[Sls-slp] AOS 5-year review: typo and VCF Service issues

Tue Oct 27 23:06:03 UTC 2020

Gian Paolo,
I was trying to make minimal changes to the existing (new) text, but I agree with you that trying to squeeze multiple thoughts into a single sentence is problematic.

My main concern was to eliminate any misinterpretation that there could be only one VCF or MCF service instance per space link – I’m particularly sensitive to this point, having just completed the Forward Frame CSTS book, the main point of which is to allow multiple external (with respect to the ground station) sources of VC frames to share the same space link, where each FF-CSTS instance has its own dedicated VC and therefore maps into a separate instance of the VCF service.

I think that your wording is an improvement on my proposal. In any case, I would be happy with any wording that makes clear that there can possibly be:
- one or more instances of the VCF service (each with its own GVCID);
- one or more instances of MCF Service (each with its own MCID, where multiple MCs on the same space link are valid);
- one or more VCs (each with its own GVCID) generated by the service provider itself; and/or
- one or more MCs (each with its own MCID) generated by the service provider itself

[NOTE – I believe that MCs that are populated by frames received through instances of the VC Frame service should be considered to be MCs created by the provider system, since those frames come into the MC through the service provider’s VC Mux function]

Best regards,
John

From: SLS-SLP [mailto:sls-slp-bounces at mailman.ccsds.org] On Behalf Of Gian.Paolo.Calzolari at esa.int
Sent: Tuesday, October 27, 2020 6:31 PM
To: Kazz, Greg J(US 312B) <greg.j.kazz at jpl.nasa.gov>
Cc: Kazz, Greg J (US 312B) via SLS-SLP <sls-slp at mailman.ccsds.org>
Subject: [Sls-slp] AOS 5-year review: typo and VCF Service issues

Dear All,
        the typo remark as presented in John's e-mail looks correct (but I did not check the documents).

For the other remark I am getting more doubts.
The current sentence is not looking correct to me, but I am not sure the proposed correction is the best one.

As specified in 2.2.4 RESTRICTIONS ON SERVICES bullet c: If the Virtual Channel Frame Service exists on a Virtual Channel, other services shall not exist simultaneously on that Virtual Channel.
Let's consider the original sentence:  “The Virtual Channel Frame Service transfers the independently created AOS Transfer Frames through a space link, possibly together with AOS Transfer Frames identified by other GVCID values created by the service provider itself.”
If we split it, I read something like this

 “The Virtual Channel Frame Service transfers the independently created AOS Transfer Frames through a space link.

 The Virtual Channel Frame Service transfers possibly also AOS Transfer Frames identified by other GVCID values created by the service provider itself.”

In other words it looks as the other frames are also transferred by the VCF Service while they are transferred by other services (or service instances) on other VCs/MCs.
The same issue rises also with the rewording proposed by John.

A possible improvement could then be something like this:

“Each Virtual Channel Frame Service instance transfers the independently created AOS Transfer Frames through a space link.

Those AOS Transfer Frames are possibly multiplexed on the space link together with other AOS Transfer Frames identified by different GVCID/MCID values.

These other AOS Transfer Frames can have been created by other VCF/MCF Service instances and/or by the service provider itself.”

I understand this is likely not to be the best formulation, but may be a good starting point for a less ambiguous formulation.

I also guess that a similar improvement should apply to 2.2.3.7 for the sentence "The Master Channel Frame Service transfers the independently created AOS Transfer Frames through the space link, together with AOS Transfer Frames created by the service provider itself." noting that <If the Master Channel Frame Service exists on a Master Channel, other services shall not exist simultaneously on that Master Channel.>.

Best regards

Gian Paolo

From:        "Kazz, Greg J\(US 312B\) via SLS-SLP" <sls-slp at mailman.ccsds.org<mailto:sls-slp at mailman.ccsds.org>>
To:        "Kazz, Greg J (US 312B) via SLS-SLP" <sls-slp at mailman.ccsds.org<mailto:sls-slp at mailman.ccsds.org>>
Date:        27-10-20 22:53
Subject:        [Sls-slp] FW: [EXTERNAL] RE: Updated TM & AOS 5-year review files from SLP WG meeting Oct 27
Sent by:        "SLS-SLP" <sls-slp-bounces at mailman.ccsds.org<mailto:sls-slp-bounces at mailman.ccsds.org>>
________________________________

Dear SLP WG members,

John Pietras has what I believe are some good points below.

Please let me know your opinion of his proposed changes below

Thanks!
Greg

Chair SLP WG

From: John Pietras <john.pietras at gst.com<mailto:john.pietras at gst.com>>
Date: Tuesday, October 27, 2020 at 2:23 PM
To: "Kazz, Greg J (US 312B)" <greg.j.kazz at jpl.nasa.gov<mailto:greg.j.kazz at jpl.nasa.gov>>
Subject: [EXTERNAL] RE: Updated TM & AOS 5-year review files from SLP WG meeting Oct 27

Dear Greg and all,

I’ve taken a quick look at the updates TM and AOS books and I found a typo and a statement that I think is misleading.

First the typo – As modified, the first sentence of the second paragraph under 2.2.3.6 of the AOS book now reads “For a given service instance, only one user, identified with the GVCID of the Virtual Channel, and each VCF Service instance on a physical channel must utilize a unique GVCID value.” The phrase “can use this service on a Virtual Channel” has been erroneously deleted.

The sentence should read “For a given service instance, only one user, identified with the GVCID of the Virtual Channel, can use this service on a Virtual Channel, and each VCF Service instance on a physical channel must utilize a unique GVCID value.”

What I believe to be a misleading statement appears in two forms in both the AOS and TM books. The first sentence of the third paragraph under 2.2.3.6 of the AOS book now reads “The Virtual Channel Frame Service transfers the independently created AOS Transfer Frames through a space link, possibly together with AOS Transfer Frames identified by other GVCID values created by the service provider itself.”

My interpretation of this sentence is that there can be only one instance of the VCF Service per space link, with the implication that all other VCs on the space link are generated “by the service provider itself”.

I believe that a more accurate, less ambiguous statement is

“Each Virtual Channel Frame Service instance transfers the independently created AOS Transfer Frames through a space link, possibly together with AOS Transfer Frames identified by other GVCID values created by users of other VCF Service instances, users of Master Channel Frame service instances (see 2.2.3.7), and/or by the service provider itself.”

If my suggestion is accepted, the same change should be applied to 2.2.3.6 of the TM book.

The analogous situation applies to the MCF Service. The equivalent modification would be to change first sentence of the third paragraph under 2.2.3.7 of the AOS book (and 2.2.9 of the TM book) to read “Each Master Channel Frame Service instance transfers the independently created AOS Transfer Frames through the space link, possibly together with AOS Transfer Frames identified by other MCID values created by users of other MCF Service instances or by the service provider itself.“

Best regards,

John

From: SLS-SLP [mailto:sls-slp-bounces at mailman.ccsds.org] On Behalf Of Kazz, Greg J (US 312B) via SLS-SLP
Sent: Tuesday, October 27, 2020 12:43 PM
To: Kazz, Greg J (US 312B) via SLS-SLP <sls-slp at mailman.ccsds.org<mailto:sls-slp at mailman.ccsds.org>>
Subject: [Sls-slp] Updated TM & AOS 5-year review files from SLP WG meeting Oct 27

Dear SLP WG,

Attached please find two files as a result of the 5-year review:

1.        Updated 132.0-B TM SDLP book modified during our SLP WG meeting today on Oct 27.

2.        Updated 732.0-B AOS SDLP book modified during our SLP WG meeting today on Oct 27.

When I have a chance, I will load both of them to the SLP WG CWE directory under the Fall 2020 meeting.

Best regards,

Greg Kazz

Principal Engineer

Technical Group Supervisor,

PSSE/EEISE/PPSE (312B)

Jet Propulsion Laboratory

4800 Oak Grove Dr., M/S 301-490

Pasadena, CA 91109

1+(818)393 6529(voice)

1+(818)393 6871(fax)

email: greg.j.kazz at jpl.nasa.gov<mailto:greg.j.kazz at jpl.nasa.gov>

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