Re: [mpls] Warren Kumari's No Objection on draft-ietf-mpls-spring-entropy-label-11: (with COMMENT)

[<[e-mail]>]

I have added the following text:
“There may also be a case where a router has a fast switching path (handled by an ASIC or network processor) and a slow switching path (handled by a CPU) with a different ERLD for each switching path. Again, for simplicity reasons, an implementation MAY use the minimum ERLD as the ERLD value for the system.”

I have also highlighted the drawback as per Joe’s comment:
“The drawback of using a single ERLD for a system lower than the capability of one or more specific component is that it may increase the number of ELI/ELs inserted. This leads to an increase of the label stack size and may have an impact on the capability of the ingress node to push this label stack.”


From: Warren Kumari [mailto:[e-mail]]
Sent: Thursday, July 05, 2018 17:08
To: LITKOWSKI Stephane OBS/OINIS
Cc: The IESG; [e-mail]; [e-mail]; BRUNGARD, DEBORAH A; [e-mail]; Loa Andersson; Joe Clarke
Subject: Re: Warren Kumari's No Objection on draft-ietf-mpls-spring-entropy-label-11: (with COMMENT)



On Thu, Jul 5, 2018 at 7:43 AM <[e-mail]<mailto:[e-mail]>> wrote:
Thanks Warren,

I agree with your comments and I will address them in the next revision.

​Thanks!​


You are right (at least from a theoretical point of view) about fast path vs slow path for ERLD. I think for this kind of switching implementation, we have several options: advertising the fast path ERLD (slow path will never be triggered), advertising the slow path ERLD (there is a possibility that slow path will be triggered for each packet), let this configurable by the user. I do not think that this fast path/slow path implementation is still popular at least for the SP router market.

​I'm fine with whatever you select, I just wanted it to be considered.​
W


-----Original Message-----
From: Warren Kumari [mailto:[e-mail]<mailto:[e-mail]>]
Sent: Wednesday, July 04, 2018 20:04
To: The IESG
Cc: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Warren Kumari's No Objection on draft-ietf-mpls-spring-entropy-label-11: (with COMMENT)

Warren Kumari has entered the following ballot position for
draft-ietf-mpls-spring-entropy-label-11: No Objection

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----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------

Thank you for writing this - it provides useful functionality.

Please see Joe Clarke's OpsDir review here:
https://datatracker.ietf.org/doc/review-ietf-mpls-spring-entropy-label-11-opsdir-lc-clarke-2018-06-25/
 - it mirrors comments made by a number of ADs, and also contains a significnat
number of nits (which would make the document better / more readable).

I had a question:
Section 4.  Entropy Readable Label Depth
" The Entropy Readable Label Depth (ERLD) is defined as the number of
   labels a router can both:
   a.  Read in an MPLS packet received on its incoming interface(s)
       (starting from the top of the stack).
   b.  Use in its load-balancing function."
...
"In a distributed switching architecture, each linecard may have a different
capability in terms of ERLD."

In many cases, a device may have a different readable label depth in hardware /
fastpath than it does by punting the packet to the CPU / control plane. Perhaps
the ERLD should be defined as 'Use in its load-balancing function in the
dataplace / fast-path" (or something, this will need some wording).

I'd also like to say that I like Section 10 (Options considered) - sections
like this make a document much more satisfying (otherwise one has niggling
questions like "What didn't they do single ELs at the bottom of the stack?!") -
thank you for including it.

I also have some nits:
Section 1.  Introduction
"The hashing technique is required to perfom a per-flow load-balancing and thus
prevent packet disordering. " 1: Perform is a type 2: While 'disordering'
explains it well, 'reordering' is a much more common term, and will (I think)
cause less confusion.

"The MPLS architecture brings some challenges on the load-balancing as an LSR
(Label Switch Router) should be able to look at header fields that are beyond
the MPLS label stack." "on the load-balancing" doesn't really parse. Perhaps:
"... brings some load-balancing challenges, as..."?

Section 2.  Abbreviations and Terminology
SRGB is not defined on first use, nor it is in the Terminology section. Also,
sorting this alphabetically would be appreciated.



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