[Sis-dtn] BPv7/LTP binding issues

[Felix Flentge]

Hi Brian & All,

Good point: currently we have in IANA:

[cid:image001.png at 01DA7466.80992FA0]

And SANA:
[cid:image002.png at 01DA7466.80992FA0]

We may be able to argue that '1' is BPv6 as it points to RfC 5050, so maybe it is possible to have '4' for aggregated BPv7 bundles (or 4 for non-aggregated and 5 for aggregated bundles?).
'1' would mean LTP according to CCSDS 734.2-B-1 and 4 (+5?) would be defined in CCSDS 734.2-B-2 (I think IETF never formally standardised LTPCL, or?).

I probably also need to define to use '3' in the updated CFDP UT Layer Magenta Book (also, to my knowledge, nothing has been formally syandardised before, so it should be fine to have aggregation of CFDP PDU there).

And yes, makes sense to have the bundles as definite-length CBOR Byte Strings.

Regards,
Felix

From: SIS-DTN <sis-dtn-bounces at mailman.ccsds.org> On Behalf Of Sipos, Brian J. via SIS-DTN
Sent: Monday, March 11, 2024 1:56 PM
To: sis-dtn at mailman.ccsds.org
Subject: [Sis-dtn] BPv7/LTP binding issues

All,
I hadn't looked into the convergence layers section of the draft BPv7 blue book [1] earlier, and understand that these comments are coming late in the draft process.

The requirements in Section B2.1.4 "LTP Convergence Layer Adapter" currently don't actually specify which LTP Client Service ID is to be used for this CLA and because this "multiple bundles within a block" encoding scheme is different than what is defined for Client Service code point 1, I think that a new Client Service code point needs to be allocated for this encoding. It would also be valuable for a decoder to understand whether this encoding form allows only BPv7 bundles to be present or also v6 (or even a mix of the two). These are all considerations that if left unspecified will lead to interoperability failures.

Separate from the Client Service ID, the notion of a "length prefixed set of bytes" within CBOR is actually how the byte string major type [4] operates and this encoding seems like it would be better understood by encoders and decoders as a byte string type. In fact, this pattern of CBOR-within-byte-string is common enough that there is both CDDL schema for it as well as CBOR diagnostic notation for it. This second comment is less of an interoperability issue and more of a way to stick to existing tooling conventions for handling bstr-embedded CBOR.

The CDDL for this would be something like:
bp-in-block = (+bundle-bytes) ; encoded as a CBOR sequence
bundle-bytes = bstr .cbor bundle
; where "bundle" symbol is from Appendix B of RFC 9171

and the diagnostic notation is to enclose items with "<<" and ">>" brackets [5].

Thanks for any consideration,
Brian S.

[1] https://public.ccsds.org/review/CCSDS%20734.2-P-1.1/734x2p11e1.pdf
[2] https://www.iana.org/assignments/ltp-parameters/ltp-parameters.xhtml#client-service-ids
[3] https://sanaregistry.org/r/ltp_serviceid/
[4] https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1-2.5
[5] https://www.rfc-editor.org/rfc/rfc8610#appendix-G.3

This message is intended only for the recipient(s) named above. It may contain proprietary information and/or protected content. Any unauthorised disclosure, use, retention or dissemination is prohibited. If you have received this e-mail in error, please notify the sender immediately. ESA applies appropriate organisational measures to protect personal data, in case of data privacy queries, please contact the ESA Data Protection Officer (dpo at esa.int).
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.ccsds.org/pipermail/sis-dtn/attachments/20240312/07a6be98/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 73000 bytes
Desc: image001.png
URL: <http://mailman.ccsds.org/pipermail/sis-dtn/attachments/20240312/07a6be98/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.png
Type: image/png
Size: 22316 bytes
Desc: image002.png
URL: <http://mailman.ccsds.org/pipermail/sis-dtn/attachments/20240312/07a6be98/attachment-0003.png>