Subject: [Raw] Intdir telechat review of draft-ietf-raw-ldacs-10

From: Carlos Bernardos via Datatracker <[email-masked]>
Date: Mon, 18 Apr 2022 00:23:37 -0700

Reviewer: Carlos Bernardos
Review result: Not Ready

I am an assigned INT directorate reviewer for draft-ietf-raw-ldacs. These
comments were written primarily for the benefit of the Internet Area Directors.
Document editors and shepherd(s) should treat these comments just like they
would treat comments from any other IETF contributors and resolve them along
with any other Last Call comments that have been received. For more details on
the INT Directorate, see https://datatracker.ietf.org/group/intdir/about/
<https://datatracker.ietf.org/group/intdir/about/>.

Based on my review, if I was on the IESG I would ballot this document as
DISCUSS.

I have the following DISCUSS/ABSTAIN level issues:

- As stated by the routing review, I think the point of not having an
specification of IPv6 over LDACS is a bit troublesome: "There is currently no
"IPv6 over LDACS" specification publicly available; however, SESAR2020 has
started the testing of IPv6-based LDACS testbeds." The main value of this
document to IETF, in the context of RAW, is to understand the characteristics
of IPv6 over LDACS and the requirements of aeronautical trafffic using LDACS in
terms of reliability and availability.

- It is mentioned that handover between LDACS cells is seamless, automatic and
transparent to the user --> does this mean transparency to the IPv6 layer? how
is this done, what type of service/interface (and associated link model) do
provide LDACS L2 to IPv6? I think the most relevant part of the LDACS protocol
stack for the IETF is the section 7.3.3 (LDACS Sub-Network Layer and Protocol
Services), which basically says that this is "ongoing work"

- "Technically the FCI multilink concept will be realized by multi-homed mobile
IPv6 networks in the aircraft." --> how is Mobile IPv6 going to be used and
which specific protocol of the Mobile IPv6 family? just MIPv6 and/or PMIPv6?
implications on mobility and RAW are unclear at this point (probably this is
for the RAW WG to evaluate, but just wanted to point it out).

The following are other issues I found with this document that SHOULD be
corrected before publication:

- The objectives of the document are not clear in the abstract. Since this is a
RAW WG document, it is about explaining a technology that might be used by
future RAW solutions, and the goal of the document is present its
characteristics with that angle in mind. I think this needs to be better
explained, to set the right reader expectations. I think it should also be
mentioned that LDACS standardization is not actually finished, and therefore
this document is a snapshot of current status.

- There is a lot of very good information about LDACS and context on
aeronautical communications in the document, but I wonder if part of it should
be maybe moved to an annex to keep tha main body focused on the actual
implications to IETF (and specifically RAW) of the use of LDACS.

The following are minor issues (typos, misspelling, minor text improvements)
with the document. Just some below (I think other directorate reviews did a
very good job identifying some):

- "It assumes a star-
   topology in each cell where Aircraft Stations (AS) belonging to
   aircraft within a certain volume of space (the LDACS cell) is
   connected to the controlling GS." -->

   "It assumes a star-
   topology in each cell where Aircraft Stations (AS) belonging to
   aircraft within a certain volume of space (the LDACS cell) ARE
   connected to the controlling GS."