[IPFIX] count of EHs (RE: Some comments on draft-ietf-opsawg-ipfix-tcpo-v6eh

[[e-mail]]

Re-,

Focusing on this part of your comments:

==
About having counters per extension header how is "This Information Element echoes the order and number of occurrences" to be interpreted for the following flow?

HBH-RH-DST
HBH-DST-RH-FRA0-DST
HBH-DST-RH-FRA1-...
RH-DST

Will it be a single IE with HBH=3, DST=5, RH=3, FRA0=1, FRA1=1 or 4 IE exported (one for each chain) ?

I think that the 4 IE sounds more logical and useful, then there is no need to count the occurrences of one specific EH but more how often a specific EH chain was seen.
==

Yes, I confirm that 4 IEs will be exported.

The count is still needed to report cases where an EH appear multiple times in the same chain. Updated the text to insist the count is related to consecutive occurrences, though:

OLD:
   Description:  As per [RFC8200], IPv6 nodes must accept and attempt to
      process extension headers in occurring any number of times in the
      same packet.  This Information Element echoes the order and number
      of occurrences of the same extension header instance in an IPv6
      packet.

NEW:

   Description:  As per Section 4.1 of [RFC8200], IPv6 nodes must accept

      and attempt to process extension headers in occurring any number

      of times in the same packet.  This Information Element echoes the

      order of extension headers and number of consecutive occurrences

      of the same extension header type in an IPv6 packet.



      The same extension header type may appear several times in an

      ipv6ExtensionHeaderCount Information Element (see Section 4.1 of

      [RFC8200].  For example, if an IPv6 packet includes a Hop-by-Hop

      Options header, a Destination Options header, a Fragment header,

      and Destination Options header, the ipv6ExtensionHeaderCount

      Information Element will report two counts of the Destination

      Options header: the occurrences that are observed before the

      Fragment header and the occurrences right after the Fragment

      header.

Cheers,
Med

De : OPSAWG <[e-mail]> De la part de Eric Vyncke (evyncke)
Envoyé : vendredi 6 octobre 2023 14:49
À : [e-mail]
Cc : [e-mail]
Objet : [OPSAWG] Some comments on draft-ietf-opsawg-ipfix-tcpo-v6eh

Benoît and Med,

Thanks for this useful document, please find below some comments (obviously without any hat).

Should the "No Next-Header" (next-header=59) be included (cfr my other remarks on the companion I-D) ?

There should be a way to convey the information that the exporter was (un)able to parse the *full* extension header chain due to HW limitation. This could be done by adding a bit/counter "KNOWN" (the opposite of UNKNOWN in the sense of a known layer-4 header).

About having counters per extension header how is "This Information Element echoes the order and number of occurrences" to be interpreted for the following flow?

HBH-RH-DST
HBH-DST-RH-FRA0-DST
HBH-DST-RH-FRA1-...
RH-DST

Will it be a single IE with HBH=3, DST=5, RH=3, FRA0=1, FRA1=1 or 4 IE exported (one for each chain) ?

I think that the 4 IE sounds more logical and useful, then there is no need to count the occurrences of one specific EH but more how often a specific EH chain was seen.

I still wonder why the tcpOptions and ipv6ExtensionHeaders are in the same I-D though ;-)

Hope this helps,

-éric

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