[Sls-slp] USLP_MC_OCF ambiguities
john.pietras at gst.com
Thu May 20 23:35:35 UTC 2021
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 220.127.116.11 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 18.104.22.168 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.".
2) Paragraph 22.214.171.124 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:
a) 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
b) 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)?]
As currently stated, bullet (a) seems to be either a redundant subset of 126.96.36.199 or somehow inconsistent with 188.8.131.52 (but I can't figure out which it is. If (according to 184.108.40.206) 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, 220.127.116.11 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).
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 18.104.22.168.
Thanks for any clarification that you can provide.
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