Re: [Tsv-art] Tsvart early review of draft-ietf-opsawg-ipfix-tcpo-v6eh-05

[[e-mail]]

Hi Wes,

Please see inline.

Cheers,
Med

De : Wesley Eddy <[e-mail]>
Envoyé : mardi 16 janvier 2024 16:09
À : BOUCADAIR Mohamed INNOV/NET <[e-mail]>; [e-mail]
Cc : [e-mail]; [e-mail]
Objet : Re: Tsvart early review of draft-ietf-opsawg-ipfix-tcpo-v6eh-05


The changes look good to me; I just want to make sure you understand one of my questions that doesn't look like it was clear enough:
On 1/15/2024 4:13 AM, [e-mail]<mailto:[e-mail]> wrote:

- The way an implementation understands the TCP ExIDs may benefit

from slightly more explanation:

  -- In 4.2 and 4.3, is the idea that the implementation is just

sampling the

  16 or 32 bits following the experimental option kind being

indicated, and

  assuming those 2 or 4 bytes to be ExIDs?  From Section 6.2, I

got the sense

  that the implementation is aware of particular ExID values

specifically, to

  know if they should be reported as 2 or 4 byte values.

[Med] 2-byte IDs are reported in tcpSharedOptionExID16 while 4-byte IDs are reported in tcpSharedOptionExID32.
Are you expecting the implementation to have an exhaustive list of all of the ExIDs in use to understand the difference between 2 and 4 byte usage?
[Med] Yes because otherwise an implem can’t unambiguously identify and extract ExIDs. We do provide a pointer to the registered ExIDs:

==
Additional Information:  See assigned ExIDs at [IANA-TCP-EXIDs].
==

Please let me know if you still think a clarification is needed to the draft. Thanks.

  I don't quite understand how this is supposed to work at the sampling point, since it's the TCP implementation that interprets the option and determines whether it is to be interpreted as containing (1) no ExID, (2) a 16-bit ExID, (3) a 32-bit ExID.  This information is not available within the protocol to a third party.  The third party would need a list of ExIDs in-use in order to understand them.
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