Re: [pim] [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

["Jeffrey (Zhaohui) Zhang" <[e-mail]>]

Hi,

When it comes to SR-P2MP state downloading, there are three aspects involved here:


  1.  NLRI to encode policy information
  2.  NLRI to encode <tree/path/instance, node> identification
  3.  Tunnel Encapsulation Attribute (TEA) that encodes actual replication branches

The major difference between the two ways is on #3. Indeed, we could not reach consensus - there are two ways of encoding the TEA and each has its own considerations. The draft-ietf-bess way (even when used for SR-P2MP) is aligned with other non-SR multicast trees (IP/mLDP) for a unified approach, while draft-hb is aligned to unicast BGP SR policy.

I want to initiate a discussion and I can understand that WGs may eventually choose to allow both ways for #3. Even so, I think we should strive for consistent approach at least for #1 and #2 (and for that I am not saying that draft-ietf-bess way must be used). For example, use the same SAFI and route types for both ways, but use different TEA encoding methods.

Thanks.

Jeffrey



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From: Bidgoli, Hooman (Nokia - CA/Ottawa) <[e-mail]>
Sent: Friday, March 25, 2022 11:34 AM
To: Jeffrey (Zhaohui) Zhang <[e-mail]>; Susan Hares <[e-mail]>; [e-mail]
Cc: '[e-mail]' <[e-mail]>; 'BESS' <[e-mail]>
Subject: RE: [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

[External Email. Be cautious of content]

Hi All

Zzh> I do think BGP signaling for SR P2MP is appropriate. We just need to discuss the two ways and figure out how to proceed. The authors have discussed before though we have not reached consensus.

HB> yes there was discussion and there was no consensus to merge the 2 drafts as their approach is widely different. The authors of this draft have kept the implementation very close to unicast BGP SR Policy for the segment list, which simplifies the implementation and deployment of the technology. As you said there seems to be two way to download this policy and the segment list and we can work on both.
Given the solid support I don't see why the adoption of this draft should  be delayed because of these arguments.

Thanks
Hooman

From: pim <[e-mail]<mailto:[e-mail]>> On Behalf Of Jeffrey (Zhaohui) Zhang
Sent: Friday, March 25, 2022 10:47 AM
To: Susan Hares <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Cc: '[e-mail]' <[e-mail]<mailto:[e-mail]>>; 'BESS' <[e-mail]<mailto:[e-mail]>>
Subject: Re: [pim] [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

[+ BESS, PIM]

Hi,

I realized that in a hurry I did not respond to the specific questions below. Please see zzh> next to the questions.

Looks like that there are some comments on BESS/PIM list and I will go through those to see if I have any addition/follow-up on those.



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From: Idr <[e-mail]<mailto:[e-mail]>> On Behalf Of Jeffrey (Zhaohui) Zhang
Sent: Friday, March 25, 2022 6:30 AM
To: Susan Hares <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Subject: Re: [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

[External Email. Be cautious of content]

I am sorry for responding late. I somehow missed this.

I think we should discuss the relationship with daft-ietf-bess-bgp-multicast-controller further before adopting this.

Thanks.
Jeffrey



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From: Idr <[e-mail]<mailto:[e-mail]>> On Behalf Of Susan Hares
Sent: Thursday, March 10, 2022 10:28 AM
To: [e-mail]<mailto:[e-mail]>
Subject: Re: [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

[External Email. Be cautious of content]

IDR WG:

If you just wish to respond to the IDR list,
you may respond to this email on the adoption call.

Cheers, Sue

From: Idr [mailto:[e-mail]] On Behalf Of Susan Hares
Sent: Thursday, March 10, 2022 9:55 AM
To: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022)

This begins a 2 week WG adoption call for:
draft-hb-idr-sr-p2mp-policy from (3/10 to 3/24/2022)

You can obtain the draft at:
https://datatracker.ietf.org/doc/draft-hb-idr-sr-p2mp-policy/<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-hb-idr-sr-p2mp-policy/__;!!NEt6yMaO-gk!TfiPI1NfecN3db3pj6WZ8paxUr4s6OvmVZ91mapddPFeCkFZJodxFk8aTGCpYg34$>

In your comments for this call please consider:

Zzh> I want to point out that https://datatracker.ietf.org/doc/draft-ietf-bess-bgp-multicast-controller/<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-ietf-bess-bgp-multicast-controller/__;!!NEt6yMaO-gk!S33KKHGKJVywLaE5hTpBZvb2Og_8GrdduTTT-6xmknLUl8Yylk7RNo3lGazDpUZk$> is another way to do the same. I also explained in https://mailarchive.ietf.org/arch/msg/idr/KObeSgKPu3HRbd0ZN7L7fWq_Eto/<https://urldefense.com/v3/__https:/mailarchive.ietf.org/arch/msg/idr/KObeSgKPu3HRbd0ZN7L7fWq_Eto/__;!!NEt6yMaO-gk!S33KKHGKJVywLaE5hTpBZvb2Og_8GrdduTTT-6xmknLUl8Yylk7RNo3lGW1pXg_c$> why it was in the bess WG.
Zzh> In addition, the bess draft supports *other* multicast trees (IP, mLDP besides SR-P2MP) using a consistent way.

1)  Does this technology support the SR P2MP features
that distributes candidate paths which connect
a multicast distribution tree (tree to leaves).

Zzh> It is one way to use BGP to support that. The bess draft specifies another way.

2) Is the technology correctly specified for the
NLRI (AFI/SAFI) and the tunnel encapsulation attribute
additions (sections 2 and 3)?

Zzh> The specified SAFI and tunnel encapsulation attribute additions are one way for the BGP signaling for SR-P2MP. The bess draft specifies another way.

3) Does the P2MP policy operation (section 4)
provide enough information for those implementing this
technology and those deploying the technology?

4) Do you think this multicast technology is a good
Place to start for P2MP policy advertisement via BGP?

Zzh> Both ways are good place to start. We just need to figure out how to proceed with the two proposals.

5) Do you think this SR P2MP policies should not be advertised
via BGP?

Zzh> I do think BGP signaling for SR P2MP is appropriate. We just need to discuss the two ways and figure out how to proceed. The authors have discussed before though we have not reached consensus.
Zzh> Thanks!
Zzh> Jeffrey

Cheers, Susan Hares