[Cerowrt-devel] Multicast IHUs [was: perverse powersave bug with sta/ap mode]

Juliusz Chroboczek jch at pps.univ-paris-diderot.fr
Thu Apr 28 13:10:49 EDT 2016

> 1) Well, I have suggested that IHU messages actually be unicast rather
> than bundled with the hello.

Yes, you have suggested that before.  I answered I would implement that if
somebody volunteered to do an experimental evaluation.  Nobody volunteered.

> That would help somewhat in this case.

That's my intuition too, but I've learned to be wary of my intuitions.
Doing wireless stuff without careful evaluation is not something I'll do

> 2) A protocol that needs "always listening" capability could signal
> the underlying stack to "make sure" these packets hit the air, and one
> that also wants "please be lossy" capabl
> I leave the actual implementation of that request to the fantasies of
> the authors - a new dscp codepoint or three?
> /me ducks

No need to duck, Dave, it's very similar to what was done with UDP-Lite,
where the use of a specific value in the protocol field signals the link
layer not to discard corrupted frames.  I've never seen it in the wild,
I wonder why.

> 4) And ya know - it might merely be a (sadly common) bug. Everybody's
> supposed to wake up for the multicast beacons and get a notification
> there's more data to come.

Yes, it's obviously a bug.  Just like you, I'm not suprised -- ad-hoc mode
and power save is the kind of thing that's never tested.  I suggest you
disable power saving on all your nodes and be done with it.

-- Juliusz

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