<div dir="ltr"><div>If you want to implement such a hack for your mission, by all means do it. Ensure that the endpoints you're interested in know the secret handshake (and that the use of such doesn't violate any rules of the specs) and have at it. At that point it's a purely mission/implementation-specific modification, which is fine. Doing an Orange book to document a 'temporary' solution using timestamp sequence numbers seems like overkill, especially if the consensus is that there are better ways to achieve the same goals.</div><div><br></div><div>Others could weigh in here, but I suspect the chances that the IETF would support adding the creation timestamp sequence number method to the BPv7 spec are pretty low, so we'd bifurcate from the yet-to-be-realized numerous terrestrial BP implementations, whereas a specified and registered extension block, while it might not be picked up by every implementation, would at least have grounding in the BPv7 framework.</div><div><br></div><div>--------</div><div><br></div><div>* There's a bigger issue here, in that nowhere in 9171 nor the CCSDS spec does it say that the timestamp OR any specific extension block (metadata) MUST be provided to the receiving application agent. So to use either method we're going to need an implementation that understands the streaming sequence mechanism makes that information available (to the application, to network management via an implementation-specific ADM or other interface?). Such an implementation would (could) be entirely spec-compliant, but the capability isn't guaranteed by the specs.</div><div><br></div><div>The extension block method also suffers from the risk that some joker might encrypt it so that any processing would have to be done post-decryption (presumably at the destination node itself). At least the timestamp sequence number is guaranteed to be in the clear.</div><div><br></div><div><br></div><div>9171 definition of 'Delivery' (my emphasis):</div><div>A bundle is considered to have been delivered at a node subject to a registration as soon as the ADU that is the <font color="#0000ff">payload of the bundle</font>, together with any relevant metadata (<i><font color="#0000ff">an implementation matter</font></i>), has been presented to the node's application agent in a manner consistent with the state of that registration.</div><div><br></div><div>CCSDS BPv7 spec (my emphasis):</div><div>4.3.7 BUNDLE DELIVERY INDICATION PARAMETERS<br>4.3.7.1 The delivery indication parameters shall be the ADU and the metadata from 4.3.7.2 below pertaining to the ADU.<br>4.3.7.2 The value of the delivery indications parameters shall include the following:<br>a) application data unit is an administrative record;<br>b) acknowledgement by application is requested.<br><br></div><div>NOTE – Implementations <font color="#0000ff">may also include other information</font> with the Bundle Delivery Indication Parameters such as the source EID, creation time, and/or information from extension blocks.<br></div><div><br></div><div><br></div><div><br></div><div> --keith</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Aug 10, 2023 at 3:38 AM Sanchez Net, Marc (US 332H) <<a href="mailto:marc.sanchez.net@jpl.nasa.gov">marc.sanchez.net@jpl.nasa.gov</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-857705750228435222">
<div lang="EN-US" style="overflow-wrap: break-word;">
<div class="m_-857705750228435222WordSection1">
<p class="MsoNormal">All,<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">I would suggest we consider Felix’s and Jonathan’s proposal in the context of an CCSDS orange book (maybe green or yellow?), as it does address a critical issue (that of bundle accountability) to operationalize DTN in flight projects. I
do agree that the best way to implement this functionality is with an extension block. However, in the near-term, and from an infusion standpoint, having a “poor man’s way” of getting the job done is valuable (e.g., new extension block means more dev time,
more requirements, more V&V, more mission cost, etc.), as long as we understand and document its limitations.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">From a technical standpoint:<u></u><u></u></p>
<ul style="margin-top:0in" type="disc">
<li class="m_-857705750228435222MsoListParagraph" style="margin-left:0in">I am not too convinced by the use of the BPCF as currently proposed. There seems to be side effects (e.g., “<b><span lang="EN-GB">In case 10 with different destination endpoint IDs,
the BPA has to guarantee that the same values can only appear with different bundle creation times”</span></b><span lang="EN-GB">) and RFC9171 states that “Bundle processing control flags that are unrecognized be ignored”, so we risk having DTN nodes with
different behavior?<u></u><u></u></span></li><li class="m_-857705750228435222MsoListParagraph" style="margin-left:0in">I am more in favor of documenting that by not resetting the sequence number, which is explicitly allowed in RF9171 and (as Josh points out) still serves the original purpose of the
sequence number, projects may identify gaps and perform data accountability. Since this is method is a “poor man’s way” of achieving this in the near-term, management by policy (internal to the project, or by SLA agreement with the network provider) seems
ok. <u></u><u></u></li><li class="m_-857705750228435222MsoListParagraph" style="margin-left:0in">I am not too convinced that timestamps and sequence numbers are the best way of doing in-order delivery. The difference between in-order delivery and gap identification is that the
former requires modifying how a DTN node delivers bundles to the application (maybe forwarding is affected too?), so it seems a change in bundle processing behavior. On the other hand, the latter is just a change to the reporting mechanism, which seems less
intrusive. For example, a DTN node could implement an indication to flag a gap (as detected by the sequence number), which then triggers flight SW to generate an EVR destined for the MOC (which may flow as a payload to another bundle or go via a non-DTN channel).
It seems to me that such behavior would not need to be interoperable (after all, EVRs aren’t).<u></u><u></u></li></ul>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Thanks,<u></u><u></u></p>
<div>
<p class="MsoNormal">-----------------------------------------------------------------------------------------------------------------------<u></u><u></u></p>
<p class="MsoNormal">Marc Sanchez Net (332H)<u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:10pt;color:gray">Telecommunications Engineer</span><u></u><u></u></p>
<p class="MsoNormal" style="background:white"><span style="font-size:10pt;color:gray">Jet Propulsion Laboratory<u></u><u></u></span></p>
<p class="MsoNormal" style="background:white"><span style="font-size:10pt;color:gray">Cell:</span><span style="font-size:10pt;font-family:Arial,sans-serif;color:rgb(34,34,34)"> </span><span style="font-size:10pt;font-family:Arial,sans-serif;color:black"><a href="mailto:(617)%20953-7977" target="_blank"><span style="color:rgb(5,99,193)">(617)
953-7977</span></a></span><span style="font-size:10pt;font-family:Arial,sans-serif;color:rgb(0,112,192)">
</span><span style="font-size:10pt;color:gray">|</span><span style="font-size:10pt;font-family:Arial,sans-serif;color:rgb(0,112,192)">
</span><span style="font-size:10pt;color:gray">Email:</span><span style="font-size:10pt;font-family:Arial,sans-serif;color:rgb(34,34,34)"> </span><span style="color:black"><a href="mailto:marc.sanchez.net@jpl.nasa.gov" target="_blank"><span style="font-size:10pt;font-family:Arial,sans-serif">marc.sanchez.net@jpl.nasa.gov</span></a></span><span style="font-size:9.5pt;font-family:Arial,sans-serif;color:rgb(34,34,34)"><u></u><u></u></span></p>
<p class="MsoNormal">-----------------------------------------------------------------------------------------------------------------------<u></u><u></u></p>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="MsoNormal"><b>From:</b> SIS-DTN <<a href="mailto:sis-dtn-bounces@mailman.ccsds.org" target="_blank">sis-dtn-bounces@mailman.ccsds.org</a>> <b>
On Behalf Of </b>sburleig.sb--- via SIS-DTN<br>
<b>Sent:</b> Wednesday, August 9, 2023 2:42 PM<br>
<b>To:</b> 'Keith Scott' <<a href="mailto:keithlscott@gmail.com" target="_blank">keithlscott@gmail.com</a>>; 'Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC]' <<a href="mailto:jonathan.j.wilmot@nasa.gov" target="_blank">jonathan.j.wilmot@nasa.gov</a>><br>
<b>Cc:</b> 'Dr. Keith L Scott via SIS-DTN' <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>>; 'Birrane, Edward J. (GSFC-460.0)[Johns Hopkins University Applied Physics Lab]' <<a href="mailto:edward.j.birrane@nasa.gov" target="_blank">edward.j.birrane@nasa.gov</a>>; 'Singh, Somendra {Simon} (GSFC-5820)' <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>>; 'Carlo Caini'
<<a href="mailto:carlo.caini@unibo.it" target="_blank">carlo.caini@unibo.it</a>><br>
<b>Subject:</b> Re: [Sis-dtn] [EXTERNAL] R: Special use of sequence number in bundle creation time stamp<u></u><u></u></p>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">I really think that’s best; simpler, more powerful, much easier to standardize.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Scott<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="MsoNormal"><b>From:</b> Keith Scott <<a href="mailto:keithlscott@gmail.com" target="_blank">keithlscott@gmail.com</a>>
<br>
<b>Sent:</b> Wednesday, August 9, 2023 2:17 PM<br>
<b>To:</b> Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC] <<a href="mailto:jonathan.j.wilmot@nasa.gov" target="_blank">jonathan.j.wilmot@nasa.gov</a>><br>
<b>Cc:</b> Gao, Jay L (JPL-332C)[JPL Employee] <<a href="mailto:jay.l.gao@jpl.nasa.gov" target="_blank">jay.l.gao@jpl.nasa.gov</a>>;
<a href="mailto:sburleig.sb@gmail.com" target="_blank">sburleig.sb@gmail.com</a>; Carlo Caini <<a href="mailto:carlo.caini@unibo.it" target="_blank">carlo.caini@unibo.it</a>>; Felix Flentge <<a href="mailto:Felix.Flentge@esa.int" target="_blank">Felix.Flentge@esa.int</a>>; Dr. Keith L Scott via SIS-DTN <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>>;
Singh, Somendra {Simon} (GSFC-5820) <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>>; Birrane, Edward J. (GSFC-460.0)[Johns Hopkins University Applied Physics Lab] <<a href="mailto:edward.j.birrane@nasa.gov" target="_blank">edward.j.birrane@nasa.gov</a>><br>
<b>Subject:</b> Re: [Sis-dtn] [EXTERNAL] R: Special use of sequence number in bundle creation time stamp<u></u><u></u></p>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<p class="MsoNormal">I'm all for the capability, but an extension block seems the way to go. I think either SIS-DTN, or even SOIS, could do this (and/or in conjunction with the IETF), and get the extension block registered with IANA for all to use. In the
meantime, it seems like it's something that's only used at the endpoints, so you could just use one of the private block types until the block is registered, then switch to the allocated type number.<u></u><u></u></p>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"> --keith<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div>
<p class="MsoNormal">On Wed, Aug 9, 2023 at 10:19 PM Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC] via SIS-DTN <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>> wrote:<u></u><u></u></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin:5pt 0in 5pt 4.8pt">
<div>
<div>
<div>
<p class="MsoNormal">All,<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"> The primary purpose of the proposed Source timestamp sequence number is to indicate if DTN lost anything between the source and destination. Not being able to tell a user of
your network if you dropped any of their data is an issue with many in the science community. What they put in the bundle or how they sequence it is not a DTN problem.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">We are trying to infuse DTN into a very conservative community. We should include mechanisms to determine where things may have gone wrong.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">Kind regards,<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"> Jonathan Wilmot<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">CCSDS SOIS Area Director<u></u><u></u></p>
<p class="MsoNormal">GSFC DTN Systems Engineer<u></u><u></u></p>
<p class="MsoNormal">cFS Architecture<u></u><u></u></p>
<p class="MsoNormal">Cell 301-751-2658<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">
<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<div>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="MsoNormal"><b>From:</b> Gao, Jay L (US 332C) <<a href="mailto:jay.l.gao@jpl.nasa.gov" target="_blank">jay.l.gao@jpl.nasa.gov</a>>
<br>
<b>Sent:</b> Wednesday, August 9, 2023 3:49 PM<br>
<b>To:</b> <a href="mailto:sburleig.sb@gmail.com" target="_blank">sburleig.sb@gmail.com</a>; 'Carlo Caini' <<a href="mailto:carlo.caini@unibo.it" target="_blank">carlo.caini@unibo.it</a>>; 'Felix Flentge' <<a href="mailto:Felix.Flentge@esa.int" target="_blank">Felix.Flentge@esa.int</a>>;
'Dr. Keith L Scott via SIS-DTN' <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>>; Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC] <<a href="mailto:jonathan.j.wilmot@nasa.gov" target="_blank">jonathan.j.wilmot@nasa.gov</a>><br>
<b>Cc:</b> Birrane, Edward J. (GSFC-460.0)[Johns Hopkins University Applied Physics Lab] <<a href="mailto:edward.j.birrane@nasa.gov" target="_blank">edward.j.birrane@nasa.gov</a>>; Singh, Somendra {Simon} (GSFC-5820) <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>><br>
<b>Subject:</b> Re: [Sis-dtn] [EXTERNAL] R: Special use of sequence number in bundle creation time stamp<u></u><u></u></p>
</div>
</div>
<p class="MsoNormal"> <u></u><u></u></p>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black">All,</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black"> </span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black">The proposed use of the sequence number seems to suggest it is design only for a kind of application that simply streams data.</span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black"> </span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black">If you have an application that runs on top of BP that implements any kind of interactive messages as well as data. Then the sequence
number is no longer a valid gap detector because not all bundles carries in-order data payload. </span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black"> </span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black">I am not sure we try to standardize a new use of the sequence numbers to fit only a specific type of application that could be supported
over BP.</span><u></u><u></u></p>
</div>
<div>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black"> </span><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12pt;color:black">Jay</span><u></u><u></u></p>
</div>
<div id="m_-857705750228435222m_4091429703776898859Signature">
<div>
<div>
<div>
<div>
<p class="MsoNormal"><span style="font-size:10pt;font-family:Tahoma,sans-serif">
<br>
<br>
Jay L. Gao<br>
_____________________________________________<br>
Communications and Architecture Research Section<br>
Jet Propulsion Laboratory<br>
4800 Oak Grove Drive<br>
M/S: 238-343<br>
Pasadena, CA 91109<br>
<a href="mailto:Jay.L.Gao@jpl.nasa.gov" target="_blank">Jay.L.Gao@jpl.nasa.gov</a><br>
TEL: 818-354-9528</span><u></u><u></u></p>
</div>
</div>
</div>
</div>
</div>
</div>
<div class="MsoNormal" align="center" style="text-align:center">
<hr size="2" width="98%" align="center">
</div>
<div id="m_-857705750228435222m_4091429703776898859divRplyFwdMsg">
<p class="MsoNormal"><b><span style="color:black">From:</span></b><span style="color:black"> SIS-DTN <<a href="mailto:sis-dtn-bounces@mailman.ccsds.org" target="_blank">sis-dtn-bounces@mailman.ccsds.org</a>>
on behalf of Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC] via SIS-DTN <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>><br>
<b>Sent:</b> Wednesday, August 9, 2023 10:16 AM<br>
<b>To:</b> <a href="mailto:sburleig.sb@gmail.com" target="_blank">sburleig.sb@gmail.com</a> <<a href="mailto:sburleig.sb@gmail.com" target="_blank">sburleig.sb@gmail.com</a>>; 'Carlo Caini' <<a href="mailto:carlo.caini@unibo.it" target="_blank">carlo.caini@unibo.it</a>>;
'Felix Flentge' <<a href="mailto:Felix.Flentge@esa.int" target="_blank">Felix.Flentge@esa.int</a>>; 'Dr. Keith L Scott via SIS-DTN' <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>><br>
<b>Cc:</b> Birrane, Edward J. (GSFC-460.0)[Johns Hopkins University Applied Physics Lab] <<a href="mailto:edward.j.birrane@nasa.gov" target="_blank">edward.j.birrane@nasa.gov</a>>; Singh, Somendra {Simon} (GSFC-5820) <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>><br>
<b>Subject:</b> Re: [Sis-dtn] [EXTERNAL] R: Special use of sequence number in bundle creation time stamp</span>
<u></u><u></u></p>
<div>
<p class="MsoNormal"> <u></u><u></u></p>
</div>
</div>
<div>
<div>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Scott,<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> There seems to be some pros and cons in play that we have not documented well. I will create some material for a future DTN WG (week or two) to discuss and include the security aspects as Vint commented.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Just want to ensure we all are on the same page, and we base a forward path on documented analysis.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Kind regards,<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> Jonathan Wilmot<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">CCSDS SOIS Area Director<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">GSFC DTN Systems Engineer<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">cFS Architecture<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Cell 301-751-2658<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<div>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="m_-857705750228435222m4091429703776898859xmsonormal"><b>From:</b> <a href="mailto:sburleig.sb@gmail.com" target="_blank">
sburleig.sb@gmail.com</a> <<a href="mailto:sburleig.sb@gmail.com" target="_blank">sburleig.sb@gmail.com</a>>
<br>
<b>Sent:</b> Wednesday, August 9, 2023 12:53 PM<br>
<b>To:</b> Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC] <<a href="mailto:jonathan.j.wilmot@nasa.gov" target="_blank">jonathan.j.wilmot@nasa.gov</a>>; 'Carlo Caini' <<a href="mailto:carlo.caini@unibo.it" target="_blank">carlo.caini@unibo.it</a>>; 'Felix
Flentge' <<a href="mailto:Felix.Flentge@esa.int" target="_blank">Felix.Flentge@esa.int</a>>; 'Dr. Keith L Scott via SIS-DTN' <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>><br>
<b>Cc:</b> Singh, Somendra {Simon} (GSFC-5820) <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>>; Birrane, Edward J. (GSFC-460.0)[Johns Hopkins University Applied Physics Lab] <<a href="mailto:edward.j.birrane@nasa.gov" target="_blank">edward.j.birrane@nasa.gov</a>><br>
<b>Subject:</b> RE: [EXTERNAL] R: [Sis-dtn] Special use of sequence number in bundle creation time stamp<u></u><u></u></p>
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<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
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<div>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Jonathan, it sounds to me like the core issue here is whether to add all of this bundle labeling and sequence checking functionality to the existing requirements on primary block processing or to instead define it rigorously
in an extension block and leave primary block processing alone.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">If the additional processing requirements are imposed on primary block processing, then all deployments of all implementations of BPv7 are affected, including those for whom none of this functionality is needed in any
way. They will of course not recognize the new bundle processing control flags and will ignore them, but bundle uniqueness will routinely be lost unaccountably if (for example) bundle creation time is zero and bundle sequence numbers roll over at 2^16 per
sequence number length flag values 01.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">It may be possible to constrain the required supplementary BPv7 specification in a way that shields existing BPv7 users from its impact. But I believe that will be a difficult specification to write and the cost of
getting it wrong will be significant.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">I think it would be a much better use of SCaN’s DTN resources to draft a clean extension block specification. At the data rates being contemplated here, I think the small increment in bundle size should be an acceptable
price to pay for these capabilities.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Scott<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<div>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="m_-857705750228435222m4091429703776898859xmsonormal"><b>From:</b> Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC] <<a href="mailto:jonathan.j.wilmot@nasa.gov" target="_blank">jonathan.j.wilmot@nasa.gov</a>>
<br>
<b>Sent:</b> Wednesday, August 9, 2023 9:20 AM<br>
<b>To:</b> Carlo Caini <<a href="mailto:carlo.caini@unibo.it" target="_blank">carlo.caini@unibo.it</a>>; 'Felix Flentge' <<a href="mailto:Felix.Flentge@esa.int" target="_blank">Felix.Flentge@esa.int</a>>; 'Dr. Keith L Scott via SIS-DTN' <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>>;
<a href="mailto:sburleig.sb@gmail.com" target="_blank">sburleig.sb@gmail.com</a><br>
<b>Cc:</b> Singh, Somendra {Simon} (GSFC-5820) <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>>; Birrane, Edward J. (GSFC-460.0)[Johns Hopkins University Applied Physics Lab] <<a href="mailto:edward.j.birrane@nasa.gov" target="_blank">edward.j.birrane@nasa.gov</a>><br>
<b>Subject:</b> RE: [EXTERNAL] R: [Sis-dtn] Special use of sequence number in bundle creation time stamp<u></u><u></u></p>
</div>
</div>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Carlo,<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> For the use cases that we are considering, any time a source node sends the same bundle to two or more destinations it uses Scott’s proposed multi-destination protocol. If a node wants to send different bundles
to different destinations, then they are different services. (org.node.service) In our flight system data model source “.service” is a discriminator for different bundle types/ADU. NASA.PACE.QuickLookScience is one service and NASA.PACE.BulkData is another.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">I can see an issue with the set of common “service” numbers, but maybe those are in the destination EID not the source.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">I agree we don’t want to break the original use case.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Kind regards,<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> Jonathan Wilmot<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">CCSDS SOIS Area Director<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">GSFC DTN Systems Engineer<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">cFS Architecture<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal">Cell 301-751-2658<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
<div>
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<p class="m_-857705750228435222m4091429703776898859xmsonormal"><b>From:</b> Carlo Caini <<a href="mailto:carlo.caini@unibo.it" target="_blank">carlo.caini@unibo.it</a>>
<br>
<b>Sent:</b> Wednesday, August 9, 2023 11:50 AM<br>
<b>To:</b> 'Felix Flentge' <<a href="mailto:Felix.Flentge@esa.int" target="_blank">Felix.Flentge@esa.int</a>>; 'Dr. Keith L Scott via SIS-DTN' <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>>;
<a href="mailto:sburleig.sb@gmail.com" target="_blank">sburleig.sb@gmail.com</a><br>
<b>Cc:</b> Singh, Somendra {Simon} (GSFC-5820) <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>>; Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC] <<a href="mailto:jonathan.j.wilmot@nasa.gov" target="_blank">jonathan.j.wilmot@nasa.gov</a>><br>
<b>Subject:</b> [EXTERNAL] R: [Sis-dtn] Special use of sequence number in bundle creation time stamp<u></u><u></u></p>
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<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
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<b><span style="font-size:10pt;color:black">CAUTION:</span></b><span style="color:black">
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<p class="m_-857705750228435222m4091429703776898859xmsonormal"><span style="font-size:12pt;color:black">I fully agree with Scott on his comments and suggestions. More generally, I would avoid, whenever possible, the use of a parameter designed to a specific end, such as timestamp
sequence number here, to different purposes. However, appealing it may be on a short term, it is looking for troubles on the long term.</span><u></u><u></u></p>
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<div>
<p class="m_-857705750228435222m4091429703776898859xmsonormal"><span style="font-size:12pt;color:black">Specifically, the timestamp sequence number is not the same as an hupothetical bundle sequence number, as pointed out by Scott. Moreover, if we assume that a source generates
bundles to a give destination to specific rate, e.g. one bundle per second, the sequence number increment between two consecutive bundles of this flow may be larger than one. For example, the first sequence number of the bundle flow could be 1 and the second
5. It is enough that the same source generates in the meantime other 3 bundles to different destinations.
</span><u></u><u></u></p>
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<p class="m_-857705750228435222m4091429703776898859xmsonormal"><span style="font-size:12pt;color:black">Yours,</span><u></u><u></u></p>
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<p class="m_-857705750228435222m4091429703776898859xmsonormal"><span style="font-size:12pt;color:black"> Carlo</span><u></u><u></u></p>
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<p class="m_-857705750228435222m4091429703776898859xmsonormal"><span style="font-size:12pt;color:black"> </span><u></u><u></u></p>
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<div id="m_-857705750228435222m_4091429703776898859x_divRplyFwdMsg">
<p class="m_-857705750228435222m4091429703776898859xmsonormal"><b><span style="color:black">Da:</span></b><span style="color:black"> SIS-DTN <<a href="mailto:sis-dtn-bounces@mailman.ccsds.org" target="_blank">sis-dtn-bounces@mailman.ccsds.org</a>> per conto di sburleig.sb--- via
SIS-DTN <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>><br>
<b>Inviato:</b> mercoledì 9 agosto 2023 17:31<br>
<b>A:</b> 'Felix Flentge' <<a href="mailto:Felix.Flentge@esa.int" target="_blank">Felix.Flentge@esa.int</a>>; 'Dr. Keith L Scott via SIS-DTN' <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>><br>
<b>Cc:</b> 'Singh, Somendra {Simon} (GSFC-5820)' <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>>; 'Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC]' <<a href="mailto:jonathan.j.wilmot@nasa.gov" target="_blank">jonathan.j.wilmot@nasa.gov</a>><br>
<b>Oggetto:</b> Re: [Sis-dtn] Special use of sequence number in bundle creation time stamp</span>
<u></u><u></u></p>
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<p class="m_-857705750228435222m4091429703776898859xmsonormal"> <u></u><u></u></p>
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<p class="m_-857705750228435222m4091429703776898859xxmsonormal">Hi, Felix. One thing to keep in mind is that the purpose of the sequence number in the bundle creation timestamp is to distinguish among bundles that have the same bundle creation time. This can occur when bundles
are created at a very high rate or when bundle creation time is zero due to the absence of an accurate clock.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal">I would suggest that using bundle creation timestamp sequence numbers for other purposes makes it more difficult to use those numbers for their original purpose.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal">If sequence numbering of bundles in these various ways is important, I think it would be better to encode those numbers (and the flags describing their significance) in an immutable extension block, i.e., an extension
block that is one of the additional targets of a block integrity block covering the primary block.<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal">Scott<u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"> <u></u><u></u></p>
<div>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><b>From:</b> SIS-DTN <<a href="mailto:sis-dtn-bounces@mailman.ccsds.org" target="_blank">sis-dtn-bounces@mailman.ccsds.org</a>>
<b>On Behalf Of </b>Felix Flentge via SIS-DTN<br>
<b>Sent:</b> Wednesday, August 9, 2023 7:43 AM<br>
<b>To:</b> Dr. Keith L Scott via SIS-DTN <<a href="mailto:sis-dtn@mailman.ccsds.org" target="_blank">sis-dtn@mailman.ccsds.org</a>><br>
<b>Cc:</b> Singh, Somendra {Simon} (GSFC-5820) <<a href="mailto:simon.singh@nasa.gov" target="_blank">simon.singh@nasa.gov</a>>; Wilmot, Jonathan J. (GSFC-580.0)[VANTAGE SYSTEMS INC] <<a href="mailto:jonathan.j.wilmot@nasa.gov" target="_blank">jonathan.j.wilmot@nasa.gov</a>><br>
<b>Subject:</b> [Sis-dtn] Special use of sequence number in bundle creation time stamp<u></u><u></u></p>
</div>
</div>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"> <u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">Dear All,</span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">I think we have had some initial exchange on the use of the sequence number in the bundle creation timestamp some time ago. Meanwhile, we had a number of side meetings with Jonathan, Simon and others
to further discuss the topic of ‘flows’, compressed bundle reporting and network management.</span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">We have arrived at a point where we think that it makes sense to allow using the sequence number in the primary header for identifying gaps in sequences of bundles or to even allow for in-sequence
delivery.</span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">The basic idea is that the sequence number does not get reset to zero but is incrementing by one until a specified maximum. Further we might use different, individual sequence numbers per source
node ID or per destination endpoint ID. Such a behaviour might be governed by policy or even indicated in the Primary Block’s Processing Control Flags, like</span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<ol start="1" type="1">
<li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">Use two bits to specify whether the creation timestamp sequence number is used in special way:</span><u></u><u></u></li></ol>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<ul type="disc">
<li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">00 – single sequence number - no specific usage</span><u></u><u></u></li><li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">01 – an individual sequence number is used per source node id</span><u></u><u></u></li><li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">10 – an individual sequence number is used per destination endpoint id</span><u></u><u></u></li><li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">11 – reserved (until we find a good usage; maybe individual sequence number per next hop)</span><u></u><u></u></li></ul>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><b><span lang="EN-GB">In case 10 with different destination endpoint IDs, the BPA has to guarantee that the same values can only appear with different bundle creation times!</span></b><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<ol start="2" type="1">
<li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">Use of two bits to indicate the maximum length of the sequence number (00 above) or individual sequence numbers (01 and 10 above):</span><u></u><u></u></li></ol>
<ul type="disc">
<li class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">00 - sequence numbers are assigned somehow (reset to zero, randomly, ..)</span><u></u><u></u></li><li class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">01 - increasing sequence number up to 2^16-1</span><u></u><u></u></li><li class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">10 - increasing sequence number up to 2^32-1</span><u></u><u></u></li><li class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">11 - increasing sequence number up to 2^64-1</span><u></u><u></u></li></ul>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">My main questions:</span><u></u><u></u></p>
<ol start="1" type="1">
<li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">Does it make sense to use flags in the primary header for this purpose or is it sufficient to document that sequence numbers can be used in that way and leave it up to policy to specify certain behaviours? I have a slight preference for using
the BPCF as it seems more formal and could ease interoperability (and the sequence number is in the primary header, so why not indicate it there).</span><u></u><u></u></li><li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">If we want to use BPCF, what is the way to specify this? Should we / do we need to go IETF or could CCSDS be sufficient (to start with)? Ideally we would use some of the reserved first 16 bits (e.g. Bit 7 – 10)</span><u></u><u></u></li><li class="m_-857705750228435222m4091429703776898859xxmsolistparagraph">
<span lang="EN-GB">No matter whether we want to use BCPF or not, I think something should end up in the CCSDS BB as soon as possible. So, maybe there is a chance for a late RID (if it does not delay the overall publication process). We should start discussing
(maybe tomorrow).</span><u></u><u></u></li></ol>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">Regards,</span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB">Felix</span><u></u><u></u></p>
<p class="m_-857705750228435222m4091429703776898859xxmsonormal"><span lang="EN-GB"> </span><u></u><u></u></p>
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