Re: [6lo] [IANA #1200929] expert review for draft-irtf-icnrg-icnlowpan-10

[Cenk Gündoğan <[e-mail]>]

Hello Pascal,

the compressed NDN Interest + compressed NDN Data message dispatches
have a few RSV bits.  Fixing the prefix on 4 bits might work for them.
For the compressed CCNx Content Object message it already works since we
removed the RSV bit in the proposed solution.

Currently, the compressed CCNx Interest message dispatch consumes two
full octets and has no RSV bits left.  That's the source of the
asymmetry.  I'll have a look at that particular section to see if we can
optimize something there and will report again.

Thanks,
Cenk

On Thu, Sep 23 2021 at 07:31 +0000, Pascal Thubert (pthubert) wrote:

> Hello Amanda;
>
> The current draft has this:
>
>     +-------------+------+-------------------------------------------+
>     | Bit Pattern | Page | Header Type                               |
>     +-------------+------+-------------------------------------------+
>     |  00 000000  | TBD1 | Uncompressed NDN Interest messages        |
>     |  00 100000  | TBD1 | Uncompressed NDN Data messages            |
>     |  01 000000  | TBD1 | Uncompressed CCNx Interest messages       |
>     |  01 100000  | TBD1 | Uncompressed CCNx Content Object messages |
>     |  10 0xxxxx  | TBD1 | Compressed NDN Interest messages          |
>     |  10 1xxxxx  | TBD1 | Compressed NDN Data messages              |
>     |  11 0xxxxx  | TBD1 | Compressed CCNx Interest messages         |
>     |  11 1xxxxx  | TBD1 | Compressed CCNx Content Object messages   |
>     +-------------+------+-------------------------------------------+
>
> The Uncompressed form has the 4 rightmost bits set to 0 while the compressed has them xxxxx.
> Which leaves lots of unassigned space un the Uncompressed range.
>
> This simple proposal seems to break the symmetry of compressed forms.
>
>
>     |  10 0xxxxx  | TBD1 | Compressed NDN Interest messages          |
>     |  10 1xxxxx  | TBD1 | Compressed NDN Data messages              |
>     |  10 0xxxxx  | TBD1 | Compressed CCNx Interest messages         |
>     |  11 10xxxx  | TBD1 | Compressed CCNx Content Object messages   |
>
> Maybe 4 bits is sufficient in all compressed forms? If so we can do better:
>
>     +-------------+------+-------------------------------------------+
>     | Bit Pattern | Page | Header Type                               |
>     +-------------+------+-------------------------------------------+
>     |  00 000000  | TBD1 | Uncompressed NDN Interest messages        |
>     |  00 000001  |      |                                           |
>     |    ...      |      |      Unassigned                           |
>     |  00 001111  |      |                                           |
>     |  00 01xxxx  | TBD1 | Compressed NDN Interest messages          |
>     |  00 100000  | TBD1 | Uncompressed NDN Data messages            |
>     |  00 100001  |      |                                           |
>     |    ...      |      |      Unassigned                           |
>     |  00 101111  |      |                                           |
>     |  00 11xxxx  | TBD1 | Compressed NDN Data messages              |
>     |  01 000000  | TBD1 | Uncompressed CCNx Interest messages       |
>     |  01 000001  |      |                                           |
>     |    ...      |      |      Unassigned                           |
>     |  01 001111  |      |                                           |
>     |  01 01xxxx  | TBD1 | Compressed CCNx Interest messages         |
>     |  01 100000  | TBD1 | Uncompressed CCNx Content Object messages |
>     |  01 100001  |      |                                           |
>     |    ...      |      |      Unassigned                           |
>     |  01 101111  |      |                                           |
>     |  01 11xxxx  | TBD1 | Compressed CCNx Content Object messages   |
>     +-------------+------+-------------------------------------------+
>
> Works?
>
> Pascal
>
> This leaves unassigned space 
>
>> -----Original Message-----
>> From: Amanda Baber via RT <[e-mail]>
>> Sent: mercredi 22 septembre 2021 19:30
>> Cc: Eric Vyncke (evyncke) <[e-mail]>; [e-mail];
>> [e-mail]; [e-mail]; Pascal Thubert
>> (pthubert) <[e-mail]>; [e-mail]; [e-mail]
>> Subject: [IANA #1200929] expert review for draft-irtf-icnrg-icnlowpan-10
>> 
>> Hi,
>> 
>> IANA has been asked to notify the 6lo group and the authors of RFC 8025 as
>> well as the IESG-designated experts that the authors of draft-irtf-icnrg-
>> icnlowpan-10 (and the RG) have accepted a proposed change to an assignment
>> in that document.
>> 
>> Carles and Shwetha, can you confirm that we can move forward with this
>> registry update?
>> 
>> The issue is that Table 2 in https://datatracker.ietf.org/doc/html/draft-
>> irtf-icnrg-icnlowpan is currently instructing IANA to make this
>> registration in the Dispatch Type Field registry (we understand that this
>> "TBD1" should be page 14):
>> 
>> 11 1xxxxx | TBD1 | Compressed CCNx Content Object messages
>> 
>> However, 11 11xxxx has already been assigned to "Page switch" for pages 0-
>> 15:
>> 
>> https://www.iana.org/assignments/_6lowpan-parameters
>> 
>> This is the solution suggested by the experts and accepted by the authors:
>> 
>> =====
>> 
>> One simple solution could be as follows:
>> 
>> OLD:
>> 11 1xxxxx | TBD1 | Compressed CCNx Content Object messages
>> 
>> NEW:
>> 11 10xxxx | TBD1 | Compressed CCNx Content Object messages
>> 
>> A drawback of this solution is that it reduces the space of this type of
>> messages (from 32 options to 16 options, for this specific type of
>> messages), but perhaps it could be sufficient.
>> 
>> =====
>> 
>> The authors write, "The simple solution provided by the designated experts
>> is sufficient. The drawback does not affect the option space, since that
>> particular dispatch also contains a 'Reserved' bit. We can trade this for
>> the longer prefix '11 10xxxx' (instead of '11 1xxxxx')."
>> 
>> Best regards,
>> 
>> Amanda Baber
>> IANA Operations Manager
>
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--

Cenk Gündoğan

Hamburg University of Applied Sciences
Dept. of Computer Science / Internet Technologies Group
Berliner Tor 7, 20099 Hamburg, Germany
Fon: [phone] - 8426
Mail: [e-mail]
Web: https://www.inet.haw-hamburg.de/