-family:"Times New Roman",serif"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">When an entity is required to perform checksum calculation of a given type but is for any reason unable to do so, the value of the checksum shall
be zero.</span><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">to<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">When an entity is required to perform checksum calculation of a given type but is for any reason unable to do so,
<span style="color:red">the checksum type in the Metadata PDU and the value of the file checksum in the EOF PDU shall be zero.</span></span><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">If so, the default checksum type for modular checksum should be
<span lang="KO">¡®</span>1<span lang="KO">¡¯</span> or so.<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">2) Section 5.2.5<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">I think that 6 for the length of checksum type is too long and some space could be requested for future use. In my opinion,
for interoperable operation an applicable checksum algorithm should be selectable among 2 or 3, which each agency should implement as minimum and mandatory.<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">FYI, for example checksum type could be 3 bit for length and value are as follows;<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"> - 0 (no checksum type or checksum operation is not applicable at current transaction) ; I think at the last CCSDS meetings,
we discussed the checksum type of zero (0) would be no checksum, 1 for modular checksum, 2 for CRC32 and so on.<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"> - 1 (CFDP mandatory checksum type #1)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:10.0pt;word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">- 2 (CFDP mandatory checksum type #2)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:10.0pt;word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">- 3 (CFDP mandatory checksum type #3)<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:10.0pt;word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">- 4 ~ 7 (CFDP user defined checksum type #1 ~ #4)<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">Best,<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D">Cheol<o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="word-break:break-all"><span style="font-size:10.0pt;font-family:"Malgun Gothic",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> SIS-CFDPV1 <<a href="mailto:sis-cfdpv1-bounces@mailman.ccsds.org">sis-cfdpv1-bounces@mailman.ccsds.org</a>>
<b>On Behalf Of </b>Burleigh, Scott C (312B) via SIS-CFDPV1<br>
<b>Sent:</b> Saturday, May 25, 2019 5:17 AM<br>
<b>To:</b> <a href="mailto:sis-cfdpv1@mailman.ccsds.org">sis-cfdpv1@mailman.ccsds.org</a><br>
<b>Cc:</b> <a href="mailto:osvaldo.peinado@dlr.de">osvaldo.peinado@dlr.de</a>; <a href="mailto:madalier@antarateknik.com">
madalier@antarateknik.com</a>; <a href="mailto:jens.janssen@dlr.de">jens.janssen@dlr.de</a>; Thomas Gannett <<a href="mailto:thomas.gannett@tgannett.net">thomas.gannett@tgannett.net</a>>;
<a href="mailto:Jeremy.Mayer@dlr.de">Jeremy.Mayer@dlr.de</a>; Cola, Tomaso (<a href="mailto:Tomaso.deCola@dlr.de">Tomaso.deCola@dlr.de</a>) <<a href="mailto:Tomaso.deCola@dlr.de">Tomaso.deCola@dlr.de</a>><br>
<b>Subject:</b> [SIS-CFDPV1] updated CFDP Revisions draft<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi, all. I have made all the changes to the revised CFDP Blue Book that I think are needed in order to make the file checksum algorithm selectable by reference to the new SANA checksum algorithm registry. The updated document is now in
CWE at <a href="https://cwe.ccsds.org/sis/docs/SIS-CFDPV1/Draft%20Documents/727x0b5%20--%20Specification%20--%20Blue%20Book/727x0p42_working%202.doc?Web=1">
https://cwe.ccsds.org/sis/docs/SIS-CFDPV1/Draft%20Documents/727x0b5%20--%20Specification%20--%20Blue%20Book/727x0p42_working%202.doc?Web=1</a>. Please take a look at it when you have a moment; I¡¯d like to send a final draft to Tom and ask for a supplementary
Agency review soon, maybe as early as next month.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Scott<o:p></o:p></p>
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