[SIS-CFDPV1] CFDP unbounded transfers

Wed Oct 18 06:38:56 UTC 2023

Hi,

I would be very careful not to introduce additional complexity by signalling supported or unsupported features within CFDP itself. To me it does not seem to be overly useful as we don’t have ‘spontaneous’ file transactions between CFDP entities but careful mission designs with ICDs, validation, etc before we even fly. Based on my experience with flight implementations, I also doubt that such features would be implemented. I think what is much more important is to have a clear identification of the capabilities of each implementation and ways to easily communicate this. This is the idea behind the identification of optional CFDP features.

We should discuss at the meeting whether there is a need for an additional condition code (there is just one reserved left and we should not change the size). If so, I would make something more generic like ‘unsupported feature’ or ‘protocol error’.

In the long term, we would hope to run CFDP/BP and we maybe could communicate about supported features using BP network management but I would not try to build something separate for CFDP.

Regards,
Felix

From: chkoo at kari.re.kr <chkoo at kari.re.kr>
Sent: Wednesday, October 11, 2023 1:20 PM
To: Felix Flentge <Felix.Flentge at esa.int>
Cc: Wiegand, Robert E. (GSFC-5830) <robert.e.wiegand at nasa.gov>; sis-cfdpv1 at mailman.ccsds.org
Subject: RE: Re: [SIS-CFDPV1] CFDP unbounded transfers

Hi, Felix.

Add my positive vote for this. We should support such limited or constrained CFDP entity here.

We may want to add a condition code for this in Table 5-5 when the limited or constrained CFDP entity receives data which exceeds 32 bit size, such as "Big file is not supported".

If the consideration for the system that does not support partial function in the CFDP specification is necessary during the revision of CFDP specification document, I think we need some additional features for handing this functional gap between functionally different entities.

For example,

I think a function that can be used at figuring out the remote entity's functional status may be helpful, such as the supported CFDP class(class 1 only, class 1&2, class 2 only), big file supported or not, existence of CL (none, LTP only, BP only, LTP/BP, ...), remaining capacity of storage, available bandwidth, supported CFDP specification document (B4, B5, B6, ...). It is working like these, "FYI, my current CFDP supporting status have been sent. Let me have yours." We can refer the function of the Contact Header or SESS_INIT in the RFC-9174 for this query function.

Cheol
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보낸사람 : Felix Flentge via SIS-CFDPV1 <sis-cfdpv1 at mailman.ccsds.org<mailto:sis-cfdpv1 at mailman.ccsds.org>>
받는사람 : "Wiegand, Robert E. (GSFC-5830)" <robert.e.wiegand at nasa.gov<mailto:robert.e.wiegand at nasa.gov>>, "sis-cfdpv1 at mailman.ccsds.org<mailto:sis-cfdpv1 at mailman.ccsds.org>" <sis-cfdpv1 at mailman.ccsds.org<mailto:sis-cfdpv1 at mailman.ccsds.org>>
받은날짜 : 2023-10-11 (수) 16:07:38
제목 : Re: [SIS-CFDPV1] CFDP unbounded transfers
Hi Bob,

I tend to agree that we should also allow ‘small’ unbounded files without FSS if the sender ensures that they will be < 4GB.

If  there are no objections, I will integrate this change in my B6 draft.

Regards,
Felix

From: SIS-CFDPV1 <sis-cfdpv1-bounces at mailman.ccsds.org<mailto:sis-cfdpv1-bounces at mailman.ccsds.org>> On Behalf Of Wiegand, Robert E. (GSFC-5830) via SIS-CFDPV1
Sent: Friday, October 6, 2023 5:09 PM
To: sis-cfdpv1 at mailman.ccsds.org<mailto:sis-cfdpv1 at mailman.ccsds.org>
Subject: [SIS-CFDPV1] CFDP unbounded transfers

Greetings,

I have a comment/question regarding unbounded file transfers.

CCSDS 727.0-B-5 says in Table 5-1: Fixed PDU Header Fields

… All files of unbounded size shall be flagged ‘large’…

If the sender can ensure the unbounded file being transferred will be of size < 4GB, why must the sender/receiver use FSS size 64 bits for all PDUs?

Disadvantages:

-         each FDU 32 bits larger;

-         NAK sequence nearly doubles in size;

-         hardware/software built for 32 bit FSS cannot use unbounded file transfers

I am not seeing advantages that cannot be addressed without this constraint.

Any thoughts or explanation?
thank you
bob

--
Bob Wiegand
Ground Software Systems Branch
NASA/GSFC Code 583

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