[SIS-CFDPV1] [EXTERNAL] [BULK] Re: CFDP unbounded transfers

[Wiegand, Robert E. (GSFC-5830)]

The large file flag and segment metadata added by CCSDS 727.0-B-5 certainly affected some content field locations / sizes. AFAICT, allowing large file flag 0 for small unbounded files does not further complicate the header parsing or content processing.

My guess was that the reason for the constraint was to prevent the ‘large file’ flag from being changed during a transaction (which I think is wise).

regards
bob



From: Deaton, Joshua E. (MSFC-HP27)[MOSSI2] <joshua.e.deaton at nasa.gov>
Sent: Wednesday, October 11, 2023 8:45 AM
To: Felix Flentge <Felix.Flentge at esa.int>; Wiegand, Robert E. (GSFC-5830) <robert.e.wiegand at nasa.gov>; sis-cfdpv1 at mailman.ccsds.org
Subject: RE: [EXTERNAL] [BULK] Re: [SIS-CFDPV1] CFDP unbounded transfers

Does this cause any problems for high speed implementations? I thought one of the reasons for the fixed header fields was that you could directly parse the header with no other knowledge thereby speeding up the act of processing the PDU.

From: SIS-CFDPV1 <sis-cfdpv1-bounces at mailman.ccsds.org<mailto:sis-cfdpv1-bounces at mailman.ccsds.org>> On Behalf Of Felix Flentge via SIS-CFDPV1
Sent: Wednesday, October 11, 2023 2:07 AM
To: 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>
Subject: [EXTERNAL] [BULK] Re: [SIS-CFDPV1] CFDP unbounded transfers

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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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