Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-ioam-sr-04

Greg,

Thanks for the reminder! This is basically what I had in mind when I
suggested using the ACH.

Cheers,
Andy

On Mon, Dec 28, 2020 at 12:31 PM Greg Mirsky <gregimirsky@gmail.com> wrote:

> Hi Loa, Andy, et al.,
> I think that if someone is interested in how a similar problem (as I
> understand what IOAM tries to achieve) was resolved, RFC 8169
> <https://datatracker.ietf.org/doc/rfc8169/?include_text=1> might have
> useful information. We've used ACH, Scratch Pad for collecting telemetry
> (residence time), and TLV to carry the original PTP packet through the MPLS
> domain.
>
> Regards,
> Greg
>
> On Sun, Dec 27, 2020 at 11:04 PM Loa Andersson <loa@pi.nu> wrote:
>
>> Working Group,
>>
>> Andy and I have discussed this a bit off-line.
>>
>> Andy,
>>
>> I have now re-read the this  draft, other relevant drafts and the mail
>> we have exchanged. I had earlier partly misunderstood and now think that
>> your summary of the situation is basically correct.
>>
>> However, I'd like to see more discussion on what we should do. In
>> particular I'd like to see a comment from the authors on this.
>>
>> You outline three different proposals:
>>
>> 1.  follow the draft and allocate 0x0010b from IP Version Numbers
>>      registry in the Version Numbers name space for this purpose
>> 2.  use ACH
>> 3.  use code point #15 from IP Version Numbers registry in the Version
>>     Numbers name space
>>
>> To me it seems like 1 and 3 is the same, we ask for a code point from IP
>> Version Numbers registry in the Version Numbers name space. IANA pick
>> the code point for us.
>>
>> Note 1: We can give a strong recommendation telling IANA which code
>> point we want, but the decision is still with IANA.
>>
>> Note 2: It seems like the chances that a Version number lower than 6
>> will not be picked for an IP version, value 2 is unassigned and much
>> easier to allocate than the reserved value 15.
>>
>> Note 3: I think you are right that it is a hrd sell both to working
>> group and the IESG to pick a value from this registry.
>>
>> Authors.
>>
>> It would be nice to hear from you on this discussion, but don't change
>> the document until we have a reasonable consensus.
>>
>> /Loa
>>
>>
>>
>> On 25/12/2020 01:44, Andrew G. Malis wrote:
>> > I've been asked to provide a pre-adoption MPLS-RT review of
>> > draft-gandhi-mpls-ioam-sr-04.
>> >
>> > I have a major concern that I believe needs to be addressed, either
>> > before or after WG adoption (I defer to the WG chairs to make this
>> > decision). My personal preference is that it be addressed by the
>> authors
>> > prior to adoption, but if it occurs following adoption, I would like to
>> > see it addressed before it gets much further in the WG process.
>> >
>> > My concern is as follows:
>> >
>> > In Section 6 and Figure 1, 0x0010b (2 decimal) is used for the first
>> > nibble following the MPLS label stack in order to avoid ECMP. This
>> > intent is fine, but there is an issue with choosing this particular
>> > value. The first nibble following the label stack is often (as we know)
>> > interpreted as an IP Version Number. According to
>> > https://www.iana.org/assignments/version-numbers/version-numbers.xhtml
>> > <https://www.iana.org/assignments/version-numbers/version-numbers.xhtml>
>>
>> > , 0x0010b (2 decimal) is currently unassigned, so it COULD be assigned
>> > by IANA, creating a future conflict.
>> >
>> > We could request IANA to assign IP Version number 2 for this purpose,
>> > but I believe that would be a very difficult sell to both IANA and the
>> > IESG, as there are only a small number of IP Version numbers available.
>> >
>> > Instead, I would suggest either of the two following alternatives:
>> >
>> > 1. Use the MPLS ACH (RFC 5586), starting with 0x0001b, and alter the
>> > packet format in Figure 1 of this draft accordingly so that it follows
>> > the ACH's general format but also includes the necessary fields for the
>> > draft's purpose.
>> >
>> > 2. Use one of the IANA reserved IP version numbers instead of 0x0010b.
>> I
>> > would recommend 15 (0x1111b). There is reasonable certainty that this
>> > would never actually ever be assigned by IANA.
>> >
>> > The first alternative is my personal preference, but I would be OK with
>> > the second as well.
>> >
>> > Other comments:
>> >
>> > Other than this issue, I found the draft to be well-written and easy to
>> > follow, and generally ready for WG adoption.
>> >
>> > Cheers,
>> > Andy
>> >
>> >
>> > _______________________________________________
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>> >
>>
>> --
>>
>> Loa Andersson                        email: loa@pi.nu
>> Senior MPLS Expert                          loa.pi.nu@gmail.com
>> Bronze Dragon Consulting             phone: +46 739 81 21 64
>>
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