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

[Wesley Eddy <[e-mail]>]

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] 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?  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.