Comments on draft-ietf-6man-multicast-addr-arch-update-02

Jouni Korhonen <jouni.nospam@gmail.com> Mon, 10 February 2014 09:23 UTC

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From: Jouni Korhonen <jouni.nospam@gmail.com>
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Subject: Comments on draft-ietf-6man-multicast-addr-arch-update-02
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Date: Mon, 10 Feb 2014 11:23:37 +0200
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Sorry being a bit late but I had a read of this document. 

** Some nits:

s/[ADDRARCH]/[RFC4291]

** While I agree this document is needed there is a general procedural
issue I have. This I-D patches three other RFCs, which over the time
may become an issue. I would rather see each document having their
own bis and RFC4291 update being the master on all of these updates. I
recon it might be awfully late for this, though.

** Section 4.1:

   NEW:

         |   8    |  4 |  4 |   8    |    8   |       64       |    32    |
         +--------+----+----+--------+--------+----------------+----------+
         |11111111|flgs|scop|reserved|  plen  | network prefix | group ID |
         +--------+----+----+--------+--------+----------------+----------+
                             ^^^^^^^^

Shouldn't this also be align with other NEW formats? Others have a new set
of "flgs" + "rsvd" here.

** In all proposed updated address formats we seem to have the following:

    |   8    |  4 |  4 |  4 |..
    +--------+----+----+----+----+--------+----------------+----------+
    |11111111|flgs|scop|flgs|..                                       | 
    +--------+----+----+----+----+--------+----------------+----------+
              ^^^^^^^^^^^^^^

I find this confusing having two distinct sets of "flgs". Why not concatenate
that to one 12 bits field? Or at least name the latter "flgs" differently?

Either way current statements like in Section 4.2 

                                         +-+-+-+-+
         flgs is a set of four flags:    |X|R|P|T|
                                         +-+-+-+-+

are wrong, since there are now two sets of "flgs" that sum up to eight flags.


Therefore I would propose for example the following format:

    |   8    |      12      | ..
    +--------+----+----+----+----+--------+----------------+----------+
    |11111111|flgs_and_scop | ..                                      | 
    +--------+----+----+----+----+--------+----------------+----------+

Then describe the "flgs_and_scop" as

    11       7       3     0
    +-+-+-+-+-+-+-+-+-+-+-+-+
    |X|R|P|T| scope |r|r|r|r|
    +-+-+-+-+-+-+-+-+-+-+-+-+

where "rrrr" are for future assignment as additional flag bits.

Or alternatively:

    |   8    |  4 |  4 |  4 |..
    +--------+----+----+----+----+--------+----------------+----------+
    |11111111|flgs|scop|newf|..                                       | 
    +--------+----+----+----+----+--------+----------------+----------+

where "newf" are for future assignment as additional flag bits.



** Section 5 IANA Considerations:

   This document may require IANA updates.  However, at this point it is
   not clear exactly what these updates may be.

I find this statement rather sloppy. At least the authors should
give a try listing possible impacts & updates.

- Jouni