Re: [Pce] WG Adoption of draft-li-pce-pcep-pmtu-05

Hi Shuping,

Please check inline below.

On Thu, Apr 7, 2022 at 8:22 AM Pengshuping (Peng Shuping) <
pengshuping@huawei.com> wrote:

> Hi Ketan,
>
>
>
> Thank you for your comments. Regarding to your three points, please find
> our responses below.
>
>
>
> 1)      Are you referring to an architecture kind of draft on Path MTU?
> Including collection, calculation/comparison, selection, enforcement to the
> headend?
>
KT> It starts from the definition and applicability of PMTU for SR
Policies. How is the (reducing) label stack factored in for SR-MPLS? How
does it apply for SRv6? Since in SRv6 we are actually doing encapsulation
(H.encap.*), is there fragmentation done? How are errors handled/reported?
Unlike RSVP-TE, with SR the "path" is not "nailed" down link-by-link and we
do have ECMP (not "multipath" that the draft refers to) where IGP routing
is followed. How is PMTU measured in such cases? Consider an SR Policy
which is a single FlexAlgo Prefix-SID of the destination - what would be
the PMTU of such an SR Policy? It also includes the aspects you mention.
These are not specific to PCEP protocol and also apply when provisioning is
done via BGP SRTE.

> We are open to have such draft but would like to get the guidance from the
> Chairs of these working groups whether it is needed since there have been
> several PMTU drafts adopted already in each WG. But we don’t think this
> should be taken as a reason to stop the adoption of this draft because it
> has all the information that needs to be adopted in the PCE WG.
>
KT> I have a concern with protocol extensions and encodings being defined
without the applicability, use-case, architecture, and design being ironed
out first.

>
>
> 2)      In PCEP, the METRIC object as per RFC5440 is used for both a) and
> b). In this draft, we defined a new type of METRIC object.
>
KT> Please point me to the text in the document where both these
use-cases/scenarios are described. Have I missed it?

Thanks,
Ketan

>
>
> 3)      Yes, this is applicable for both RSVP-TE and SR Policy.
>
>
>
> Thank you!
>
>
>
> Best Regards,
>
> Shuping
>
>
>
>
>
>
>
> *From:* Ketan Talaulikar [mailto:ketant.ietf@gmail.com]
> *Sent:* Monday, April 4, 2022 10:05 PM
> *To:* Dhruv Dhody <dd@dhruvdhody.com>
> *Cc:* pce@ietf.org; draft-li-pce-pcep-pmtu@ietf.org
> *Subject:* Re: [Pce] WG Adoption of draft-li-pce-pcep-pmtu-05
>
>
>
> Hello,
>
>
>
> I do not believe this document is ready for adoption. I believe the WG
> perhaps needs to discuss some basic concepts before taking up this work.
>
>
>
> Please note that I do not object to (what I infer is) the motivation for
> this work. This document is not (yet) a good starting point for this work.
>
>
>
> 1) We need a SPRING WG document that covers the considerations related to
> Path MTU for SR Policies. We do not have such a document today. While this
> document does touch upon certain aspects, it is inadequate. This document
> should focus more on the PCEP protocol aspects and rely on the existing
> RSVP-TE spec RFC3209 and TBD for SR Policy for the application to the
> respective constructs. Note that draft-ietf-idr-sr-policy-path-mtu
> introduces this PMTU for BGP SRTE [*]
>
>
>
> 2) There seems to be some degree of mixup between the concept of (a)
> constraint for the path and (b) the reporting of the calculated path MTU of
> the path. Both are perhaps needed, but we need them to be unambiguous and
> differentiated. I would think that (a) is also very useful. And I am not
> sure if it is appropriate to refer to (b) as a "metric" - isn't it a
> property?
>
>
>
> 3) This is applicable for both RSVP-TE and SR Policy.
>
>
>
> [*] What I see is that some amount of uncoordinated protocol spec
> development related to SPRING constructs is happening in the
> protocol-specific WGs (PCE & IDR) without the base work being done in the
> SPRING WG. I had raised this point during the IDR document adoption as
> well:
> https://mailarchive.ietf.org/arch/msg/idr/ZrN1-Uw1ggyxKeltBICmcthjymM/
>
>
>
> Thanks,
>
> Ketan
>
>
>
>
>
>
>
> On Mon, Mar 28, 2022 at 9:40 PM Dhruv Dhody <dd@dhruvdhody.com> wrote:
>
> Hi WG,
>
> This email begins the WG adoption poll for draft-li-pce-pcep-pmtu-05.
>
>
>
> https://datatracker.ietf.org/doc/draft-li-pce-pcep-pmtu/
>
>
>
> Should this draft be adopted by the PCE WG? Please state your reasons -
> Why / Why not? What needs to be fixed before or after adoption? Are you
> willing to work on this draft? Review comments should be posted to the list.
>
> Please respond by Monday 11th April 2022.
>
> Thanks!
> Dhruv & Julien
>
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>