Network association algorithm

[Walter Bender]

Wad,

Thanks for writing this up. A few additional comments:

(1) We need to characterize the amount of time necessary at each step
and--at some point--tune the algorithms. For example, we probably
don't want to wait 30 seconds for each attempt at DHCP.

(2) We need to expose the status at all steps in the UI. We also
probably want to enable the child to jump into the flow at different
points from the UI, such as going directly to search for AP or forcing
back to the search for a school server.

(3) We need to determine the most efficient way to know if the state
of the mesh has changed such that we should reenter the process. E.g.,
what if you move away from the school server and you had been an MPP.
Now you have to look for an MPP... There are many anomalous cases we
need to consider.

(4) It was proposed that we dedicate one of the LEDs to indicate a AP
connection and the other to indicate an MPP connection.

One thing we didn't discuss at all and is probably something we don't
do for the time being is some sort of gain control. If we have a
crowded classroom, I assume it would be better to turn down the volume
on the radios so that everyone is not shouting, but just quietly
talking to their neighbors. Maybe we want to add an outer loop to the
whole thing where you start off whispering and gradually crank up the
volume until you have a connect?

-walter

On 5/1/07, John Watlington <wad at laptop.org> wrote:
>
> Dan,
>    I'm pretty sure that the attached flowchart documents the network
> association algorithm developed in today's meeting.
>
> There are four end conditions, in rough order of desirability:
> 1. The XO finds an established MPP (w. DHCP), and uses it for
> internet access.
> 2. The XO finds an AP, and becomes an ad-hoc MPP (no DHCP)
> 3. The XO finds an ad-hoc MPP (no DHCP), and uses it for internet access
> 4. The XO finds no AP nor MPP, and becomes a mesh node on channel 1
> w. no internet access
>
> It has already been pointed out that for optimum performance, we will
> eventually want to
> randomly prefer end condition 3 over condition 2.
>
> Cheers,
> wad
>
>
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-- 
Walter Bender
One Laptop per Child
http://laptop.org