Re: [Pce] Quick Review of SR Inter-domain and association

[Dhruv Dhody <[e-mail]>]

Hi Quan,

First of all thanks for your reply to the list...

On Wed, Jul 17, 2019 at 8:43 AM <[e-mail]> wrote:

>
> Hi Dhruv,
>
>
> Thanks for your review and suggestions! It is very appreciated!
>
> My clarification is as follows tagged with Quan>>.
>
>
> Best Regards,
>
> Quan
>
>
> <<Hi Authors,
>
> <<I did a quick review of the I-Ds, but some key questions came up, it
> <<would be nice if they could be clarified before hand.
>
> --
>
> (1) Association:
>
> It is important to describe where this association exist and what role
> does that play, to me the importance of the association is at the
> Parent PCE only and thus the existing Stateful H-PCE [1] procedures
>
> should be enough IMHO.
> See figure 2 in your I-D, ASSOC 1 LSPs are distributed between all the
> other child PCEs and thus not at clear why a child PCE need to be
> aware of the association when it does not know any other LSP (outside
>
> of its domain, that are part of the same association group).
>
>
> Quan>>I agree with you and thanks for your suggestion. The Stitching LSP
>
> association is created and maintained at parent PCE. The Stitching LSP
>
> association is used in inter-Area scenario. The association is useful
> when the
>
>  LSPs from multiple domains are aready created and the parent PCE may
>
>  associate them into a group and achieve the end-to-end LSP. I will
> update
>
> and clarify the use case and the detailed operation  as following shown.
>
>
>
>
Dhruv: The key question is why does the child PCE (PCE-1,2,3) needs to be
aware of this association once it is created at the parent PCE? In other
words what do you expect the child PCE to do when it receives a PCUpd
message with the association information? Answering this question would
help to clarify the need.

>
> (2) Path Segment:
>
> I saw the spring I-D [2] as well, and was thrown by the use of path
> segment as a way to stitch. My gut feeling was isn't that more like a
> binding segment? Also for stitching label in PCE, please check
> Olivier's I-D [3].
> So, some clarity on what exactly you would like to achieve and the
> reason behind the use of association and path segment is required.
>
> Quan>>I have compared my draft with [3] before. I think my draft focus on
>
> the SR inter-domain scenario and provide end-to-end solution with path
>
> segment. The path segment is the path identifier and it can be used to
>
> correlate SR paths. When the path segment is used to correlate two
>
> inter-domain LSPs, it is used as a stitching label and the path segment
>
> in SR networks can be viewed as an instantiation or specific application
>
> for the stitching label which proposed in draft[3]. The path segment used
>
> as a stitching label in inter-AS scenario as following shown.
>
>
>
Dhruv: I understand what you want to achieve, but I am not able to grasp
why use Path segment for it. Anyways the use of path segment in this way
should get consensuses in SPRING WG first.

Safe Travels!

Thanks!
Dhruv


>
> I hope you would focus on these aspects during your presentation.
> Discussion on the list would be even better.
>
> Thanks,
> Dhruv
>
> [1] https://tools.ietf.org/html/draft-ietf-pce-stateful-hpce-11
> [2]
> https://tools.ietf.org/id/draft-xiong-spring-path-segment-sr-inter-domain-00.txt
> [3] https://tools.ietf.org/html/draft-dugeon-pce-stateful-interdomain-02
>
>
>