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

[Rakesh Gandhi <[e-mail]>]

Thanks Andy, Loa and Greg.
Acking, we can go with a similar ACH based proposal.

Thanks,
Rakesh


On Mon, Dec 28, 2020 at 2:05 PM Andrew G. Malis <[e-mail]> wrote:

> 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 <[e-mail]>
> 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 <[e-mail]> 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
>>> >
>>> >
>>> > _______________________________________________
>>> > mpls mailing list
>>> > [e-mail]
>>> > https://www.ietf.org/mailman/listinfo/mpls
>>> >
>>>
>>> --
>>>
>>> Loa Andersson                        email: [e-mail]
>>> Senior MPLS Expert                          [e-mail]
>>> Bronze Dragon Consulting             phone: [phone]
>>>
>>> _______________________________________________
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