<span style=" font-size:10pt;font-family:sans-serif">Hi Tomaso,</span>
<br>
<br><span style=" font-size:10pt;font-family:sans-serif">maybe I am just
confused but I have some difficulties to understand what this text actually
means (in particular, what is meant by all outstanding CP segments?).
It also seems dependent on the sender's strategy when to send CPs.</span>
<br>
<br><span style=" font-size:10pt;font-family:sans-serif">Actually, looking
at 6.13 I am wondering whether we need this at all. 6.13 allows to cancel
a session with RLEXC if the number of transmission problems exceeds an
established limit. Maybe this could also cover re-transmission cycle limits?</span>
<br>
<br><span style=" font-size:10pt;font-family:sans-serif">Thinking about
this, I believe we need to leave some room for implementation-specific
limits which could come in a lot of different flavours (absolute re-transmitted
amount of data, relative re-transmitted amount of data, number of queued
segments for re-transmission, ....). It just seems strange that for one
of these 'implementation-specific' limits we have a specific error code
(RXMTCYCEXC).</span>
<br>
<br><span style=" font-size:10pt;font-family:sans-serif">Regards,</span>
<br><span style=" font-size:10pt;font-family:sans-serif">Felix</span>
<br>
<br>
<br>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">From:
</span><span style=" font-size:9pt;font-family:sans-serif"><Tomaso.deCola@dlr.de></span>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">To:
</span><span style=" font-size:9pt;font-family:sans-serif"><kscott@mitre.org>,
<sis-dtn@mailman.ccsds.org>, <Felix.Flentge@esa.int></span>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">Date:
</span><span style=" font-size:9pt;font-family:sans-serif">25/02/2021
14:17</span>
<br><span style=" font-size:9pt;color:#5f5f5f;font-family:sans-serif">Subject:
</span><span style=" font-size:9pt;font-family:sans-serif">RE:
Telecon Notes 20210224</span>
<br>
<hr noshade>
<br>
<br>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">Hi
All,</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri">Concerning
the point on the retransmission cycle limit, this is first appearing on
RFC 5326 at the end of section 6.2.2 (beginning of page 34) and copied
here below for your convenience:</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">There
may be other implementation-specific limits that may cause an</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
LTP implementation to initiate session-cancellation procedures. One</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
such limit is the maximum number of retransmission-cycles seen. A</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
retransmission cycle at the LTP Sender comprises the two related</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
events: the transmission of all outstanding CP segments from the</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
sender, and the reception of all RS segments issued from the receiver</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
in response to those CP segments. A similar definition would
apply</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
at the LTP Receiver but relate to the reception of the CP segments</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
and transmission of all RS segments in response. Note that
the</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
retransmitted CP and RS segments remain part of their original</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
retransmission-cycle. Also, a single CP segment may cause multiple</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
RS segments to be generated if a reception report would not fit in
a</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
single data link-MTU-sized RS segment; all RS segments that are part</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
of a reception report belong to the same retransmission cycle to</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
which the CP segment belongs. In the presence of severe channel</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
error conditions, many retransmission cycles may elapse before red-</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
part transmission is deemed successful; an implementation may</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
therefore impose a retransmission-cycle limit to shield itself from
a</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
resource-crunch situation. If an LTP sender notices the</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
retransmission-cycle limit being exceeded, it SHOULD initiate the</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
Cancel Session procedure (</span><a href="https://tools.ietf.org/html/rfc5326#section-6.19"><span style=" font-size:10pt;color:#0082bf;font-family:Courier New"><u>Section
6.19</u></span></a><span style=" font-size:10pt;font-family:Courier New">),
queuing a CS segment with</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
reason-code RXMTCYCEXC and sending a transmission-session</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New">
cancellation notice (</span><a href="https://tools.ietf.org/html/rfc5326#section-7.5"><span style=" font-size:10pt;color:#0082bf;font-family:Courier New"><u>Section
7.5</u></span></a><span style=" font-size:10pt;font-family:Courier New">)
to the client service.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:10pt;font-family:Courier New"> </span></p>
<br><a href=mailto:Felix.Flentge@esa.int><span style=" font-size:10pt;color:#0082bf;font-family:Courier New">@Felix.Flentge@esa.int</span></a><span style=" font-size:10pt;font-family:Courier New">:
which aspects did you want to make normative?</span>
<br><span style=" font-size:11pt;font-family:Calibri">Best Regards,</span>
<br><span style=" font-size:11pt;font-family:Calibri"> </span>
<br><span style=" font-size:11pt;font-family:Calibri">Tomaso</span>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:12pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:11pt;font-family:Calibri"><b>From:</b>
SIS-DTN <sis-dtn-bounces@mailman.ccsds.org> <b>On Behalf Of </b>Dr.
Keith L Scott<b><br>
Sent:</b> Mittwoch, 24. Februar 2021 17:52<b><br>
To:</b> sis-dtn@mailman.ccsds.org<b><br>
Subject:</b> [Sis-dtn] Telecon Notes 20210224</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:12pt;font-family:Calibri"> </span></p>
<p style="margin-top:240pt;margin-Bottom:75pt"><span style=" font-size:9pt"><b>SIS-DTN
Telecon</b></span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt"> </span></p>
<p style="margin-top:240pt;margin-Bottom:75pt"><span style=" font-size:9pt"><b>LTP</b></span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">Took
some notes in the SharePoint List here:</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><a href=https://cwe.ccsds.org/fm/wiki/Lists/SISDTN%20LTP%20Update%202021/AllItems.aspx><span style=" font-size:9pt;color:#0082bf"><u>https://cwe.ccsds.org/fm/wiki/Lists/SISDTN%20LTP%20Update%202021/AllItems.aspx</u></span></a><span style=" font-size:9pt">
</span></p>
<p style="margin-top:240pt;margin-Bottom:75pt"><span style=" font-size:9pt"><b>What
testing / experimentation to drive out issues?</b></span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">•
LTP Extension Header vs. small Green Blocks to signal adaptive coding and
modulation.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">•
ESA looking to use LTP for optical; no experimentation expected for 8-12
months</span></p>
<p style="margin-top:240pt;margin-Bottom:75pt"><span style=" font-size:9pt"><b>ReTx
cycle limit & Discretionary Checkpoints</b></span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">People
to come up with draft clarifying language and we’ll review. Consult
the RFC5326 text to see if we want to ‘normativeize’ it. Keith
to collect text from RFC5326 to provide context.</span></p>
<p style="margin-top:240pt;margin-Bottom:75pt"><span style=" font-size:9pt"><b>BPv7</b></span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">Keith
to build a list of items like the LTP list for discussion at next meeting.</span></p>
<p style="margin-top:240pt;margin-Bottom:75pt"><span style=" font-size:9pt"><b>BPSec</b></span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">In
Security WG processing; we need to notify them of status of BPSec doc in
IETF.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">People
need to review current draft and we’ll work any proposed changes to the
SEA-SEC WG ASAP:</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><a href="https://tools.ietf.org/html/draft-ietf-dtn-bpsec-27"><span style=" font-size:9pt;color:#0082bf"><u>https://tools.ietf.org/html/draft-ietf-dtn-bpsec-27</u></span></a><span style=" font-size:9pt">
</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">Default
security context from IETF is probably not what we want in CCSDS; we might
need to define our own set.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">ESA
to start an activity on security.</span></p>
<p style="margin-top:240pt;margin-Bottom:75pt"><span style=" font-size:9pt"><b>NM
Books</b></span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">Links
to I-Ds</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">NM
books going through IETF, about to become WG documents, changes as a result
of reviews may be coming over the next 8-12 months.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:9pt">ICPA
Need Dates for NM updated to <b>2028</b>, we can prioritize the other
efforts above these.</span></p>
<p style="margin-top:0px;margin-Bottom:0px"><span style=" font-size:14pt;font-family:Calibri"> </span></p>
<p style="margin-top:0px;margin-Bottom:0px"></p>
<p style="margin-top:0px;margin-Bottom:0px"></p>