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Telechat Review of draft-ietf-ccamp-flexi-grid-fwk-05

Request Review of draft-ietf-ccamp-flexi-grid-fwk
Requested revision No specific revision (document currently at 07)
Type Telechat Review
Team General Area Review Team (Gen-ART) (genart)
Deadline 2015-08-04
Requested 2015-07-30
Authors Iftekhar Hussain , Xihua Fu , Fatai Zhang , Daniele Ceccarelli , Oscar Gonzalez de Dios , Ramon Casellas
I-D last updated 2015-08-07
Completed reviews Genart Last Call review of -05 by David L. Black (diff)
Genart Telechat review of -05 by David L. Black (diff)
Secdir Last Call review of -05 by Sam Hartman (diff)
Opsdir Last Call review of -05 by Tina Tsou (Ting ZOU) (diff)
Assignment Reviewer David L. Black
State Completed
Review review-ietf-ccamp-flexi-grid-fwk-05-genart-telechat-black-2015-08-07
Reviewed revision 05 (document currently at 07)
Result On the Right Track
Completed 2015-08-07
I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at


Please resolve these comments along with any other Last Call comments
you may receive.

Document: draft-ietf-ccamp-flexi-grid-fwk-05
Reviewer: David Black
Review Date: August 2, 2015
IESG Telechat date: August 6, 2015

Summary: This draft is on the right track, but has open issues
 		described in the review.

This draft requires significant GMPLS expertise to fully understand,
but is generally well written and clear.  It describes the use of a
GMPLS control plane with flexible optical networks that can vary
optical frequency assignment on a per-link basis along an optical

All of the issues that I found are minor, and some of them may
be mostly reflections of my lack of GMPLS expertise.

Major issues: None

Minor issues:

[1] 3.2.5 - the last bullet item is not completely clear to me.  What
does it mean for two slot compositions to be the same?  Is this saying
that the same set of effective frequency slots need to be present
end-to-end for the media channel?  I suspect not, but I don't understand
what is intended.

[2] p.21 last sentence in 1st para:

   Regardless of the actual encoding,
   the LSP setup message specifies a minimum frequency slot width that
   needs to be fulfilled in order to successful establish the requsted

Should "minimum frequency slot width" be "minimum effective frequency slot
width"?  I think it's  possible for the effective frequency slot width to
be smaller than all of the individual slot widths involved in the absence
of frequency shifters/converters.

[3] p.21 - RSA acronym is unfortunate, due to collision w/widespread usage
of that acronym for a security algorithm.  I strongly suggest changing to
another acronym (e.g., R+SA).

[4] 4.8.4 - The information model is informal or abstract (can't generate
anything from it), even though RBNF was used - this should be noted.

[5] 5.5 - I'm surprised that the first requirement (neighbor discovery
support) is a MAY.  I wonder about its operational consequences, and at the
very least suggest expanding Section 8 to discuss them.  The text in 5.5
should be expanded to add some explanation of how things work when there's
no neighbor discovery support.

Nits/editorial comments:

Section: 3.2.1 - Editorial suggestion: Changing "+" -> "+/-" in the
formula for nominal central frequency and re-defining n as a
non-negative integer would be slightly clearer.

p.6 - please state that slot width is +/- wrt nominal central frequency.

p.8 - Fig 4 could use a bit more explanation - the two frequency
slots occur at different points along the path.

Nit: First nominal central frequency 'X' in Fig 5 needs to move 2
chars left.

Section 4 - TE link term shows up w/o acronym expansion or definition.
Please define it before use.

Sections 4.2 and 4.3 - this may be my unfamiliarity, but it would have
helped to have some sort of heads-up at the start of the figures that
the top (non-GMPLS) portion of the figures prior to Figure 12 are
entirely in the optical domain.  Perhaps explaining what the two
planes are (and how they're realized/implemented) in Figure 8 would help.

Last paragraph on p.16: "trnaponders" -> "transponders".  Also, I saw
"transceivers" earlier - if that's the same concept, only one term
should be used.

p.19 - Even after expanding acronyms, I don't understand this sentence:

   If two OTSis must be
   switched to different ports, it is better to carry them by different
   FSC channels, and the media layer switch is enough in this scenario.

A sentence or two explaining what an "FSC channel" is earlier in that
paragraph would help.

p.21, 1st para:

   messages, and a specific frequency slot can be requeste on any



   In GMPLS the requested effective frequency slot is represented to the
   TSpec present in the Path message, and the effective frequency slot
   is mapped to the FlowSpec carried in the Resv message.

I believe those are RSVP-TE messages - that should be stated.

p. 22:

   d.  n can change, but m needs to remain the same along the path.
       This ensures that the effective frequency slot remains valid, but
       allows the frequency slot to be moved within the spectrum from
       hop to hop.

In full generality, that may require the ability to shift or convert a
frequency slot, which is a concept that doesn't appear to occur in the
draft prior to this point.

Figures 15 and 16 need their variables (e.g., m_a, FSb) somehow
labelled or explained

After Figure 16, the switch to the EFS acronym is a surprise, given
the extensive prior usage of the spelled-out term.  This paragraph
contains all uses of the EFS acronym - I suggest removing that acronym
and spelling out the term.

Section 4.6: I don't understand why this sentence is in the middle of
the paragraph - it doesn't seem to describe an example of different
slot width granularities:

   Consider a node with an application where the nominal
   central frequency granularity is 12.5 GHz and where slot widths are
   multiples of 25 GHz. 

I'd suggest removing it.

5.1.1. What is L-band?  This is the first time it's mentioned.

idnits 2.13.02 didn't find anything that needs attention.

David L. Black, Distinguished Engineer
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786 at        Mobile: +1 (978) 394-7754