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

[Susan Hares <[e-mail]>]

Jeffrey and Hooman: 

 

This adoption call runs until 4/8/2022.  The reason I have extended the 

adoption call is to determine what interaction there is between 

draft-hb-idr-sr-p2mp-policy-04.txt (which has interest in IDR) and 

draft-ietf-bess-bgp-multicast-controller-07.txt (adopted by BESS).  

 

I need your input on these questions in order to advise BESS, PIM, and IDR 

WG-chairs + WGS on the status of these drafts.   Please let me know if I am 

Unclear on my questions. 

 

This is the first of 3 lengthy technical messages.   

 

You indicated in 

https://mailarchive.ietf.org/arch/msg/idr/8k4Pkcg0aqIwPFbSULXepsaHDSw/

 

"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 draft-ietf-bess-(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."

 

This post examines the TEA attribute discussion in section 3.1 of 

draft-ietf-bess-bgp-multicast-controller-07.txt draft. 

Section 3.1 specifies  two types of tunnels for TEA (RFC9012):

any encapsulation (3.1.1) and load balancing (3.1.2) 

plus interactions with PMSI (section 3.1.3), and 

4 Sub-TLVs.  In section 3.4.3 you provide signaling for the 

Policy to enter this tree, but you do not indicate how the 

two different tunnel types interact with

the tunnel types defined in draft-ietf-idr-segment-routing-te-policy-15.txt 

 

Section 2.4.4 of draft-ietf-idr-segment-routing-te-policy-15.txt

contains a new tunnel type: SR Policy and two groups of 

subTLVs: weight SubTLV and segment SubTLVS (A-K). 

 

1) how do the 3 Tunnel types interact? 

(all encapsulation, load balancing, and SR Policy type)

 

Please include in your discussion where this interaction is 

Described in the text. 

 

2)  How do these 3 tunnel types interact with the 

PMSI tunnels or Source-Active AD routes (types 1-3),

or ASM SPT (type 5) or C-multicast overlays (Type 6-7)? 

This is  (section 3.1.3)?  

 

3) draft-bess-bgp-multicast-controller states in section 1.7

on sr-p2mp: 

"An SR- Point-to-Multipoint (SR P2MP) policy is used to 

Define and instantiate a P2MP tree which is computed by a 

Controller." 

 

Section 3.4.2 defines the SR P2MP policy as  BGP 

Community container in the BGP Wide communities which 

Contains candidate path preference + TLVS.  

You state in section 3.4.2 

"The replicate state route for replication segments signaled to the 

root is also used to signal (parts of) the SR P2MP Policy - 

the policy name, the set of leaves [..optional], the preference of CP

and other information". 

 

3a) Are you proposing translating this from the SR Policy or what? 

3b) how are the atoms used in the policy? 

 

4) Give an example of how a simple scenario might be implemented

With section 3.4.3.1 and 3.4.3.2? 

 

 

Thank you, Sue 

 

 

From: Jeffrey (Zhaohui) Zhang [mailto:[e-mail]] 
Sent: Friday, March 25, 2022 10:47 AM
To: Susan Hares; [e-mail]
Cc: 'BESS'; '[e-mail]'
Subject: RE: [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.

 

 

Juniper Business Use Only

From: Idr <[e-mail]> On Behalf Of Jeffrey (Zhaohui) Zhang
Sent: Friday, March 25, 2022 6:30 AM
To: Susan Hares <[e-mail]>; [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

 

 

Juniper Business Use Only

From: Idr <[e-mail]> On Behalf Of Susan Hares
Sent: Thursday, March 10, 2022 10:28 AM
To: [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]; [e-mail]; [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!TfiPI1NfecN3db3pj6WZ8paxUr4s6OvmVZ91mapddPFeCk
FZJodxFk8aTGCpYg34$> 

 

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/
is another way to do the same. I also explained in
https://mailarchive.ietf.org/arch/msg/idr/KObeSgKPu3HRbd0ZN7L7fWq_Eto/ 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