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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#467886" vlink="#96607D" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt'>FYSA. I won’t be able to join today’s telecon. I’ll try to arrange for someone to open the line, although our admin is on leave this week – apologies for my absence and for any disruption it may cause.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>Best,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>Bob<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> Robert C Durst <br><b>Sent:</b> Thursday, July 17, 2025 8:07 AM<br><b>To:</b> Birrane, Edward J. <Edward.Birrane@jhuapl.edu>; rick.taylor@ori.co<br><b>Cc:</b> tomaso.decola <tomaso.decola@dlr.de><br><b>Subject:</b> CCSDS/IETF coordination on BPv7, BPSec, and ADU fragmentation<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:11.0pt'>Ed, Rick,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>I’m writing in my capacity as CCSDS DTN Working Group chair to coordinate with you regarding operational space mission use of BPv7 and BPSec. As we’ve discussed, operational requirements will not permit the admission of unauthenticated bundles into the networks being developed for NASA or ESA missions, in particular (but certainly not limited to) LunaNet.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>As you know, this requirement, that all bundles must be authenticated by the BPSec Bundle Integrity Block, is incompatible with the BPv7 ADU fragmentation capability. Within CCSDS, we have considered a number of alternatives to address our very near-term requirement to get a profile together of BPv7 and BPSec that is consistent with mission security requirements and practical for implementation from a space mission perspective.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>The simplest approach is for us (CCSDS) to simply deprecate BPv7 ADU fragmentation with requirements such as “CCSDS implementations of BPv7 shall not produce ADU fragments.” That would avoid the issue of bundle fragments being generated and avoid the BPSec issue for bundles generated within the scope of these requirements. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>However, per RFC 9171, ADU reassembly is a BPv7 requirement, independent of ADU fragment creation, and herein lies the issue. If all bundles must be signed as a condition of network admission, and ADU fragments cannot be signed, then no fragments will be in the mission network. Flight software is a precious commodity, both in terms of onboard resource consumption and as a source of possible errors or failures. Missions will not implement ADU reassembly; the consensus within the CCSDS DTN WG is that CCSDS should not require them to. We can update the BPv7 Protocol Implementation Conformance Statement pro forma to make ADU fragmentation a “SHALL NOT” and to make ADU reassembly optional. However, at least temporarily, this places CCSDS at odds with the requirements in RFC 9171. The question from the CCSDS side is this: since both organizations concur that there is an issue, and that IETF is working to resolve the issue, does CCSDS establishing this interim profile cause a problem? And if so, does IETF have a better alternative? We look forward to collaborating with you to identify a practicable way forward.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>Thanks, and best regards,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>Bob Durst<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>Chair, CCSDS Space Internetworking Services DTN Working Group <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>Email: <a href="mailto:durst@mitre.org">durst@mitre.org</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>Cell: 703-217-7414 <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p></div></body></html>