Re: [Pce] draft-hsd-pce-sr-p2mp-policy wiki comments and action.

["Bidgoli, Hooman (Nokia - CA/Ottawa)" <[e-mail]>]

Hi Dhruv

Much appreciate your reply, Inline

Thanks
Hooman


-----Original Message-----
From: Dhruv Dhody <[e-mail]> 
Sent: Tuesday, February 9, 2021 5:28 AM
To: Bidgoli, Hooman (Nokia - CA/Ottawa) <[e-mail]>
Cc: [e-mail]; [e-mail]
Subject: Re: draft-hsd-pce-sr-p2mp-policy wiki comments and action.

Hi Hooman,

Apologies! Missed replying to this email...

On Fri, Jan 22, 2021 at 12:27 AM Bidgoli, Hooman (Nokia - CA/Ottawa) <[e-mail]> wrote:
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> Dear Chairs
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> Looking at the wiki page there was a comment on the sr-p2mp-policy draft.
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> draft-hsd-pce-sr-p2mp-policy
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> 109; More work is needed - align to PCECC, text needs to aligned to 
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> The authors took an action to setup a meeting and discuss the alignment with PCECC farther. The final outcome of this meeting was unanimous agreement, by all the authors/vendors on the draft, to go forward with ERO object.
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As an individual I-D, it is up to the co-authors to decide the content of the I-D.

The comment (and earlier discussions) was to make sure we maintain consistency across all our documents that we produce. RFC 8283 describes the PCECC architecture, where the PCE needs to interact with not only the head-end routers (the usual stateful/stateless PCE case) but also with the egress and the internal P routers. The WG has just sent the first PCECC extension for MPLS label allocation along the path to the IESG. For other use cases such as SR/SRv6 SID allocation as well as for the branch node in the P2MP LSP and Native-IP, all are under the PCECC umbrella. So far all use cases where the PCE needs to interact with other nodes beyond the ingress and provide instructions to them are using PCECC architecture.

So when the PCE is interacting with the head end for SR P2MP Policy, it can use the usual stateful PCE extensions but when the PCE is interacting with the branch nodes and leaf nodes for replication segment, we strongly feel it should be described under the PCECC architecture. So you could use the ERO object for encoding the full P2MP path (and SR P2MP Policy) when interacting with the root node.
But when interacting with other nodes, use the PCECC technique i.e. a new CCI object type (which could be used with the ERO if needed). This would help you to not reinvent things as well as maintain consistency.
To reconfirm, the PCECC comment is related to section 3.3.3 & 4.5 only and not the whole document. If you still disagree please list the technical reason why so that the WG can evaluate them.

HB> As I am sure you do appreciate there are many ways to skin the cat. TreeSID can be connected via unicast SR path and not every node needs to be programmed. In addition as explained the PCECC did not provide the with flexibility to configure backup/fast reroute paths and the current methods does provide that capability. 
Again as mentioned we looked at PCECC very hard and tried to implement treeSID via this method but there were major short comings for backup and FRR paths.
There are multiple implementation in the field that is using the ERO object for treeSID with success.
Are the chairs suggesting that the working group is only dictating PCECC and is not open to any other option but PCECC for the purpose of programming the PCC and multicast? 
We have been asking for adaptation since 3 IETF ago and we keep getting pushback because our implementation does not follow the PCECC, why is PCECC the only choice on the table? Why isn't the working group open to other options to solve the multicast requirements? Given the fact that the ERO has been implemented and is in the field and in multiple providers labs being tested with successful outcome, I think the WG should have a open view to this implantation. Especially when multiple vendors and providers (Cisco, Juniper, Nokia, Ciena, Bell Canada) to name a few have agreed to this implementation. 


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> The authors feel ERO object in addition to draft-koldychev-pce-multipath-04 - PCEP Extensions for Signaling Multipath Information (ietf.org) for backup paths is the easiest and the most efficient way to address the programming of a replication segment on PCC from to the PCE.
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> The authors would like to move forward with the adaptation call please. In addition the authors are open to discuss the ERO preference in an interim open session with the chairs.
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The document has not been updated after 109, last we discussed this, we found that the document needed more work because it does not follow the way the PCEP extensions are usually defined. It follows a very unusual format (e.g. section 5) at places. It is good to provide examples but suggest it be done in a way that is more readable. Please follow the RBNF notations when specifying PCEP message changes (in a backward-compatible way). Some of your co-authors have vast experience in writing documents in this WG, I suggest taking their help. Hopefully, a more readable version will help you get more reviews.

HB> sure this is cosmetics and we will follow the WG suggestion, that said this should not stop the adaptation call. The sooner we have adaptation call the sooner we can have input.

HB> to close, as you mentioned some of the co-authors have vast experience in PCE WG and the same co-authors have agreed and recommended ERO implementation. As such I ask the chairs for adaptation call again ASAP. We will fix the cosmetics to be inline with WG recommendations asap.

Hope this helps, and again accept our apologies for missing replying to this email earlier.

Thanks!
Dhruv & Julien

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> Regards
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> Hooman
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