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<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">All,</span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">In an earlier email in this thread, Greg commented that he understood that many missions multiplex different “packet channels” into the same VC, but that he did not see this happening
in an interoperable way. I think that Greg has hit on the important factor here – what is exposed in an interoperable, cross-supported way?</span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Back when we wrote the original AOS book, we had the notion that “cross support” users would be able to access individual packet channels via standard intefaces. This notion was
formalized in the Cross Support Reference Model, Part 1 – Space Link Extension Services Blue Book (colloquially known as the “SLE Ref Model”), which envisioned two “flavors” of Forward Space Packet (TC and AOS) and one Return Space Packet service. Those services
would have allowed multiple FSP instances to carry packete channels all destined for the same VC.<o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">As it turned out, only the TC flavor of the Forward Space Packet service was ever realized. Different instances of the (TC) FSP service are indeed capable of carrying different
packet channels destined for the same VC. The FSP service uses MAP, so the necessary packet channel multiplexing into VCs is accomplished (indirectly) through MAP Multiplexing.
</span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">But had the AOS FSP been realized, it *<b>would</b>* have required the packet channel muxing that currently resides in the SPP. But since it wasn’t realized, the main use case
(that I know of) disappears, and perhaps packet channel multiplexing is indeed no longer needed at a cross-support interoperability level, which I agree with Greg is the important factor in considering whether to retain the specification in the SPP (or migrate
it back into one or more of the SDLP books). </span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Best regards,</span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">John</span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="color:black"><o:p></o:p></span></p>
<p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><span style="color:black"><o:p></o:p></span></p>
<p><b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"> Gian.Paolo.Calzolari@esa.int [mailto:Gian.Paolo.Calzolari@esa.int]
<br>
<b>Sent:</b> Tuesday, January 30, 2018 8:55 AM<br>
<b>To:</b> Kazz, Greg J (312B)<br>
<b>Cc:</b> John Pietras; sls-slp@mailman.ccsds.org; SLS-SLP<br>
<b>Subject:</b> Re: [Sls-slp] Results of Discussion with Takahiro Yamada on Revising SPP Blue Book</span><span style="color:black"><o:p></o:p></span></p>
<p><span style="color:black"> <o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Greg,</span><span style="color:black">
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black"> what we have to be sure it captured in our CCSDS books is the following situation (e.g. for a TM/AOS link)</span><span style="color:black">
<o:p></o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">There multiple sources generating packet contents and asking creation of packets</span>
<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Those packets are created with different APIDs depending on the source</span>
<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">Those different APIDs shall be multiplexed to produce a single packet stream:</span>
<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1"><span style="font-size:10.0pt;font-family:"Arial",sans-serif">This single packet stream is then injected in in a VC</span>
<o:p></o:p></li><li class="MsoNormal" style="color:black;mso-list:l0 level1 lfo1"> <o:p></o:p></li></ul>
<p><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">It is then correct that "The current AOS SDLP version i.e., CCSDS 732.0-B-3 Sept 2015 is agnostic about “packet channels” and “Individual CCSDS packets from multiple sources” (implying
multiple APIDs). It is really only concerned about multiplexing of packets with different PVNs onto VCs." In fact AOS would only see that single stream.</span><span style="color:black">
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">All the rest shall be done above the SDLP.</span><span style="color:black">
<br>
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">We shall check also what we lost with respect to CCSDS 103.0-B-2 (now silver) where there was a nice picture for which I attach a detail.</span><span style="color:black">
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Another document to be checked for losses is CCSDS 203.0-B-2 and even FSP that mention APID multiplexing if I remember well.</span><span style="color:black">
<br>
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Finally we shall verify all fits within the encapsulation service.</span><span style="color:black">
<br>
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Ciao</span><span style="color:black">
<br>
<br>
</span><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Gian Paolo</span><span style="color:black">
<br>
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