Re: [mpls] [spring] should draft-ietf-mpls-spring-entropy-label be published as a RFC on the standards track?

[Loa Andersson <[e-mail]>]

Eric, Stewart, wg,

Wouldn't just a few words in the draft saying something along the lines

"This document should not be interpreted in such a way that the ECMP
  behavior is limited to rely on EL only."

Go a long way to clarify Stewart's concerns?

/Loa

On 2018-05-02 16:52, Eric Gray wrote:
> Stewart, et al,
> 
>                  Loa just pointed out that I made a typo in the original 
> mail below.  In the second paragraph, I meant to say:
> 
>                  “Explicitly limiting ECMP behavior to …”
> 
> --
> 
> Eric
> 
> *From:*mpls [mailto:[e-mail]] *On Behalf Of *Eric Gray
> *Sent:* Wednesday, May 02, 2018 10:28 AM
> *To:* Stewart Bryant <[e-mail]>; Andrew G. Malis 
> <[e-mail]>; Loa Andersson <[e-mail]>
> *Cc:* [e-mail]; [e-mail]; [e-mail]; 
> [e-mail]
> *Subject:* Re: [mpls] [spring] should 
> draft-ietf-mpls-spring-entropy-label be published as a RFC on the 
> standards track?
> 
> Stewart,
> 
>                  At least one view of the purpose of an Entropy label is 
> that it _/adds/_ entropy to the process of path selection.
> 
>                  Explicitly limiting EL behavior to rely exclusively on 
> use of the entropy label would also explicitly _/limit/_ the total 
> entropy to whatever the implementation that provided the entropy label 
> was implemented to treat as _/sufficient/_ among all paths in the ECMP 
> gestalt, possibly including branches that implementation might not know 
> about.
> 
>                  I doubt very much that many of the problems you refer 
> to would have arisen if folks generally felt that the entropy label – by 
> itself – provides sufficient entropy.
> 
>                  It might make sense to impose this restriction – 
> optionally – when a deployment occurs in which any particular 
> pathological behavior might be expected to occur.
> 
>                  In that case, it might be very important to ensure that 
> the limited approaches available for maximizing efficient load 
> distribution via explicit and exclusive use of the entropy label are 
> acceptable to a reasonably diverse set of implementers, as support for 
> at least one of those approaches would then become a mandatory part of 
> every standard implementation.
> 
>                  Even so, I don’t believe it is a good idea to restrict 
> implementations from using other approaches in every case.
> 
>                  The simplest example possible (where doing so is a big 
> problem) is one where the entropy labels provided have N possible 
> values  and there are M possible paths, where M>N. In any scenario where 
> this occurs, M-N paths simply will not be used.
> 
> --
> 
> Eric
> 
> *From:*mpls [mailto:[e-mail]] *On Behalf Of *Stewart Bryant
> *Sent:* Wednesday, May 02, 2018 9:52 AM
> *To:* Andrew G. Malis <[e-mail] <mailto:[e-mail]>>; 
> Loa Andersson <[e-mail] <mailto:[e-mail]>>
> *Cc:* [e-mail] <mailto:[e-mail]>; [e-mail] 
> <mailto:[e-mail]>; [e-mail] <mailto:[e-mail]>; 
> [e-mail] 
> <mailto:[e-mail]>
> *Subject:* Re: [mpls] [spring] should 
> draft-ietf-mpls-spring-entropy-label be published as a RFC on the 
> standards track?
> 
> Be careful.
> 
> There is text in the draft that talks about ECMP behaviour in different 
> parts of the path, which implies an expectation that the EL is the sole 
> source of entropy. If we make this ST then we will be implicitly 
> standardizing that behaviour. Now as it happens, I thing we need to 
> update the EL behaviour to make it the sole source of entropy, because 
> that solves a number of problems, particularly in network 
> instrumentation, but we need to do that explicitly and not as an 
> artefact of this draft.
> 
> So the way I see it, either this draft is published as informational, or 
> it is published as ST without any text that implies that the EL is the 
> sole source of entropy, or we harden the EL behaviour (which I think we 
> need to do) and this draft is published with a normative reference to an 
> RFC that specifies the stricter EL behaviour.
> 
> - Stewart
> 
> On 02/05/2018 14:01, Andrew G. Malis wrote:
> 
>     Loa,
> 
>     There’s plenty of RFC 2119 language in the draft, so I support
>     making this standards track.
> 
>     Cheers,
> 
>     Andy
> 
>     On Wed, May 2, 2018 at 3:44 AM, Loa Andersson <[e-mail]
>     <mailto:[e-mail]>> wrote:
> 
>         Working Group,
> 
>         February 1st the MPLS working Group requested that draft-ietf-mpls-
>         spring-entropy-label should be published as an Informational RFC.
> 
>         During the RTG Directorate and AD reviews the question whether the
>         document should instead be published as a RFC on the Standards Track
>         has been raised.
> 
>         The decision to make the document Informational was taken "a
>         long time
>         ago", based on discussions between the authors and involving the
>         document shepherd, on the wg mailing list. At that point it we were
>         convinced that the document should be progressed as an Informational
>         document.
> 
>         It turns out that there has been such changes to the document
>         that we
>         now would like to request input from the working group if we
>         should make
>         the document a Standards Track RFC.
> 
>         Daniele's RTG Directorate review can be found at at:
>         https://datatracker.ietf.org/doc/review-ietf-mpls-spring-entropy-label-08-rtgdir-lc-ceccarelli-2018-02-21/
> 
>         All the issues, with the exception whether it should be
>         Informational
>         or Standards track, has been resolved as part AD review.
> 
>         If the document is progressed as a Standard Tracks document then we
>         also need to answer the question whether this is an update RFC 6790.
> 
>         This mail starts a one week poll (ending May 9) to see if we have
>         support to make the document a Standards Track document. If you
>         support
>         placing it on the Standards Track also consider if it is an
>         update to
>         RFC 6790.
> 
>         Please send your comments to the MPLS wg mailing list (
>         [e-mail] <mailto:[e-mail]> ).
> 
>         /Loa
>         for the mpls wf co-chairs
> 
>         PS
> 
>         I'm copying the spring working group on this mail.
>         -- 
> 
> 
>         Loa Andersson                        email: [e-mail]
>         <mailto:[e-mail]>
>         Senior MPLS Expert
>         Bronze Dragon Consulting             phone: [phone]
> 
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-- 


Loa Andersson                        email: [e-mail]
Senior MPLS Expert
Bronze Dragon Consulting             phone: [phone]