[Commotion-dev] Throughput advantage to 802.11s support

[Ben West]

Hi Dan,

First off, I believe all of these patches were made against the current
version of the compat-wireless library.  The first patch did happen to
apply cleanly to compat-wireless-2012-09-07 integrated into Attitude
Adjustment, but the second patch failed.

This first patch is to add short slot time support to 802.11a adhoc mode
(i.e. 5GHz only).  Long slots are required for 802.11b/g adhoc mode (i.e.
2.4GHz) to maintain compliant with the standard.

https://patchwork.kernel.org/patch/1835531/

This second patch, on the other hand, will allow short slot slots in
802.11s mode in 2.4GHz and 5.8GHz, which the standard allows.

https://patchwork.kernel.org/patch/2050741/

I do understand Sascha, et al, have expressed criticism for the fact that
the 802.11s draft stipulates an arbitrary maximum of 32 nodes per mesh.
(Thanks to whichever dastardly telco lobbyist...)  However, Antonio of the
Robin Mesh project, who has already incorporated 802.11s into this new
Meshroot firmware stack, mentioned how this limitation is actually 50 nodes
as implemented (??), and that it only applies to the number of neighboring
nodes that a particular node can keep in its local table, not that it is a
limitation on the total # of nodes in a mesh.  I'm still seeking
confirmation on this.

Finally, please do note that I have not had the opportunity to test the
operation of these patches yet.  As for the degree of adoption of 802.11s,
besides in the mac80211 / compat-wireless ecosystem of OpenWRT, indeed that
is still a work in progress.

On Fri, Feb 8, 2013 at 9:10 AM, Dan Staples <
danstaples at opentechinstitute.org> wrote:

>  Are those patches for ad-hoc, or are they for 802.11s? If they speed up
> ad-hoc throughput, I see no reason not to implement them into Commotion.
> But in general, I would be interested in pursuing 802.11s for Commotion
> down the line. Do you know how widespread is 802.11s support is?
>
> Dan
>
>
> On 02/05/2013 04:38 PM, Ben West wrote:
>
> Hi All,
>
> I'm happy to read that the Hackday just past went well!  The roadmap wiki
> page<https://code.commotionwireless.net/projects/commotion/wiki/Hackday-Roadmap-Notes>looks pretty dense, although unfortunately my suggestion would be to
> increase its density by adding *802.11s support*.  My recent work to
> extract Robin/Cloudtrax dashboard stuff into a standalone package was part
> of a larger effort to get a modern replacement for a Robin nodes.  And,
> this is what is now prompting my recommendation for 802.11s support.
>
> Since I have the expectation of remotely re-flashing all the Robin nodes
> in the field sometime soon, I did throughput tests for old vs new to make
> sure I wouldn't be deploying a regression.  And, looks like 802.11g adhoc
> meshing, even under Attitude Adjustment with the latest atheros drivers, is
> *15% to 20% slower* than the ahdemo meshing done by Kamikaze+madwifi
> based Robin firmware!  This performance penalty appears to come from the
> fact adhoc mode require beacons, while ah-demo does not, hence it not being
> supported by the 802.11 standard.  Furthermore, the mac80211 /
> compat-wireless radio drivers currently packaged into OpenWRT appear to
> enforce a maximum 1000ms interval for such beacons.
>
> For 5.8GHz adhoc, a potential work-around is to use short slot-times as
> implemented in this patch:
>
> https://patchwork.kernel.org/patch/1835531/
>
> 2.8GHz adhoc, however, must still use long slot times to remain
> standards-compliant.  The work-around is that 802.11s meshing can use short
> slot times, which this patch implements:
>
> https://patchwork.kernel.org/patch/2050741/
>
> While I do admit that doing speed tests on near-obsolete platforms like
> ath5k would normally yield diminishing returns, these slot-time
> enhancements should apply just as well to ath9k, too.
>
>
> --
> Ben West
> http://gowasabi.net
> ben at gowasabi.net
> 314-246-9434
>
>
> _______________________________________________
> Commotion-dev mailing listCommotion-dev at lists.chambana.nethttps://lists.chambana.net/mailman/listinfo/commotion-dev
>
>
> --
> Dan Staples
>
> Open Technology Institutehttps://commotionwireless.net
>
>


-- 
Ben West
http://gowasabi.net
ben at gowasabi.net
314-246-9434
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