[6lo] Tsvart last call review of draft-ietf-6lo-plc-05

Joseph Touch via Datatracker <noreply@ietf.org> Sat, 20 February 2021 01:15 UTC

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Date: Fri, 19 Feb 2021 17:15:14 -0800
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Subject: [6lo] Tsvart last call review of draft-ietf-6lo-plc-05
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Reviewer: Joseph Touch
Review result: Ready with Issues

This document has been reviewed as part of the transport area review team's
ongoing effort to review key IETF documents. These comments were written
primarily for the transport area directors, but are copied to the document's
authors and WG to allow them to address any issues raised and also to the IETF
discussion list for information.

When done at the time of IETF Last Call, the authors should consider this
review as part of the last-call comments they receive. Please always CC
tsv-art@ietf.org if you reply to or forward this review.

---

The only significant transport issue in this doc is the issue of MTU support.
Secs 3.3 and 4.6 refers to underlying frag/reassembly per RFC4944. First, these
sections seem redundant; normative requirements should appear in only one
section if both are retained.

More notably, the use of a 16-bit tag in that spec is already known to be
problematic for IPv4 fragmentation and could cause problems here as well, e.g.,
per RFC4963. This issue should be addressed, notably if there is a reason why a
16-bit tag is considered sufficient for this use it should be stated or some
other shim layer should be proposed with a more robust tag (e.g., 32 bits).

Some minor additional suggestions follow:

The intro refers to “6lo”; this term should be defined before being used. The
scenarios should include a citation if available. Similarly, LLN should be
defined. Work that did not receive consensus might be mentioned elsewhere or
even omitted completely, but seems premature in the intro. Also, “the previous
work” in the last sentence is ambiguous; it would be useful to refer to the
RFCs, the draft, or whatever else to which it refers.

Sec 3 includes “Moreover, recently a new …”, which seems redundant; it might be
just “A new…”. Again, this section (and later ones too) refers to “6lo” as a
category of sorts, which needs to be defined (and included in the
acronym/terminology list).