Last Call Review of draft-ietf-mpls-spring-entropy-label-08
review-ietf-mpls-spring-entropy-label-08-rtgdir-lc-ceccarelli-2018-02-21-00

Hello,

I have been selected as the Routing Directorate reviewer for this draft. The
Routing Directorate seeks to review all routing or routing-related drafts as
they pass through IETF last call and IESG review, and sometimes on special
request. The purpose of the review is to provide assistance to the Routing ADs.
For more information about the Routing Directorate, please see
​http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir

Although these comments are primarily for the use of the Routing ADs, it would
be helpful if you could consider them along with any other IETF Last Call
comments that you receive, and strive to resolve them through discussion or by
updating the draft.

Document: draft-ietf-mpls-spring-entropy-label

Reviewer: Daniele Ceccarelli

Review Date: 2018/02/20

IETF LC End Date: date-if-known

Intended Status: Informational

Summary:

I have some minor concerns about this document that I think should be resolved
before publication.

Comments:

The document is well written and I really appreciated the detailed examples and
the analysis of the options described in section 10. My only concern, in
addition the minor issues listed below, is the scope of the document. It is an
informational document and the abstract says it examines and describes how Els
are applicable to segment routing. Reading the text it seems it is much more.
There are requirements and procedures describer in the document as well as
requirements and RFC2119 language is often used. Maybe it’s worth considering a
better scoping of the document?

Major Issues:

None

Minor Issues:

  *   Introduction: “Entropy label (EL) [RFC6790] is a technique used in the
  MPLS data plane to provide entropy for load-balancing.” Providing an intro on
  what an EL is can be very useful, but a bit more or explanation is needed,
  just a couple of sentences. *   Section 1.1 – Is this needed? The abstract
  says “This document examines and describes how ELs are to be applied to
  Segment Routing” and the status is informational. I’m not sure RFC2119
  language is needed. E.g. in section 4 “A router capable of reading N labels
  but not using an EL located within those N labels MUST consider its ERLD to
  be 0”.  Further reading the document I see constraint against e.g. the ERLD
  are defined. Maybe it is more appropriate to say that the document also
  describes the requirements for the usage of EL in SPRING MPLS ? Moreover in
  section 6 it seems to describe procedures, so it’s even more than
  applicability and requirements. *   Section 3: I don’t understand what this
  sentence means. Can you rephrase? “As each MPLS node may have limitations in
  the number of labels it can push when it is ingress or inspect when doing
  load-balancing, an entropy label insertion strategy becomes important to keep
  the benefit of the load-balancing.

Nits:

- Abstract: suggest avoid repetition of “applied” as well as examines and
describes. What about: “This document describes how Els can be  applied to
Segment Routing with an MPLS data plane.

- Section 6: “In term of packet forwarding, by learning the mapping-server
advertisement from PE5,”…it should be P5 not PE5.

- Section 6: “   To accomodate the mix of signalling protocols involved during
the

   stitching, the entropy label capability SHOULD be propagated between the
   signalling protocols.” Not clear what this means, maybe it should be
   propagated between the two domains, not the signaling protocols?

Thanks,

Daniele