[IPFIX] Full or Truncated EHs RE: Some comments on draft-ietf-opsawg-ipfix-tcpo-v6eh

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Hi Éric,

"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)."

I think that it would be simple to return that in a separate IE. Please refer to the proposal at: Extended TCP Options and IPv6 Extension Headers IPFIX Information Elements (boucadair.github.io)<https://boucadair.github.io/ipfix-tcpoptions-and-v6eh/draft-ietf-opsawg-ipfix-tcpo-v6eh.html#name-ipv6extensionheaderslimit-i>.

The absence of this IE is an indication that any EH-related IE reflect the full set of enclosed EHs.

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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