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:[email protected]] On Behalf Of Eric Gray
Sent: Wednesday, May 02, 2018 10:28 AM
To: Stewart Bryant <[email protected]>; Andrew G. Malis
<[email protected]>; Loa Andersson <[email protected]>
Cc: [email protected]; [email protected]; [email protected];
[email protected]
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:[email protected]] On Behalf Of Stewart Bryant
Sent: Wednesday, May 02, 2018 9:52 AM
To: Andrew G. Malis <[email protected]<mailto:[email protected]>>; Loa
Andersson <[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>;
[email protected]<mailto:[email protected]>;
[email protected]<mailto:[email protected]>;
[email protected]<mailto:[email protected]>
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 <[email protected]<mailto:[email protected]>>
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 (
[email protected]<mailto:[email protected]> ).
/Loa
for the mpls wf co-chairs
PS
I'm copying the spring working group on this mail.
--
Loa Andersson email: [email protected]<mailto:[email protected]>
Senior MPLS Expert
Bronze Dragon Consulting phone: +46 739 81 21 64
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