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

From: Dhruv Dhody <[email-masked]>
Date: Mon, 15 Jul 2019 20:57:19 +0530

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).

--

(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.

--

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

---

From: <[email-masked]>
Date: Wed, 17 Jul 2019 11:13:23 +0800 (CST)

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:

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.

(2) Path Segment:

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.

Thanks,
Dhruv

---

From: Dhruv Dhody <[email-masked]>
Date: Fri, 19 Jul 2019 10:18:04 -0400

Hi Quan,

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

> <<would be nice if they could be clarified before hand.
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.

> 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

> [2]
> https://tools.ietf.org/id/draft-xiong-spring-path-segment-sr-inter-domain-00.txt

---

From: <[email-masked]>
Date: Tue, 23 Jul 2019 16:52:20 +0800 (CST)

Hi Dhruv,

Thanks for your reply! My clarification is as follows tagged with Quan>>.

Best Regards,

Quan

原始邮件

发件人：DhruvDhody <[email-masked]>
收件人：熊泉00091065;
抄送人：[email-masked] <[email-masked]>;[email-masked] <[email-masked]>;[email-masked] <[email-masked]>;
日 期 ：2019年07月19日 22:19
主 题 ：Re: Quick Review of SR Inter-domain and association

Hi Quan, 

Hi Dhruv,

Best Regards,

Quan

<<Hi Authors,

--

(1) Association:

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.

Quan>> Once the association is created, the parent PCE sends PCInitailte/PCUpd message to child PCEs. Then the child PCEs will configure this

association  to the ingress nodes and related LSPs in each domain.  For example, when the LSP-1 reaches node X along SR path , the node X will find the association  which the LSP-1 belongs  and forward the packets to the LSP-2 which belongs to the same association.

(2) Path Segment:

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. 

Quan>> Yes, we have proposed another use case draft in Spring WG. This draft in PCE WG is the solution for it. We hope to get consensuses in Spring and Pce WGs at the same time. We use path segment to provide the SR end-to-end bidirectional path. The Path Segment is used to correlate the inter-domain paths and foward and reverse unidirectional paths in SR label stack. 

Safe Travels! 

Thanks! 

Dhruv 

Thanks,
Dhruv