[Css-csts] elimination of the Monitored Data Collection FR

[Barkley, Erik J (US 3970)]

Dear John,

I concur with your assessment.  I think we need to consider that the CSS Area recommendations are essentially interface specs and not implementation specs.  To that end, although an implementation needs to gather its monitor data somehow, the key standardization aspect is the transfer of that monitor data (as in the Cross Support Transfer Service or CSTS).  By contrast, stating what I'll call "slippery-slope" roll-up rules that includes such possibilities as "status is 'interrupted', with the understanding that some/most services are still being provided" is just asking for trouble.  If there is to be a report on each service being provided as to its status I think that makes sense.  But in terms of aggregational assessment think it is much better to defer this to the agency (should they decide that this provides value).   In the end I think eliminating collection FR is well within keeping of the Einstein maximum of  "Everything should be made as simple as possible, but no simpler."

Best regards,
-Erik

From: CSS-CSTS <css-csts-bounces at mailman.ccsds.org> On Behalf Of John Pietras
Sent: Tuesday, January 21, 2020 13:30
To: Wolfgang Hell <wo_._he at t-online.de>; Holger.Dreihahn at esa.int
Cc: CCSDS_CSTSWG (css-csts at mailman.ccsds.org) <css-csts at mailman.ccsds.org>
Subject: [EXTERNAL] [Css-csts] elimination of the Monitored Data Collection FR

Dear Wolfgang and Holger,
For several years we have questioned the need for the Monitored Data Collection functional resource, which I had put into the FR Reference Model as a placeholder. I finally concluded that there is indeed no need for this FR and have eliminated it from both the FR Ref Model draft Magenta Book and the set of "Tier 1" FRM definitions that I provided at the end of December and updated earlier this month.

However, in eliminating that FR I overlooked one side-effect: sections 9.2 and 9.3 of the Monitored Data CSTS Blue Book refine the definitions of production status and production status change to be specified in terms of the status of the MD Collection function. If someone were to try to implement the MD CSTS BB as written, the referenced source for production status would not exist. [Note that the MD-CSTS does not have a production configuration change event because any changes are reported directly through MD-CSTS's monitoring of those resources - see the Note under 9.1 of the MD CSTS Blue Book.]

The focus on the MD Collection function as the source of production status stemmed from the fact that the MD service nominally reports on all resources in the service package of which the MD service instance is a part. Since different resources of the service package may not all be necessarily operational continuously throughout the whole execution of the service package (for example, one instance of SLE RCF may be only enabled for a sub-period of a long (e.g., deep space) contact, it would not be appropriate to ascertain 'configured' vs 'operational' production based on some all-or-nothing criteria. Similarly, if multiple data flows are being supported during the execution of the service package and one of those flows are interrupted while all others are operating as planned, should the overall production status be deemed 'interrupted' or continue to be 'operational' since at least one flow was performing properly? It was for reasons such as these that MD-CSTS production status was deemed to be equal to the resource status of the MD Collection function.

Something needs to be done regarding the definition of the MD-CSTS production status. Perhaps the simplest approach is to defer to the Provider CSSS the interpretation of what constitutes the aggregate status of all resources used in the service package. In reality, this is what already happens for SLE production status - some Providers actually instrument their systems and assess overall production status based on those readings, while other Providers treat production status as and ESLT operator input. Under this approach, for example, Agency A could rule that if *any* services are operating properly then production status is 'operational' even though some resources are only 'configured' and others might even be 'interrupted'; Agency B might take the opposite approach, where any interruption results in 'interrupted' production status even though the great majority of the services are still being provided; and Agency C develops some metrics that determine what percentage of scheduled services need to be interrupted before the production status goes from 'operational' to 'interrupted' [Note - this last may seem like an exaggerated use case, but in fact in the early days of the NASA Space Network, when TDRSS was still a leased service from a private company, the payments for service provided were calculated using such percentage-based metrics]. If we were to adopt this approach sections 9.2 and 9.3 of the MD-CSTS would be replaced by "requirements" that the Provider document the method(s) by which the 4 production status values are determined for MD-CSTS.

On the other hand, if we feel uncomfortable leaving, we could make an attempt at defining our recommended metrics for determining the production status values, e.g.:

  *   if all resources are configured and they are only supposed to be configured at the time, then prod status is 'configured'
  *   if all resources that are supposed to be operational are operational and all resources that are supposed to be configured are configured, then prod status is 'operational'
  *   if one or more resources are interrupted, then prod status is 'interrupted', with the understanding that some/most services are still being provided
  *   if one or more resources are halted, the prod status is 'halted', with the understanding that some/most services are still being provided

While we could do this, I think that it is simpler to just defer the decision on the metrics to the Provider CSSS.

In any case, the references to the MD Collection function need to be removed from the MD CSTS book. Whatever decision we arrive at, it could be done by Technical Corrigendum.

Best regards,
John
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