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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;mso-fareast-language:EN-US">Hi Peter,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;mso-fareast-language:EN-US">My point was not trying to demonstrate that they are the same, but that they are similar in terms of complexity. That’s all.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">Best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">__Mario<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Shames, Peter M (US 312B) <peter.m.shames@jpl.nasa.gov>
<br>
<b>Sent:</b> 28 September 2022 20:35<br>
<b>To:</b> Mario Merri <Mario.Merri@esa.int>; CESG (cesg@mailman.ccsds.org) <cesg@mailman.ccsds.org><br>
<b>Cc:</b> Mehran Sarkarati <Mehran.Sarkarati@esa.int><br>
<b>Subject:</b> Re: [EXTERNAL] [CESG] Complexity of MO Services<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">Hi Mario,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I’m going to avoid a lengthy polemic myself.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Yes, it is true that both DTN and MAL have layered architectures. Many systems do.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">No, the MAL and the DTN BPA are not the same.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">DTN<o:p></o:p></span></p>
<ol style="margin-top:0cm" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo3"><span lang="EN-US">The DTN protocol is defined in Blue Book and it is concretely specified such that it can be directly implemented. The PDUs are concretely defined, like most CCSDS
and Internet protocols.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo3"><span lang="EN-US">A few of the CLAs are specified in this DTN BB. They are of the form “take the concrete DTN PDU and put it directly into a TCP datagram of the same length”.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo3"><span lang="EN-US">There is more than one possible CLA, because there is more than one underlying “network”, but several are defined in just a few pages of the DTN BB and the mapping
is direct from DTN PDU to CLA.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo3"><span lang="EN-US">These are idempotent.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo3"><span lang="EN-US">That’s it.
<o:p></o:p></span></li></ol>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">MAL<o:p></o:p></span></p>
<ol style="margin-top:0cm" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l3 level1 lfo6"><span lang="EN-US">The MAL is defined in abstractions in the BB (which, IMHO, is really an MB because it is abstract).<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l3 level1 lfo6"><span lang="EN-US">The MAL cannot be directly implemented from the BB, additional mappings and bindings are needed.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l3 level1 lfo6"><span lang="EN-US">The data mappings must be separately defined in a different BB before you can get to anything like a concrete PDU.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l3 level1 lfo6"><span lang="EN-US">The transport mappings must be separately defined in a different BB.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l3 level1 lfo6"><span lang="EN-US">There are many possible mappings from the abstract MAL to actual PDUs to actual transport layers. This is not one to one, it is potentially one to many.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l3 level1 lfo6"><span lang="EN-US">These mappings are not always idempotent, sometimes separate “by management”, out of band, signals are required.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l3 level1 lfo6"><span lang="EN-US">This addition of extra layers of abstraction, mappings, and no guarantee of idempotence adds complexity.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l3 level1 lfo6"><span lang="EN-US">Not really the same at all.<o:p></o:p></span></li></ol>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">As with most things in this life, you have to read the fine print. Simple abstract pictures do not do justice to reality.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Cheers, Peter<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">CESG <<a href="mailto:cesg-bounces@mailman.ccsds.org">cesg-bounces@mailman.ccsds.org</a>> on behalf of CESG <<a href="mailto:cesg@mailman.ccsds.org">cesg@mailman.ccsds.org</a>><br>
<b>Reply-To: </b>Mario Merri <<a href="mailto:Mario.Merri@esa.int">Mario.Merri@esa.int</a>><br>
<b>Date: </b>Wednesday, September 28, 2022 at 2:27 AM<br>
<b>To: </b>CESG <<a href="mailto:cesg@mailman.ccsds.org">cesg@mailman.ccsds.org</a>><br>
<b>Cc: </b>Mehran Sarkarati <<a href="mailto:Mehran.Sarkarati@esa.int">Mehran.Sarkarati@esa.int</a>><br>
<b>Subject: </b>[EXTERNAL] [CESG] Complexity of MO Services<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">Good morning,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">Today while reviewing the CCSDS Bundle Protocol Specification, my attention was caught by the following pictures in the document:<o:p></o:p></span></p>
<p class="MsoNormal"><img border="0" width="562" height="393" style="width:5.8541in;height:4.0937in" id="Picture_x0020_1" src="cid:image001.png@01D8D3F0.B6762F00"><span style="font-size:12.0pt;font-family:"Arial",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">This seems very close to the MO Framework stack, where the Technology bindings allow mapping the services to a given technology, pretty much as the Convergence Layer Adapters
in the picture above allow mapping to different network types. I would guess that in the above architecture the Bundle Protocol Agent has, at least partially, a similar role as the MAL. Clearly, the logic of devising such architectures (for both MO and BP)
is sound and allows the deployment over different technologies (networks) at the cost of some additional complexity. This complexity has to be hidden to the final users by the availability of productised SW libraries that implement the protocols/services.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">I just would like to share this analogy without any polemic. Yes, our standards are sometime complex above all if we move from the format to the services (MO, SLE, BP), but I
think that, while services are the present for communications protocols (SLE and BP), they will be the future for space applications (please note that in mainstream IT, services have been the present for quite a while, just think to the Service Oriented Architecture
(SOA) and the trend towards microservices). I think that acknowledging this and working all together to bring innovation into the space world is one of the task that CCSDS and CESG has.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">Best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">__Mario<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<o:p></o:p></p>
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