Re: [6lo] Fwd: [Technical Errata Reported] RFC4944 (4359)

I think the text is almost right, however I think "larger than 63" is no
longer appropriate due to the initial 0b01 bit combination. "larger than
127" worked as it implied the most significant bit could be 1. If the
original intent is to be preserved, the following text would make more
sense to me:

ESC:  Specifies that the following header is a single 8-bit field for the
Dispatch value.  It allows support for more than 64 Dispatch values.

Alternatively, Kerry's more relaxed text would also work.

Robert

On 30 May 2015 at 13:35, Kerry Lynn <kerlyn@ieee.org> wrote:

>
>
> On Sat, May 30, 2015 at 3:51 AM, Jonathan Hui <jonhui@nestlabs.com> wrote:
>
> <snip>
>
> Jonathan,
>
> Thanks for the historical background.  I think it will inform the
> discussion on how to fix
> the section going forward.
>
> But putting aside the discussion on the original intent of the value "127"
>> and taking a step back, the high-level intent was to support
>> arbitrary-length bit patterns for identifying 6LoWPAN headers.  It may be
>> that removing any reference to a maximum "dispatch value" offered within
>> the first 8 bits is the best path forward, as Kerry has suggested.
>>
>> No argument here.  I think it's the best that can be done to improve the
> section with a
> one-sentence change.
>
> Kerry
>
>> --
>> Jonathan Hui
>>
>> Grüße, Carsten
>>>
>>>
>>> Jonathan Hui wrote:
>>> > I believe the Erratum under discussion is correct and should be marked
>>> > as Verified.
>>> >
>>> > The original intent of "Dispatch value" was:
>>> > 1) To refer to the Dispatch field in the Dispatch Header - note the
>>> > capitalization in "Allows support for Dispatch values larger than 127."
>>> > 2) To identify a namespace that *excludes* the Mesh Addressing and
>>> > Fragmentation headers.
>>> >
>>> > The original draft text (draft-ietf-6lowpan-format-07) was less
>>> > ambiguous about the original intent.  Referring to that draft:
>>> >
>>> > 1) The draft separated the concept of "Header Type" from "Dispatch
>>> > Value".  The draft defined Header Types: Dispatch, Mesh Delivery, and
>>> > Fragmentation, and Dispatch Values: NALP, IPv6, LOWPAN_HC1, LOWPAN_BC0,
>>> > and ESC.  The draft also includes the following text that indicates the
>>> > Mesh Addressing and Fragmentation headers are not included in the
>>> > dispatch value namespace:
>>> >
>>> >    The definition of headers, other than mesh addressing and
>>> >    fragmentation, in LoWPAN consists of the dispatch value, the
>>> >    definition of the header fields that follow
>>> >
>>> > Note that the text above still lives in RFC 4944.
>>> >
>>> > 2) The bit pattern figure was titled "Dispatch Type Bit Pattern", not
>>> > "Dispatch Value Bit Pattern", with the intent that the table only
>>> > included the initial allocations within the Dispatch Header and did
>>> > *not* include any mention of Mesh Delivery and Fragmentation headers.
>>> >
>>> > --
>>> > Jonathan Hui
>>> >
>>> > _______________________________________________
>>> > 6lo mailing list
>>> > 6lo@ietf.org
>>> > https://www.ietf.org/mailman/listinfo/6lo
>>>
>>
>>
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