Re: [Detnet] [mpls] [Pals] draft-decraene-mpls-slid-encoded-entropy-label-id (was RE: Please review the PALS/MPLS/DetNet Joint Session minutes)

John,

I understand that there may be different ways to create network slices, so may be some additional context may be useful.
draft-decraene-mpls-slid-encoded-entropy-label-id is proposing a way to encode the slice ID which is needed for some approaches e.g. the “Global Identifier Based Selector” from https://datatracker.ietf.org/doc/html/draft-bestbar-teas-ns-packet#section-5.1.1
In short, the top label is defining the routing hence the (set of) outgoing interfaces on a given LSR. This routing is not altered by the slice ID.

Clearly, the “controller” defining the slice, need to enforce a route (hence the set of next-hops) which is compatible with the slice (ID) characteristics. This point would probably be better discussed as part of draft-bestbar-teas-ns-packet or more generally in the TEAS WG.
draft-decraene-mpls-slid-encoded-entropy-label-id is only providing a way to encode the slice ID in the MPLS packet.

--Bruno

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From: John E Drake <jdrake@juniper.net>
Sent: Wednesday, March 30, 2022 10:03 PM
To: Henderickx, Wim (Nokia - BE/Antwerp) <wim.henderickx@nokia.com>; DECRAENE Bruno INNOV/NET <bruno.decraene@orange.com>
Cc: mpls <mpls@ietf.org>; detnet WG <detnet@ietf.org>; pals@ietf.org
Subject: RE: [mpls] [Pals] draft-decraene-mpls-slid-encoded-entropy-label-id (was RE: Please review the PALS/MPLS/DetNet Joint Session minutes)

Wim,

I think I would term it a thought experiment.  An RFC 6790 compliant node will take the value in the EL label field and use it to select an outgoing interface.  If the value in the EL field is a slice ID, such an node will select an outgoing interface which is not necessarily part of the slice in question and that outgoing interface will be to a node which is not necessarily part of the slice in question.

Yours Irrespectively,

John

Juniper Business Use Only
From: Henderickx, Wim (Nokia - BE/Antwerp) <wim.henderickx@nokia.com<mailto:wim.henderickx@nokia.com>>
Sent: Wednesday, March 30, 2022 3:21 PM
To: John E Drake <jdrake@juniper.net<mailto:jdrake@juniper.net>>; bruno.decraene@orange.com<mailto:bruno.decraene@orange.com>
Cc: mpls <mpls@ietf.org<mailto:mpls@ietf.org>>; detnet WG <detnet@ietf.org<mailto:detnet@ietf.org>>; pals@ietf.org<mailto:pals@ietf.org>
Subject: Re: [mpls] [Pals] draft-decraene-mpls-slid-encoded-entropy-label-id (was RE: Please review the PALS/MPLS/DetNet Joint Session minutes)

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John, do you have evidence of this or is this a theoretical claim ?

From: mpls <mpls-bounces@ietf.org<mailto:mpls-bounces@ietf.org>> on behalf of John E Drake <jdrake=40juniper.net@dmarc.ietf.org<mailto:jdrake=40juniper.net@dmarc.ietf.org>>
Date: Wednesday, 30 March 2022 at 19:13
To: bruno.decraene@orange.com<mailto:bruno.decraene@orange.com> <bruno.decraene@orange.com<mailto:bruno.decraene@orange.com>>
Cc: mpls <mpls@ietf.org<mailto:mpls@ietf.org>>, detnet WG <detnet@ietf.org<mailto:detnet@ietf.org>>, pals@ietf.org<mailto:pals@ietf.org> <pals@ietf.org<mailto:pals@ietf.org>>
Subject: Re: [mpls] [Pals] draft-decraene-mpls-slid-encoded-entropy-label-id (was RE: Please review the PALS/MPLS/DetNet Joint Session minutes)
Except that putting a slice ID in the Entropy Label field will break existing  ELI/EL Implementations because their hashing of the slice ID won’t necessarily place a packet on the correct outgoing I/F
Sent from my iPhone

On Mar 30, 2022, at 1:00 PM, bruno.decraene@orange.com<mailto:bruno.decraene@orange.com> wrote:

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From: Tony Li <tony1athome@gmail.com<mailto:tony1athome@gmail.com>> On Behalf Of Tony Li
Sent: Wednesday, March 30, 2022 4:08 PM
> [Kireeti]: suggest attending talk by Tony on danger of reusing ELI before making any decision.
https://notes.ietf.org/notes-ietf-113-pals<https://urldefense.com/v3/__https:/notes.ietf.org/notes-ietf-113-pals__;!!NEt6yMaO-gk!Sw9ofU9AyD7Z-JKwyAqMlHk5xhNLxZNMSu31Yt6-K7yh-6JehvlSPLDcqrP3gOo$>

Done. The talk raised no “danger of reusing ELI” for draft draft-decraene-mpls-slid-encoded-entropy-label-id; quite the contrary.
I quote: “claims of backward compatibility apply to draft-decraene-mpls-slid-encoded-entropy-label-id-03”. With more details on slide 18
https://datatracker.ietf.org/meeting/113/materials/slides-113-mpls-05-policy-on-mpls-special-purpose-labels-reuse-00<https://urldefense.com/v3/__https:/datatracker.ietf.org/meeting/113/materials/slides-113-mpls-05-policy-on-mpls-special-purpose-labels-reuse-00__;!!NEt6yMaO-gk!Sw9ofU9AyD7Z-JKwyAqMlHk5xhNLxZNMSu31Yt6-K7yh-6JehvlSPLDcNEC7QKk$>

Yes, the issue with this proposal is that it has no space for in-stack data and not enough space for possible expansion of additional actions.

[Bruno] There are two steps:
- This proposal allows for carrying 8 Indicators and a slice ID while been backward compatible with egress LER hance providing faster deployment with incremental benefit.
- If more in-stack data is required the proposal is extensible (e.g. draft-jags-mpls-ext-hdr) but at the cost of losing the above benefits for the ASes & uses-cases requiring more than 8 Indicators per AS or In-Stack Data.
So we can have both worlds: simple first step and extensibility for those who need it.

Independently, we also/already have the post stack data option to carry ancillary data, which may limit the need for In-Stack data extension.

--Bruno

Tony

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