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

[Gyan Mishra <[e-mail]>]

Hi Ketan

Please see in-line below Gyan2.

On Thu, Apr 21, 2022 at 10:32 AM Ketan Talaulikar <[e-mail]>
wrote:

> Hi Gyan,
>
> Please check inline below with KT2.
>
>
> On Thu, Apr 21, 2022 at 1:07 AM Gyan Mishra <[e-mail]> wrote:
>
>> Hi Ketan
>>
>> Please see in-line
>>
>> Thanks
>>
>> On Wed, Apr 20, 2022 at 7:10 AM Ketan Talaulikar <[e-mail]>
>> wrote:
>>
>>> Hi Gyan,
>>>
>>> Please check inline below.
>>>
>>>
>>> On Wed, Apr 20, 2022 at 10:08 AM Gyan Mishra <[e-mail]>
>>> wrote:
>>>
>>>>
>>>> Hi Ketan
>>>>
>>>>
>>>> On Mon, Apr 4, 2022 at 10:05 AM Ketan Talaulikar <[e-mail]>
>>>> wrote:
>>>>
>>>>> 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 [*]
>>>>>
>>>>
>>>>     Gyan> As Spring SR Policy draft has already been submitted for
>>>> publication, could we add verbiage to the IDR SR Policy draft  and as this
>>>> draft  is BGP SR policy  related PCE extension for PMTUD similar to the IDR
>>>> SR policy PMTU draft mentioned.
>>>>
>>>
>>> KT> I do not see these mechanisms as being protocol specific and hence
>>> do not seem right for either PCEP or BGP documents.
>>>
>>
>>     Gyan> Understood.  So PMTU related protocol specific in the IDR and
>> PCEP documents and PMTU in SR policy specifics in a Spring Informational
>> document?
>>
>
> KT2> Yes.
>

>
>>
>>>
>>>> I read the comments from the IDR adoption call as it relates to SR and
>>>> PMTU.  I think  we all agree that the goal of this and the IDR drafts are
>>>> warranted.  However as PMTUD even as it relates to SR is not overly
>>>> complicated that we need a draft to explain what constitutes the total SR
>>>> packet size, as SR is not any different from any other technology from a
>>>> packet sizing perspective.   The same concept that the lowest MTU link
>>>> along a path is the maximum MTU  PMTU for the path is valid and that is the
>>>> basis for PMTU.  I don’t think this should hold up the adoption call.
>>>>
>>>
>>> KT> We've had this conversation in the IDR WG during the IDR document
>>> adoption and we don't yet have a SPRING document. I am not sure if the PCEP
>>> work proceeds in a similar manner. I will leave it to the WG chairs'
>>> judgment on this matter.
>>>
>>
>>     Gyan> I reviewed the mail archive on the discussion and your request
>> for a PMTU in SR policy Spring document.  I think this is an important
>> issue to be solved related to PMTU to prevent fragmentation for operators.
>>
>
> KT2> We have SR-MPLS and SRv6. For each of them, we have different kinds
> of payload - IPv4, IPv6, MPLS, Ethernet, etc. which have different
> characteristics when it comes to whether or not fragmentation can be
> performed at the SR Policy head-end.
>

    Gyan2> Understood.   So a design document that goes into the details
related to fragmentation on SR Policy head end SID list candidate path
instantiated and the impact of fragmentation on intermediate nodes.  The
goal of the IDR and PCE drafts is in solution space to prevent
fragmentation from happening using PMTU.  Fragmentation aspect of SR Policy
instantiation is the problem and I agree that should be in Spring WG and I
would be happy to collaborate on that draft.  I agree that SR Policy PMTU
should also be part of that Spring draft.

>
>
>> Would this draft go into the details of how fragmentation would work with
>> SR problem statement or would it just detail the PMTU protocol specific BGP
>> and PCEP  solution?
>>
>
> KT2> BGP and PCEP documents should be about their respective protocol
> signaling extensions. The realization and actual implementation of the SR
> Policy forwarding and path computation construct is common and perhaps
> outside of those signaling protocols. What I am looking for is a SPRING
> document that first defines what is a PMTU for an SR Policy, how is it
> computed, and then how MTU exceed conditions are handled.
>

    Gyan2> Understood. Makes sense. Agreed.

>
> If the authors of the PCEP draft published an informational draft on PMTU
>> in SR Policy as it relates to both IDR and PCE  drafts would that suffice?
>>
>
> KT2> Perhaps we need a standards-track document to specify the
> implementation behavior? Otherwise, how would one ensure interoperability
> between the controllers and head-end routers coming from different vendors?
> Everyone needs to have the same understanding of what the PMTU is and how
> things are to be handled.
>

    Gyan> Ack on standards track document to ensure interoperability.  I
can work with authors of the PCE and IDR drafts to start a Spring draft on
PMTU in SR Policy and fragmentation aspects.  The fragmentation issue is an
important issue, and as this is an adoption call we have time to finalize
once it becomes a WG document before WGLC, so I think we should proceed
with adoption to not slow down progress.  At the same time I can commit to
working with the authors of the IDR and PCE draft to start the new Spring
draft.  So the plan would be as well to get the Spring draft at a minimum
adopted and refined enough as far as PMTU definition that we can publish
the IDR and PCE drafts which would be further along.  As PMTU definition is
most important for the IDR and PCE draft, getting the fragmentation aspects
all figured out is important but should not hold up the IDR and PCE drafts
publication.  Most importantly the PMTU and fragmentation issue is a
critical issue to be solved, and so getting the solutions progressed is of
utmost importance for operators. (Understood that we have the cart before
the horse slightly but I think that can be corrected before WGLC and
publication)

>
> Thanks,
> Ketan
>
>
>
>>
>>> Thanks,
>>> Ketan
>>>
>>>
>>>>
>>>>> 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.
>>>>>
>>>>
>>>>     Gyan> Agreed
>>>>
>>>>>
>>>>> [*] 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 <[e-mail]> 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
>>>>>> _______________________________________________
>>>>>> Pce mailing list
>>>>>> [e-mail]
>>>>>> https://www.ietf.org/mailman/listinfo/pce
>>>>>>
>>>>> _______________________________________________
>>>>> Pce mailing list
>>>>> [e-mail]
>>>>> https://www.ietf.org/mailman/listinfo/pce
>>>>>
>>>> --
>>>>
>>>> <http://www.verizon.com/>
>>>>
>>>> *Gyan Mishra*
>>>>
>>>> *Network Solutions A**rchitect *
>>>>
>>>> *Email [e-mail] <[e-mail]>*
>>>>
>>>>
>>>>
>>>> *M 301 502-1347*
>>>>
>>>> --
>>
>> <http://www.verizon.com/>
>>
>> *Gyan Mishra*
>>
>> *Network Solutions A**rchitect *
>>
>> *Email [e-mail] <[e-mail]>*
>>
>>
>>
>> *M 301 502-1347*
>>
>> --

<http://www.verizon.com/>

*Gyan Mishra*

*Network Solutions A**rchitect *

*Email [e-mail] <[e-mail]>*



*M 301 502-1347*