Re: [IPFIX] Bitfields vs. Unsigned RE: Re: WG LC: IPFIX documents

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Hi Paul,

Unless I'm mistaken, I didn't see any follow-up to this issue.

May I consider this point as closed? Thanks.

Cheers,
Med

De : BOUCADAIR Mohamed INNOV/NET
Envoyé : mardi 23 janvier 2024 14:23
À : 'Aitken, Paul' <[e-mail]>; Aitken, Paul <paitken=[e-mail]>; Joe Clarke (jclarke) <jclarke=[e-mail]>; [e-mail]
Cc : [e-mail]; [e-mail]; [e-mail]; [e-mail]
Objet : Bitfields vs. Unsigned RE: Re: [IPFIX] WG LC: IPFIX documents

Hi Paul,

> It is consistent but wrong, as the numeric value of these fields is meaningless. Bitfields with flags semantics don't have a meaningful "unsigned" value.

You raised this comment for both TCP/UDP specs.

As I mentioned in the previous message, all existing IEs of type flags are using an unsigned type. Also, please note that rfc7012#section-3.2.5 says the followings:

   "flags" is an integral value that represents a set of bit fields.
   Logical operations are appropriate on such values, but other
   mathematical operations are not.  Flags MUST always be of an unsigned
   data type.

And rfc7012#section-3:

   Abstract data types unsigned8, unsigned16, unsigned32, unsigned64,
   signed8, signed16, signed32, and signed64 are integral data types.
   As described in Section 3.2, their data type semantics can be further
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   specified, for example, by 'totalCounter', 'deltaCounter',
   'identifier', or 'flags'.
                 ^^^^^^^^^^

I quite don't understand why we need to define Bitfields rather than leveraging on the approach followed so far in IPFIX.

Cheers,
Med

De : Aitken, Paul <[e-mail]<mailto:[e-mail]>>
Envoyé : lundi 22 janvier 2024 11:49
À : BOUCADAIR Mohamed INNOV/NET <[e-mail]<mailto:[e-mail]>>; Aitken, Paul <paitken=[e-mail]<mailto:paitken=[e-mail]>>; Joe Clarke (jclarke) <jclarke=[e-mail]<mailto:jclarke=[e-mail]>>; [e-mail]<mailto:[e-mail]>
Cc : [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Objet : Re: Re: [IPFIX] WG LC: IPFIX documents

Med,

   The IE specified in Section 4.1 uses the new abstract data type
   defined in [I-D.ietf-opsawg-ipfix-tcpo-v6eh].

The unsigned256 type? It makes more sense to introduce a bitfield type.
[Med] I think the use of unsigned256 is consistent with the current use in IP Flow Information Export (IPFIX) Entities (iana.org) [iana.org]<https://urldefense.com/v3/__https://www.iana.org/assignments/ipfix/ipfix.xhtml__;!!OSsGDw!PbyTGwK6ng1xsDx7EDsqY-zP5SN-siBTe9ltLeN6whqtHew5I4J3MgqA7QOaYGnkTWnF4w1wMldDkBYIpjb9XwrB$> (where unsigned8, unsigned16, unsigned32, and unsigned64 are used for IEs having data semantic of flags.

It is consistent but wrong, as the numeric value of these fields is meaningless. Bitfields with flags semantics don't have a meaningful "unsigned" value.
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