Subject: [lp-wan] Mirja Kühlewind's No Objection on draft-ietf-lpwan-ipv6-static-context-hc-21: (with COMMENT)

From: Mirja Kühlewind via Datatracker <[email-masked]>
Date: Wed, 21 Aug 2019 09:38:15 -0700

Mirja Kühlewind has entered the following ballot position for
draft-ietf-lpwan-ipv6-static-context-hc-21: No Objection

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COMMENT:
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Thanks for the well-written document!

A few quick comments:

1) This text on ECN in sec 10.3:
    " ECN functionality depends on both bits of the ECN field, which are
      the 2 LSBs of this field, hence sending only a single LSB of this
      field is NOT RECOMMENDED."
probably belongs in section 10.2 instead, no?

2) If I understand the protocol correctly, I believe it should be a normative
requirement that the Inactivity Timer is always larger than the Retransmission
Timer? Related to this, Appendix F says: "The initial value of the Inactivity
timer is
   expected to be greater than that of the Retransmission timer, in
   order to make sure that a (buffered) SCHC Fragment to be
   retransmitted can find an opportunity for that transmission.  One
   exception to this recommendation is the special case of the All-1
   SCHC Fragment transmission."
I think this section should be moved into the body of the document. Further, if
you need a different timer value for the All-1 SCHC Fragment, you should give
this timer a distinct name and value.

3) I also agree with Alvaro that appendix E should be moved into the body of
the document if you intent to specify something normatively there.

4) Editorial in Sec 10.11:
"...with a strength that is identical or better to the UDP
   checksum."
Not sure what you mean by "better"...?

5) I wondering if you want to say maybe something about pacing out different
fragments (mostly when a window is used). I know that any recommendation would
be technology dependent but in some cases sending a burst of packets e.g. could
overload some network queues; therefore it could be good to at least mention
it...?

6) Without having thought too hard about it: is it possible with this
compression scheme to specify a rule that increases a counter/sequence number
by 1 (given the initial value is known)? Would maybe be nice to say something
about this in the document...