Re: [STDS-802-11-TGM] Extending the Element ID space
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
The TGai fragmentation scheme is in 9.42 and 9.43 of Draft
P802.11ai_D3.0.pdf and looks reasonable to me.
I think the two structures are fine but I'm wonder if there should be
some mechanism to push back against everyone grabbing the shorter
Structure A until it is used up before starting on Structure B. Maybe
Structure A should only be allowed for IEs that have to be in Beacons
or something...
Thanks,
Donald
=============================
Donald E. Eastlake 3rd +1-508-333-2270 (cell)
155 Beaver Street, Milford, MA 01757 USA
d3e3e3@xxxxxxxxx
On Thu, Oct 2, 2014 at 2:33 AM, Stephens, Adrian P
<Adrian.P.Stephens@xxxxxxxxx> wrote:
> --- This message came from the IEEE 802.11 Task Group M Technical Reflector
> ---
>
> Dear TGm folks,
>
>
>
> In the September meeting there was a discussion of the likely exhaustion of
> Element ID space, and a clear sentiment to
>
> be proactive in resolving the issue.
>
> TGai has just asked the ANA for 14 of the remaining ~20 Element IDs, so we
> need to consider a possible extension mechanism urgently.
>
>
>
> In my mind the requirements of any extension are: (most important first)
>
>
>
> 1. To be parseable by existing parsers
>
> 2. To support an effectively unlimited number of Element IDs. For this
> purpose 2**16 might be “unlimited”.
>
> 3. To minimise added overhead
>
> 4. To permit longer elements
>
>
>
> I don’t see how we can satisfy 1. and 4. simultaneously, but brighter minds
> may find a solution.
>
> (OK, I can see a complex solution, but not a simple one).
>
>
>
> I suggest, as a starting point to stimulate discussion, the following
> structures:
>
>
>
> Structure A: - 8 bit extension, 8 bit length
>
> Octet 1: Element ID = 254
>
> Octet 2: Length (1-255), including Octet 3
>
> Octet 3: Element ID Extension 0-255
>
> Octets 4 to Length+3: Body
>
>
>
> Structure B: - 16 bit extension, 8 bit length
>
> Octet 1: Element ID = 255
>
> Octet 2: Length (2-255), including Octets 3 and 4
>
> Octets 3-4: Element ID Extension 0-65535, less one escape
>
> Octets 5 to Length+3: Body
>
>
>
>
>
> Regarding lengths greater than 255, we already have a fragmentation scheme
> in TGai. I don’t see an obvious
>
> scheme that doesn’t need “compatibility element header mid-ambles” of some
> kind. The complexity of such
>
> a scheme is similar to the fragmentation scheme of TGai, so there is little
> benefit to inventing it.
>
>
>
> I suggest we have an email thread. If there is a consensus emerging, I
> suggest those folks get together
>
> in a submission to TGmc for the November session.
>
>
>
>
>
>
>
> Best Regards,
>
>
>
> Adrian P STEPHENS
>
>
>
> Tel: +44 (1793) 404825 (office)
> Tel: +44 (7920) 084 900 (mobile, UK)
>
> Tel: +1 (408) 2397485 (mobile, USA)
>
>
>
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