Re: [mpls] Concerns about ISD

Tianran Zhou <zhoutianran@huawei.com> Sat, 07 May 2022 07:16 UTC

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From: Tianran Zhou <zhoutianran@huawei.com>
To: John E Drake <jdrake@juniper.net>
CC: John E Drake <jdrake=40juniper.net@dmarc.ietf.org>, Tony Li <tony.li@tony.li>, mpls <mpls@ietf.org>
Thread-Topic: [mpls] Concerns about ISD
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Date: Sat, 7 May 2022 07:16:06 +0000
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Subject: Re: [mpls] Concerns about ISD
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See below in line.

Tianran


[JD]  To recap this extended discussion:

1)  A is binding SID, which is optional and which makes SR label stacks smaller but not necessarily small

2)  B is NAS.

3)  Even with A, SR label stacks may be large

[ZTR] So, on the other hand, BSID could apply and make the stack smaller.

4)  Because of 3),  a transit node may not be able to find the bottom of stack

[ZTR] Maybe, but we need use cases and operators back to confirm this requirement. If we indeed need the extreme effect, I would prefer Robert’s RAF proposal.

5)  Because of 4), there need to be multiple copies of a NAS within a stack

[ZTR] We need analysis on the specific proposal and comparison on: how it works, how it is better, what side effects are introduced, etc. So this point is not an easy conclusion.

6)  A network action may have ancillary data and that ancillary data may be in-stack or post-stack

7)  Because of 4), a network action related to forwarding which has ancillary data should specify that it is in-stack

[ZTR] Before we do this, use case is necessary. We do not want to build a tool without usage.

Tianran

From: John E Drake [mailto:jdrake@juniper.net]
Sent: Thursday, May 5, 2022 9:02 PM
To: Tianran Zhou <zhoutianran@huawei.com<mailto:zhoutianran@huawei.com>>
Cc: John E Drake <jdrake=40juniper.net@dmarc.ietf.org<mailto:jdrake=40juniper.net@dmarc.ietf.org>>; Tony Li <tony.li@tony.li<mailto:tony.li@tony.li>>; mpls <mpls@ietf.org<mailto:mpls@ietf.org>>
Subject: RE: [mpls] Concerns about ISD

BSID and NAS are for completely different purposes.  The former is for stack compression and the latter is for network actions.

Yours Irrespectively,

John



Juniper Business Use Only
From: Tianran Zhou <zhoutianran@huawei.com<mailto:zhoutianran@huawei.com>>
Sent: Wednesday, May 4, 2022 8:43 PM
To: John E Drake <jdrake@juniper.net<mailto:jdrake@juniper.net>>
Cc: John E Drake <jdrake=40juniper.net@dmarc.ietf.org<mailto:jdrake=40juniper.net@dmarc.ietf.org>>; Tony Li <tony.li@tony.li<mailto:tony.li@tony.li>>; mpls <mpls@ietf.org<mailto:mpls@ietf.org>>
Subject: RE: [mpls] Concerns about ISD

[External Email. Be cautious of content]

Hi,
It does not make sense to me to create a new mechanism as ISD in operators’ network, while not using existing mature BSID.
There is no sign the reinvented wheel could be better.

Tianran

From: John E Drake [mailto:jdrake@juniper.net]
Sent: Saturday, April 30, 2022 12:05 AM
To: Tianran Zhou <zhoutianran@huawei.com<mailto:zhoutianran@huawei.com>>
Cc: John E Drake <jdrake=40juniper.net@dmarc.ietf.org<mailto:jdrake=40juniper.net@dmarc.ietf.org>>; Tony Li <tony.li@tony.li<mailto:tony.li@tony.li>>; mpls <mpls@ietf.org<mailto:mpls@ietf.org>>
Subject: Re: [mpls] Concerns about ISD

Comment inline
Sent from my iPhone

On Apr 29, 2022, at 11:17 AM, Tianran Zhou <zhoutianran@huawei.com<mailto:zhoutianran@huawei.com>> wrote:

[External Email. Be cautious of content]

Hi,
Comments inline.

Tianran

>
> Hi John,
>
>  If we want to reuse this for consistent design (easy for interop), how do you
> want to encode it to ISD?
>
> [JD]  That's up to a given solution to propose, but probably two LSEs
>
> ZTR> It would be interesting to know your proposal.

[JD]  As I said, the size of an NRP ID needs to be decided and any MNA solution needs propose how it is to be
encoded

ZTR> Ok, so any solution need to demonstrate how it works.

>
>
> 2. If we really worry about the MSD of SR, why not use BSID as a direct way to
> reduce the stack?
>
> [JD]  Because it can't be mandated
>
> ZTR> I am sorry, I do not understand why BSID is not applicable. What's the "
> mandated " mean here?

[JD]  MNA cannot require the use of BSIDs

ZTR> Is this an agreed requirement? In the requirement draft? I still can’t understand. On one hand, you worry about low stack depth. On the other hand, you don’t want to use an easy way to solve this problem.
[JD]  I don’t think it’s realistic to tell a network operator that they have to deploy BSID in order to deploy MNA.  Also, I don’t think it’s a good solution became a label stack of BSIDs may still be too large and the node advertising the BSID is going to expand the the label stack with the path SIDS so the nodes on the path will have to deal with a large label stack.


>
> Tianran