[Sls-slp] CCSDS IPoC and USLP Updates

[Kazz, Greg (US 312B)]

Dear SLP WG (Keith and Tomaso too),

I took the liberty of adding the USLP space data link protocol to the IP over CCSDS blue book, since it was missing this key space data link protocol (SDLP).
Please see the update I produced in our SLP WG CWE directory under the following URL:

https://cwe.ccsds.org/sls/docs/Forms/AllItems.aspx?RootFolder=%2Fsls%2Fdocs%2FSLS%2DSLP%2FMeeting%20Materials%2F2022%2FFall%2FIPoC&View=%7BAE8FB44C%2DE80A%2D42CF%2D8558%2DFB495ABB675F%7D&&InitialTabId=Ribbon%2ERead&VisibilityContext=WSSTabPersistence

Upon updating IPoC, I noticed that USLP was missing the Virtual Channel Packet (VCP) and Virtual Channel Access Service (VCA). For IPoC, it seemed odd that all the other SDLPs had VCP, but USLP didn’t.
I think the rationale for not including it was essentially, USLP has both MAP Packet Service and MAP Access Service, and if a user didn’t plan on really using MAP IDs and preferred to use the GVCID as the SAP, then one would simply set the MAP ID to default value 0, and be done. However, that is not consistent with Telecommand (TC) in that it has provision for both MAP Packet and VC Packet, and as documented in IPoC, a user could use either service to interface with IPoC. Therefore, I think the short cut we may in USLP doesn’t help and I truly believe there will be users that want VCP or VCA service and don’t plan on using any MAPs at all. So I am requesting both SLS WG and SIS Area folks to take a look at this updated IPoC document. It will be a topic for discussion at the SLP WG meeting at the Fall 2022 meeting. SLP WG will coordinate final changes with SIS area.

The other document for the SLP WG folks to review and comment on is USLP blue book. I added the VCP service and VCA service to the document. This involves mostly adding the service parameters and primitives which are well known and documented in Telecommand (TC) with only a few changes due to the document references for the COP-1 and SDLS Core Protocol. The last change I added has to do with relaxing the USLP constraint of only limiting the “Maximum number of transfer frames given to the C&S Sublayer as a Single Data Unit” from 1 to Integer. Rationale is that NASA/JPL has the SRL (Surface Retrieval Lander) plans on using multiple TC frames within a CLTU. So in weaker signal environments, missions like SRL plan on packing as many TC frames into a CLTU as possible, to minimize the overhead (maximize the efficiency) in the number of uplink bits they transmit. In addition, since TC also allows for one or more TC frames to be contained within a CLTU, there is no advantage to be different in this respect with TC. I recall that the SLP WG was trying to see if any space agency would place more than one frame within a CLTU, and now we do have that use case, so we need to respond to it and ease up on that constraint, which quite frankly is too imposing and doesn’t provide us any advantage to be so rigid.

So the sections in the USLP Blue book impacted are:
Section 3, Annex A (PICS Proforma) – adding VCP and VCA services
Section 2.4.1, 4.2.10.7 (All frames generation), 4.3.10.1.6 (All Frames Reception), Note in 4.3.10.2, Table 5-1 Managed Parameter, Annex A PICs Proforma for the value of that Managed Parameter (from one to Integer)

The USLP Blue Book updates are under the following URL:

https://cwe.ccsds.org/sls/docs/Forms/AllItems.aspx?RootFolder=%2Fsls%2Fdocs%2FSLS%2DSLP%2FMeeting%20Materials%2F2022%2FFall%2FUSLP%20Blue%20Book&FolderCTID=0x012000439B56FF51847E41B5728F9730D7B55F&View=%7BAE8FB44C%2DE80A%2D42CF%2D8558%2DFB495ABB675F%7D

See file with August 1 in the file name.

All of these updates are done in the Word Revision Feature so they show up in RED underlined text.
These updates will also be discussed at the Fall 2022 SLP WG meeting. Your review and comments are essential and most welcome.

Best regards,

Greg
Chair SLP WG

Greg Kazz
Principal Engineer
Technical Group Supervisor,
312B Project Protection, Project Software, and End to End Information System Engineering
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

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