Telechat Review of draft-ietf-roll-efficient-npdao-12
review-ietf-roll-efficient-npdao-12-rtgdir-telechat-gray-2019-07-08-00

Amy pointed out that I forgot to include the RTG-Dir mailing list in this.

I got a reply from Alvaro, and I had included the ROLL mailing list.

I also sent a follow-up correction as I had gotten paste all over myself.

--
Eric

From: Eric Gray
Sent: Thursday, June 27, 2019 12:41 AM
To:
draft-ietf-roll-efficient-npdao@ietf.org<mailto:draft-ietf-roll-efficient-npdao@ietf.org>
Cc: Alvaro Retana (aretana) <aretana@cisco.com<mailto:aretana@cisco.com>>;
roll@ietf.org<mailto:roll@ietf.org> Subject: Last Call Review of
draft-ietf-roll-efficient-npdao

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-roll-efficient-npdao
Reviewer: Eric Gray
Review Date: 26 June 2019
IETF LC End Date: 26 June 2019
Intended Status: Standards Track

Summary:
Perhaps I am missing some subtleties, but this document looks like it may need
a little more work before it is published.

Overall comments:
The document is mostly well written.

Issues:

In the introduction, I have some trouble parsing “an optional messaging” –
perhaps it was meant to just be “optional messaging?”

There are difference between the abstract (which claims the document describes
issues with NPDAO) and the Introduction (which goes further to say that the
document also discusses requirements and specifies a new message intended to
meet the requirements and solve the problems.

So, it’s a problem statement, requirements document and solution specification
all rolled into one.  I guess this is not a problem for anyone in the WG?

The title for section 1.3 should probably be “Why is NPDAO Important.”

In that section, I have to wonder if saving memory is the most important factor
in removing route information that is no longer valid.  What about issues with
forwarding packets toward destinations that can no longer be reached along that
path?

Perhaps I misunderstand the approach, but it seems to me that the problems
mentioned in section 2.1 should self-resolve.  The fact that one node cannot
send messages to another node to inform that node that it has no DAO
information seems kind of irrelevant if the node, or the link connecting it, is
no longer there.

Perhaps the issue you’re really trying to describe is with unreliable links and
nodes, as opposed to missing links and nodes?  That would make sense in a
low-power and lossy network.

If the behavior described in section 2.2 is common, and a more reasonable
behavior is not anticipated by the original NPDAO specification, than I agree
that is a problem.

If the problems described in 2.1 and 2.3 do exist, it seems likely that the
underlying issue is really about an assumption of reliable delivery where that
might not be the reality.

All of this said, the 3 requirements seem reasonable at least as far as they
go.  There seems to be an implied requirement to introduce at least some level
of reliability (as I seems intended by providing the DCO-ACK). And there
probably should be a requirement to support compatibility with deployed
implementations.

AFAICT, this document does not describe how nodes using the newly specified
messaging and behavior would be compatible with deployed nodes.  Minimally the
document should be clear if the intention is not to provide for compatibility. 
There are at least a couple of indications that there is deployment.