[Sls-sea-dls] SDLS EP Minor Issues

[David Koisser (external)]

Hello everyone,

While working on the interoperability test John and me noticed some minor 
issues in the baseline of the current draft. 
See the list below including suggestions for straight-forward fixes:

- The Rekey SA has two possible PDUs under the same Tag (TC case and TM 
case): This makes processing ambiguous without looking up the SPI as well 
as its assigned channels OR implying from the length field. Further, it is 
not clear why the TM version still needs two Key-IDs as well as both IV 
and ARSN (doesn't USLP also work with AES-GCM?).
--> Suggestion: Two PDUs with the same structure, e.g., TC: SPI, Auth-Key, 
ARSN (96 Bit with padding) and TM: SPI, Encr-Key, IV.(OR all four fields 
for both)

- The Read ARSN also has two possible PDUs under the same Tag.
--> Suggestion: Making the ARSN field 96 Bits (with padding).

- The Start SA PDU only shows one Tag: The third Tag field can be either 
'01' or '10', depending on up- or downlink. (also, there can be no mix 
between both types of GVCIDs)
--> Suggestion: State that the Tag changes when addressing downlink.

- The Read ARSN Reply PDU has no SPI: This makes the procedure implicitly 
stateful, meaning it cannot be interpreted on its own and on multiple 
requests the order must be considered.
--> Suggestion: Include the SPI as well.

Cheers,
David
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