Re: [Pce] Implementation option of draft-ietf-pce-stateful-interdomain-01.txt

Hi Olivier,

I would not recommend using the BSID TLV for #2 (Signal the presence of a Stitching Label in the path of a Tunnel/Policy). ERO/SR-ERO is the object that encodes the label-stack/path, and the SL is part of the label-stack/path of the previous Policy/Tunnel that uses it, so it belongs to the ERO/SR-ERO. BTW I don’t believe there is currently a way in PCEP to represent a BSID ERO sub-object, it would be useful to define it in some common way with the Stitching Label.

I agree about using flag(s) instead of allocating a new PST to represent the SL in the BSID TLV.

*IF* RSVP-TE RECORD_ROUTE is used, then RRO object is appropriate.

Thanks,
Mike.

From: olivier.dugeon@orange.com <olivier.dugeon@orange.com>
Sent: Tuesday, March 23, 2021 2:11 PM
To: Mike Koldychev (mkoldych) <mkoldych@cisco.com>; Stone, Andrew (Nokia - CA/Ottawa) <andrew.stone@nokia.com>; Dhruv Dhody <dhruv.ietf@gmail.com>
Cc: pce@ietf.org
Subject: Re: [Pce] Implementation option of draft-ietf-pce-stateful-interdomain-01.txt

Hi Mike,
Le 22/03/2021 à 21:03, Mike Koldychev (mkoldych) a écrit :
Hi Olivier,

I believe what you are trying to achieve is:

  1.  Attach a Stitching Label to a Tunnel/Policy, similar to how a Binding Label points to a Tunnel/Policy.
[OD] Yes. Exactly

  1.
  2.  Signal the presence of a Stitching Label in the path of a Tunnel/Policy.
[OD] Yes by using PCE to PCE exchange through PCEP to convey this information

  1.

I believe that #1 can be achieved using the Binding Label TLV, by perhaps defining another Binding Type. And #2 can be achieved by adding another ERO/SR-ERO sub-object.
[OD] I think that both #1 & #2 could be achieved using the TE-PATH-BINDING TLV minus the addition of new flag to mention that the TE-PATH-BINDING TLV transport a Stitching Label. I would not define a new Binding Type as we could re-use which have been already define in the pce-binding-sid draft and we would not go back to the same problem as with the multiple PST code point. So, a dedicated flag to mention that it is a Binding Label for inter-domain would be better.

I do not think it’s a good idea to use the RRO unless there is an actual RSVP RECORD_ROUTE being used.

[OD] I tend to be agree after analysis all potential inconvenient, in particular in term of management. But, in another hand, the Stitching label is part of the Tunnel path reported by the Record Route Object.

Regards

Olivier

Thanks,
Mike.

From: Pce <pce-bounces@ietf.org><mailto:pce-bounces@ietf.org> On Behalf Of Stone, Andrew (Nokia - CA/Ottawa)
Sent: Thursday, March 11, 2021 11:11 AM
To: olivier.dugeon@orange.com<mailto:olivier.dugeon@orange.com>; Dhruv Dhody <dhruv.ietf@gmail.com><mailto:dhruv.ietf@gmail.com>
Cc: pce@ietf.org<mailto:pce@ietf.org>
Subject: Re: [Pce] Implementation option of draft-ietf-pce-stateful-interdomain-01.txt

Hi Olivier,

Thanks for pointing this out. I think the presentation slide wording might have been a bit stronger than what is currently written in the posted draft, as the text does not prohibit the use of RRO but rather acknowledge and document that there are implementations which skip inclusion of SR-RRO (Nokia implementation does send SR-RRO), so it documents how to handle this scenario on the PCE. The text indicates that SR-RRO may or may not be included, and if omitted the PCE is to fallback to treating the ERO “like” it was an RRO.

https://datatracker.ietf.org/doc/html/draft-koldychev-pce-operational-03#section-6

   A PCC MUST send an (possibly empty) ERO/SR-ERO/SRv6-ERO in the PCRpt
   message for every LSP.  A PCC MAY send an SR-RRO/SRv6-RRO for an SR-
   TE/SRv6-TE LSP (respectively).  A PCE SHOULD interpret the RRO/SR-
   RRO/SRv6-RRO as the actual path the LSP is taking but MAY interpret
   only the ERO/SR-ERO/SRv6-ERO as the actual path.  In the absence of
   an RRO/SR-RRO/SRv6-RRO a PCE SHOULD interpret the ERO/SR-ERO/SRv6-ERO
   (respectively) as the actual path for the LSP.

I think the potential interdomain stitching label case you point out and the S-Flag defined in RFC8664 mentioned by Dhruv during the meeting seem to be valid use cases where an SR-RRO would need to be included.

Thanks!
Andrew

From: Pce <pce-bounces@ietf.org<mailto:pce-bounces@ietf.org>> on behalf of "olivier.dugeon@orange.com<mailto:olivier.dugeon@orange.com>" <olivier.dugeon@orange.com<mailto:olivier.dugeon@orange.com>>
Organization: Orange Labs
Date: Thursday, March 11, 2021 at 5:17 AM
To: Dhruv Dhody <dhruv.ietf@gmail.com<mailto:dhruv.ietf@gmail.com>>
Cc: "pce@ietf.org<mailto:pce@ietf.org>" <pce@ietf.org<mailto:pce@ietf.org>>
Subject: Re: [Pce] Implementation option of draft-ietf-pce-stateful-interdomain-01.txt

Hello Dhruv, all,

Following the presentation done during the IETF meeting, please find the link to the presentation: https://datatracker.ietf.org/meeting/110/materials/slides-110-pce-32-inter-domain-00

I also not a major point to take into account following the presentation of draft PCEP Operational Clarification (draft-koldychev-pce-operational) see https://datatracker.ietf.org/doc/draft-koldychev-pce-operational/ and https://datatracker.ietf.org/meeting/110/materials/slides-110-pce-34-operational-clarification-00:

 => In this draft, authors propose to use SR-ERO/SRv6-ERO and to NOT use SR-RRO/SR-v6-RRO for Segment Routing.

As a consequence for the stateful inter-domain draft, proposed option d1, d2 and d3 become invalid as it uses the RRO to convey the Stiching Label. Thus, only option d4 with a specific new sub-Object to convey the Stitching Label remains valid.

As usual, comments are welcome.

Regards

Olivier
Le 26/02/2021 à 05:35, Dhruv Dhody a écrit :
Hi Olivier,

Thanks for starting this thread.

As a WG participant...

On Tue, Feb 23, 2021 at 12:05 AM <olivier.dugeon@orange.com<mailto:olivier.dugeon@orange.com>> wrote:
Dear all,

According to the remark about implementation we got during the WG call
for adoption, we would start a new thread to discuss this point.
The goal isto prepare the discussion for next IETF meeting and reach a
consensusin order to edit revision 2 of the draft.

The stitching label principle requires at least a certain number of
modifications in the current PCEP version:

 a) A new PCE Capability to announce the inter-domain behaviour
 b) A new PCE Association Group to associate the local paths identifier
    to the inter-domain identifier
 c) new PCEP Errors to manage the Stitching Label exchange
 d) A mechanism to convey the Stitching Label

If there is no other choice than to reuse existing PCEP Objects by
allocating new code points for modifications a-c,there is several
options for point d, which we have tried to list below:

 d1) Use ERO and RRO in conjunction to new Path Setup code points as
     described in version 01 of the draft. It is the simplest
     implementation but as mention by Dhruv, each time a new path
     enforcement appear, a new PST code point must be allocated.
     For example, when Segment Routing v6 will be standardized, we must
     allocate a new Stitching label PST code point for SRv6.
 d2) Use ERO and ERO in conjunction to a new flag in LSP. Simple as for d1,
     but need to use the LSP Extended Flag draft as all LSP flags have been
     already allocated.
 d3) Same as d2 but find another place for the flag e.g. SRP or LSPA Object.
 d4) Define a new PCEP sub-Objet TLV within the LSP Object to convey the
     stitching label. This is more independent but need extra parsing from
     an implementation point of view.

My preference would for d2 or d3 (in that order).
LSP Extended Flag is adopted by the WG and is ready for prime-time use -- let's use it :)
Authors of LSP Extended Flag are waiting for the draft blockade to be lifted to post the -00 WG I-D.

Thanks!
Dhruv

Please, give us your opinion about these different options and don't hesitate
to propose others.

Regards

Olivier on be-half of co-author's

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_________________________________________________________________________________________________________________________

Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc

pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler

a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration,

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they should not be distributed, used or copied without authorisation.

If you have received this email in error, please notify the sender and delete this message and its attachments.

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Thank you.
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[Orange logo]<http://www.orange.com/>

Olivier Dugeon
Orange Expert, Future Networks
Open Source Referent
Orange/IMT/OLN/WTC/IEE/iTeQ

fixe : +33 2 96 07 28 80
mobile : +33 6 82 90 37 85
olivier.dugeon@orange.com<mailto:olivier.dugeon@orange.com>

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