[Sls-slp] [EXTERNAL] USLP_MC_OCF ambiguities

Mon May 24 16:00:39 UTC 2021

Hi John,
I appreciate your logic John. I consider your additional points post-RIDs that make sense to handle now.
Below in red are my responses.
I’ve updated the draft USLP blue book to accommodate the following changes in between **…** in red below.
That draft book, with the date, May 23 in the file name  is on the SLP CWE at:
https://cwe.ccsds.org/sls/docs/Forms/AllItems.aspx?RootFolder=%2Fsls%2Fdocs%2FSLS%2DSLP%2FMeeting%20Materials%2F2021%2FSpring%2FRIDs%2FUSLP%20RIDs&FolderCTID=0x012000439B56FF51847E41B5728F9730D7B55F&View=%7BAE8FB44C%2DE80A%2D42CF%2D8558%2DFB495ABB675F%7D
I encourage the SLP WG, to review my recommendations below and inform me if you have a difference of opinion by May 31, 2021.
Please also see the details regarding these changes below.
Thanks much,
Greg

From: SLS-SLP <sls-slp-bounces at mailman.ccsds.org> on behalf of John Pietras <john.pietras at gst.com>
Date: Thursday, May 20, 2021 at 4:35 PM
To: "sls-slp at mailman.ccsds.org" <sls-slp at mailman.ccsds.org>
Cc: "matteo.renesto at telespazio.de" <matteo.renesto at telespazio.de>, "Holger.Dreihahn at esa.int" <Holger.Dreihahn at esa.int>, Wolfgang Hell <wo_._he at t-online.de>
Subject: [EXTERNAL] [Sls-slp] USLP_MC_OCF ambiguities

Members of the SDLP WG,
I realize that it is past the time for submitting USLP RIDs, but there are a few requirements that are confusingly stated (to me, at least), and I’d like to get the correct interpretation of their intent. If you agree with my interpretations, then perhaps the requirements can also be “disambiguated” as part of the update of the Blue Book.

  1.  Paragraph 4.1.5.3 states “If for at least one VC within the MC, the VC managed parameter ‘Inclusion of OCF Required’ is ‘True’, then an OCF shall be included in every USLP Frame of that MC.”

This implies that if every frame of all VCs  on the MC is required to carry an OCF when ‘Inclusion of OCF Required’ is ‘True’ for any *one* VC, then ‘Inclusion of OCF Required’ must equal ‘True’ for *every* VC on the MC. In other words, ‘Inclusion of OCF Required’ is really a property of the MC, not one (or all) of its VCs. Note that there is no qualification here as to whether the MC and/or VCs carry fixed or variable length frames. If that’s the correct interpretation, then it would seem to make sense to make ‘Inclusion of OCF Required’ a managed parameter of the MC, not each VC, in which case 4.1.5.3 could be restated
“If MC managed parameter ‘Inclusion of OCF Required’ is ‘True’, then an OCF shall be included in every USLP Frame of that MC.”.
That is the correct interpretation, ‘Inclusion of OCF Required’ is really a property of the MC. When we formulated the requirement, I don’t think this generalization occurred to us. It makes 4.1.5.3 more succinct.

Now 4.1.5.3 reads:  **“If MC managed parameter ‘Inclusion of OCF Required’ is ‘True’, then an OCF shall be included in every USLP Frame of that MC.” **

** That also affected additional changes to 1) add MC managed parameter, ‘Inclusion of OCF Required’ to table 5-2 and remove it from table 5-3; Fixed the note 2 in 4.2.8.2; Fixed the overview in 3.6.1; Fixed the PICS Proforma USLP 116 to say MC in table 2. **

  1.  Paragraph 4.1.5.4 states “If the managed parameter ‘MC Transfer Frame Type’ is ‘Variable Length’ for the subordinate VCs included in that MC, then the following rule applies:

  1.  for fixed-length VC frames, if the associated VC Managed Parameter, ‘Inclusion of OCF Required’ is set to ‘True’, the OCF shall be included in every USLP Frame; and
  2.  for variable-length VC frames, if the associated VC Managed Parameter, ‘Inclusion of OCF Allowed’ is set to ‘True’, the OCF shall be included as desired based upon mission rules.”

[Aside – should VC Managed Parameter” be VC managed parameter” in bullets (a) and (b)?] We will let Tom Gannett make it all consistent and I will double check it.

As currently stated, bullet (a) seems to be either a redundant subset of 4.1.5.3 or somehow inconsistent with 4.1.5.3 (but I can’t figure out which it is. If (according to 4.1.5.3) every frame of every VC of the MC must contain OCFs when ‘Inclusion of OCF Required’ is set to ‘True’ for *any* VC regardless of the frames are fixed or variable length, then it is unnecessary to restate the same requirement for the fixed length frames on a so-called variable length VC. In that case, 4.1.5.4 could be simplified to
“If the managed parameter ‘VC Transfer Frame Type’ is ‘Variable Length’ and the associated VC managed parameter, ‘Inclusion of OCF Allowed’ is set to ‘True’, the OCF shall be included as desired based upon mission rules.”
(it’s not necessary to state the dependency on the MC being variable-length since the VC can be VL only if the MC is VL). Yes, this is the case.

However, if bullet (a) might be saying that in the case where the variable-length frames are present, only the frames on that VC are required  to carry OCFs but not the other VCs on the MC, then that contradicts 4.1.5.3. This is not the case.

                Bullet a) is redundant.

So Now the new 4.1.5.4 is simplified and reads:  ** “If the managed parameter ‘VC Transfer Frame Type’ is ‘Variable Length’ and the associated VC managed parameter, ‘Inclusion of OCF Allowed’ is set to ‘True’, then the OCF shall be included as desired based upon mission rules.” **

Thanks for any clarification that you can provide.

Best regards,

John

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