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

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

Hi Gyan,

Gyan2> What is the advantage of using TEA encoding as opposed to existing PTA RFC 6513 & RFC 6514 MVPN signaling?

This is about using procedures in draft-ietf-bess-bgp-multicast-controller to set up (s,g) forwarding state in a VRF, as an alternative to BGP-MVPN.

As described in https://datatracker.ietf.org/doc/html/draft-ietf-bess-bgp-multicast-controller-09#section-2, instead of ingress/egress PE figuring out the (s,g) state based on BGP-MVPN signaling and PIM signaling (for local OIFs to CEs), they simply take instructions from a control on what tunnel branches and which local OIFs to use – as if an operator is configuring them statically. This allows the PEs to be very dumb and simple.

From that point of view, there is no difference between “underlay” and “overlay” and the TEA is perfect to encode that information – each “tunnel” in the TEA is a replication branch.

That section does have the following that makes use of the PTA (attached to MCAST-TREE NLRIs for programing VRF (s,g) forwarding state):

   The Replication State route may also have a PMSI Tunnel Attribute
   (PTA) attached to specify the provider tunnel while the TEA specifies
   the local PE-CE interfaces where traffic need to be sent out.  This
   not only allows provider tunnel without a binding SID (e.g., in a
   non-SR network) to be specified without explicitly listing its
   replication branches, but also allows the service controller for MVPN
   overlay state to be independent of provider tunnel setup (which could
   be from a different transport controller or even without a
   controller).

Jeffrey



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From: Gyan Mishra <[e-mail]>
Sent: Thursday, April 28, 2022 12:19 AM
To: Jeffrey (Zhaohui) Zhang <[e-mail]>
Cc: BESS <[e-mail]>; Bidgoli, Hooman (Nokia - CA/Ottawa) <[e-mail]>; Susan Hares <[e-mail]>; [e-mail]; [e-mail]
Subject: Re: [bess] [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

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Hi Jeffrey

Please see Gyan2>

On Tue, Apr 12, 2022 at 11:02 AM Jeffrey (Zhaohui) Zhang <[e-mail]<mailto:[e-mail]>> wrote:
Hi Gyan,

Please see zzh2> below.



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From: Gyan Mishra <[e-mail]<mailto:[e-mail]>>
Sent: Friday, April 8, 2022 8:48 PM
To: Jeffrey (Zhaohui) Zhang <[e-mail]<mailto:[e-mail]>>
Cc: BESS <[e-mail]<mailto:[e-mail]>>; Bidgoli, Hooman (Nokia - CA/Ottawa) <[e-mail]<mailto:[e-mail]>>; Susan Hares <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Re: [bess] [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

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Hi Jeffrey

Please see Gyan>


On Tue, Apr 5, 2022 at 7:38 PM Jeffrey (Zhaohui) Zhang <[e-mail]<mailto:[e-mail]>> wrote:
Hi Gyan,

Please see zzh> below for my view.



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From: Gyan Mishra <[e-mail]<mailto:[e-mail]>>
Sent: Tuesday, March 29, 2022 10:31 AM
To: Jeffrey (Zhaohui) Zhang <[e-mail]<mailto:[e-mail]>>
Cc: BESS <[e-mail]<mailto:[e-mail]>>; Bidgoli, Hooman (Nokia - CA/Ottawa) <[e-mail]<mailto:[e-mail]>>; Susan Hares <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Re: [bess] [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

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Dear authors

Can you describe in more detail the relationship and interaction between the two SR P2MP variants below:

Defines new SAFI for SR P2MP variant
https://datatracker.ietf.org/doc/html/draft-hb-idr-sr-p2mp-policy-04<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-hb-idr-sr-p2mp-policy-04__;!!NEt6yMaO-gk!RNg1gSHc7bgU2dou9enCSiVF-PXIWQ2Wk4mTxBBHjYxjFPb_mdHB9D5C3jKh83Sr$>

zzh> draft-ietf-bess-bgp-multicast-controller (referred to as draft-bess) defines a SAFI and different route types of that SAFI to setup replication state on IP/mLDP/SR-P2MP tree nodes. One of the route types is for SR-P2MP purposes.
Zzh2> Correction – the MCAST-TREE SAFI is defined in draft-ietf-bess-bgp-multicast.

   Gyan> Ack
Zzh> draft-hb-idr-sr-p2mp-policy (draft in this adoption call, referred to as draft-hb) defines a different SAFI and route types for the same SR-P2MP purposes.
 Gyan> The adoption call draft is aligned with SR-TE policy as P2MP extension for simplicity for operators which I agree makes sense.
Does this draft utilize all the drafts below Tree sid / Replication sid and SR P2MP MVPN procedures for auto discovery etc.

Zzh> Both drafts are for realizing the two tree-sid drafts mentioned below; both can be used for draft-ietf-bess-mvpn-evpn-sr-p2mp.
 Gyan> Ack
Zzh> As I mentioned before, both draft-bess and draft-hb have its own considerations. The biggest difference is how the replication information is encoded in the Tunnel Encapsulation Attribute (TEA).

Gyan> Ack
Zzh> I can understand that the IDR/PIM/BESS WGs may decide to accept both ways of encoding replication information in the TEA, but I believe we should share SAFI and route types between the two drafts – only the TEA would be different.

Gyan> Both the BESS and IDR adoption draft are vastly different solutions that have very different goals I don’t see any reason or need to have similarities as far as TEA or SAFI encodings or usage.  The BGP controller draft has a very wide scope, but also is more of an alternative approach as it introduces new extensibility idea of utilizing TEA and wide communities encoding to make the solution RFC 6513 and 6514 MVPN signaling independent.  That is a drastic change for scalability for operations traditional use of multicast X-PMSI P-Tree  leveraging the separation of control plane from forwarding plane with RR using traditional MVPN procedures.  As the ideas from the BESS draft as it builds on the BGP Multicast draft is to eliminate soft state tree building protocols and with the move towards hard state, thus the signaling paradigm change from traditional MVPM procedures to alternate TEA and wide community encoding.  Am I reading that correctly as the goals of the BESS draft?

Zzh2> Not really 😊
 Gyan> Ok
The BESS document also mentions that the solution can be used for underlay and overlay trees as replacement for MVPN signaling.  For underlay trees are you referring to GTM?  I have many more questions about the BESS draft and will ask in a new thread.

Zzh2> draft-ietf-bess-bgp-multicast-controller was initially intended to build traditional IP multicast trees (w/o any VPN specifics) and mLDP tunnels (started in September 2017) with calculation on and signaling from controllers. SR-P2MP was added in -03 (July 2020) because the generic mechanism for IP/mLDP trees can be used for SR-P2MP as well. These can all be considered as underlay.
    Gyan> Ack
Zzh2> Overlay support – as an MVPN replacement – was added in -06 (February 2021), but the concept is *not different* from underlay at all – we’re just setting up (s, g) IP multicast state in VRFs, with downstream nodes including remote VRFs connected by some sort of tunnels. That is not different from setting up state in global table at all.

     Gyan2> Ack

   Gyan2> What is the advantage of using TEA encoding as opposed to existing PTA RFC 6513 & RFC 6514 MVPN signaling?
Zzh2> Thanks.
Zzh2> Jeffrey
Zzh> Jeffrey

Defines Tree SID stitching of replication SID SR policy P2MP variant
https://datatracker.ietf.org/doc/html/draft-voyer-pim-sr-p2mp-policy-00<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-voyer-pim-sr-p2mp-policy-00__;!!NEt6yMaO-gk!RNg1gSHc7bgU2dou9enCSiVF-PXIWQ2Wk4mTxBBHjYxjFPb_mdHB9D5C3gdi0hAB$>

Replication SID
https://datatracker.ietf.org/doc/html/draft-ietf-spring-sr-replication-segment<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-ietf-spring-sr-replication-segment__;!!NEt6yMaO-gk!RNg1gSHc7bgU2dou9enCSiVF-PXIWQ2Wk4mTxBBHjYxjFPb_mdHB9D5C3smIMNzh$>

Defines new SR P2MP PTA using MVPN procedures
https://datatracker.ietf.org/doc/html/draft-ietf-bess-mvpn-evpn-sr-p2mp<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-ietf-bess-mvpn-evpn-sr-p2mp__;!!NEt6yMaO-gk!RNg1gSHc7bgU2dou9enCSiVF-PXIWQ2Wk4mTxBBHjYxjFPb_mdHB9D5C3g-W3jH0$>


Kind Regards

Gyan


On Mon, Mar 28, 2022 at 3:39 PM Jeffrey (Zhaohui) Zhang <zzhang=[e-mail]<mailto:[e-mail]>> wrote:
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]<mailto:[e-mail]>>
Sent: Friday, March 25, 2022 11:34 AM
To: Jeffrey (Zhaohui) Zhang <[e-mail]<mailto:[e-mail]>>; Susan Hares <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Cc: '[e-mail]<mailto:[e-mail]>' <[e-mail]<mailto:[e-mail]>>; 'BESS' <[e-mail]<mailto:[e-mail]>>
Subject: RE: [Idr] draft-hb-idr-sr-p2mp-policy (3/10 to 3/24/2022) - Adoption call

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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]<mailto:[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

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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

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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
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Gyan Mishra

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M 301 502-1347

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Gyan Mishra

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Gyan Mishra

Network Solutions Architect

Email [e-mail]<mailto:[e-mail]>

M 301 502-1347