[RTG-DIR] RtgDir Last Call review: draft-ietf-raw-ldacs

[Tal Mizrahi <[e-mail]>]

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-raw-ldacs-08
Reviewer: Tal Mizrahi
Review Date: 2021-09-01
Intended Status: Informational

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

*Comments:*

The draft provides an overview of the L-band Digital Aeronautical
Communications System (LDACS), which is a work-in-progress standard by the
ICAO standardization group. The draft is well-written, and is almost ready
for publication, with a few comments that follow.

*Major Issues:*

   - Although the abstract clearly explains that LDACS includes support for
   IPv6, the reader later learns that LDACs is mostly a Layer 2 technology,
   and that IPv6 over LDACS has not been defined yet. The document does not
   describe the connection between LDACS and IPv6, why IPv6 was chosen (and
   not IPv4), and the challenges of using IPv6 over this technology. It would
   be worthwhile to add a paragraph or two about this to the introduction.
   - Specifically, it would be  useful to add a paragraph that explains how
   LDACS is related to IETF protocols, and whether any work is expected in the
   IETF in this context.

*Other Issues:*

   - Minor issues are concerns about clarity or technical accuracy that
   should be discussed and resolved before publication, but which would
   normally be resolved between the authors and the reviewers.
   - Please include all of the minor issues you have found. Give as much
   context information as possible (e.g., section numbers, paragraph counts).
   - If you find no minor issues, please write: "No minor issues found."

*Nits:*
- It would be useful to mention in the introduction in which parts of the
world LDACS is expected to be deployed, and whether any geographical
restrictions are expected in the context of this technology.

- Throughout the document the word "shall" (lowercase) is used often. It is
not clear whether this is because this text refers to the future tense, or
whether because this is phrased as a requirement. I would suggest to replace
the word "shall" by a different word, or to explain at the beginning what
it means in this document.

- Abstract:
  "High reliability and availability for IP connectivity over LDACS are
therefore essential."
  It would be useful to also mention security in this sentence.

- Introduction:
  "efficient aircraft control and safe separation"
  Please clarify what you mean by separation (perhaps separation between
entertainment system traffic and aircraft control traffic?).

- Introduction:
  The following sentence is mentioned in Section 4. Maybe it would be
useful in the introduction.
  "LDACS standardization within the framework of the ICAO started in
   December 2016.  The ICAO standardization group has produced an
   initial Standards and Recommended Practices document [ICA2018]."

- Section 3:
  The term "Business Communication" is used several times. It would be
useful to define what this means.

- Section 5:
  The word "RECOMMENDS" (uppercase) is used here. This is not a standard
RFC2119 key word. Please change it to lowercase.

- Section 5:
  "Regulatory this is considered related to the safety and regularity"
  Please consider rephrasing this sentence. It is not clear.

- Section 8:
  "FL and RL boundaries are aligned in time"
  Please mention what is the method used for synchronizing the time.

- Section 9:
  Figure 2 presents the LDACS protocol stack, where IPv6 is illustrated
above the SNP layer. It would be useful to have some text in Section 9.5
that explains how the SNP layer is connected to the IPv6 layer, and why
IPv6 is used here (vs. IPv4).

- Section 10:
  "Reasons for Wireless Digital Aeronautical Communications"
  This title does not really fit the section - please consider rephrasing
it.

- Section 10.2:
  Typo: LADACS ==> LDACS

- Section 11:
  "Privacy Considerations"
  The text in this section is not related to privacy. I would suggest
removing this section completely.

- Reference section:
  Please review the "normative references" section. I would move all the
references to "informative", unless you find that one of these is
absolutely required as normative.

- Please remove [RFC2119], as it is not used in the document.