Re: [ippm] New Version Notification for draft-ahuang-ioam-on-path-delay-00.txt

[Justin Iurman <[e-mail]>]

Hi Greg,

On 3/3/23 22:17, Greg Mirsky wrote:
> Hi, Alex, Justin et al.,
> I read the draft and have some notes to share with you:
> 
>   * I think that I understand the motivation of the authors of the
>     draft. RFC 9197 does not specify when the timestamp SHOULD (less,
>     MUST) be taken. As a result, it is challenging to extract variable

True, "the time at which the packet was received by the node" 
([RFC9197]) can be vague, although all devices of an IOAM-Domain are 
expected to follow the same definition. But, then...

>     [...] Have you
>     considered using Bit 4 Transit delay as defined in RFC 9197?

... bit 4 Transit Delay has the same issue, i.e., RFC 9197 does not 
specify exactly when the ingress/egress timestamps SHOULD/MUST be taken. 
Besides, this data field is quite often hard to retrieve (and by "hard", 
I mean from a performance point of view).

Thanks,
Justin

> Regards,
> Greg
> 
> On Fri, Mar 3, 2023 at 10:52 AM Justin Iurman <[e-mail] 
> <mailto:[e-mail]>> wrote:
> 
>     Hi Alex,
> 
>     I don't understand why bits 2 and 3 (i.e., timestamp seconds &
>     fraction)
>     are not enough. If each node on the path timestamps its data part in
>     the
>     trace, then based on the entire trace you're able to recompute on-path
>     delays by simply substracting a node's timestamp by the one of the
>     encapsulating node. You can actually compute the on-path delay between
>     any node. Did I miss something?
> 
>     Thanks,
>     Justin
> 
>     On 3/3/23 17:54, Alex Huang Feng wrote:
>      > Dear IPPM WG,
>      >
>      > Some time ago I submitted draft-ahuang-ippm-dex-timestamp-ext that
>      > allows IOAM DEX to add a timestamp in the header.
>      > This allows IOAM in postcard mode to compute the on-path delay at
>     each node.
>      >
>      > To export the on-path delay in the IOAM architecture, a bit-field
>     is used.
>      > This new draft adds a new 32bit Data-field in the "IOAM Trace-Type”
>      > registry allowing the export of the On-path delay in the IOAM
>     architecture.
>      >
>      > I would like to request feedback from the WG on this draft.
>      >
>      > Cheers,
>      > Alex
>      >
>      >> On 3 Mar 2023, at 17:40, [e-mail]
>     <mailto:[e-mail]>
>      >> <mailto:[e-mail]
>     <mailto:[e-mail]>> wrote:
>      >>
>      >>
>      >> A new version of I-D, draft-ahuang-ioam-on-path-delay-00.txt
>      >> has been successfully submitted by Alex Huang Feng and posted to the
>      >> IETF repository.
>      >>
>      >> Name:draft-ahuang-ioam-on-path-delay
>      >> Revision:00
>      >> Title:On-Path delay Data Field for In Situ Operations,
>     Administration,
>      >> and Maintenance (IOAM)
>      >> Document date:2023-03-03
>      >> Group:Individual Submission
>      >> Pages:7
>      >> URL:
>      >>
>     https://www.ietf.org/archive/id/draft-ahuang-ioam-on-path-delay-00.txt <https://www.ietf.org/archive/id/draft-ahuang-ioam-on-path-delay-00.txt>
>      >>
>     <https://www.ietf.org/archive/id/draft-ahuang-ioam-on-path-delay-00.txt <https://www.ietf.org/archive/id/draft-ahuang-ioam-on-path-delay-00.txt>>
>      >> Status:
>      >>
>     https://datatracker.ietf.org/doc/draft-ahuang-ioam-on-path-delay/
>     <https://datatracker.ietf.org/doc/draft-ahuang-ioam-on-path-delay/>
>      >>
>     <https://datatracker.ietf.org/doc/draft-ahuang-ioam-on-path-delay/
>     <https://datatracker.ietf.org/doc/draft-ahuang-ioam-on-path-delay/>>
>      >> Htmlized:
>      >>
>     https://datatracker.ietf.org/doc/html/draft-ahuang-ioam-on-path-delay <https://datatracker.ietf.org/doc/html/draft-ahuang-ioam-on-path-delay>
>      >>
>     <https://datatracker.ietf.org/doc/html/draft-ahuang-ioam-on-path-delay <https://datatracker.ietf.org/doc/html/draft-ahuang-ioam-on-path-delay>>
>      >>
>      >>
>      >> Abstract:
>      >>   This document defines a Data Field In Situ Operations,
>      >>   Administration, and Maintenance (IOAM) architecture for
>     on-path delay
>      >>   information.  This data field is registered as a new entry in the
>      >>   "IOAM Trace-Type" registry.
>      >>
>      >>
>      >>
>      >>
>      >>
>      >> The IETF Secretariat
>      >>
>      >>
>      >
>      >
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