Salut and Suspend/Resume issues

Giannis Galanis giannisgalanis at gmail.com
Tue Feb 19 13:11:00 EST 2008


On Feb 19, 2008 12:55 PM, Benjamin M. Schwartz <bmschwar at fas.harvard.edu>
wrote:

> On Tue, 2008-02-19 at 12:29 -0500, Giannis Galanis wrote:
> > The avahi works is that every several minutes(a predetermined timeout)
> > each host will send multicast request for all peers in its list.
> > Then all peers receiving this request will send a multicast reply.
> >
> > The packets are multicast because the mesh is mobile/dynamic so we
> > dont know where the target is, or which is the ideal route
>
> The problem is that with a timeout of T minutes and N laptops, there is
> a wakeup required every T/N minutes, on average?


The wakeup required is T minutes for every T minutes.
Actually you would need to be awake  for >T  minutes
and suspended for <T minutes to be sure u are ok.

So for T=10min, as in this case:
9off, 11on, 9 off, 11on

but this is not very effective in terms of suspend/resume

>  Based on your
> description, it sounds as if this could be fixed by a small change in
> Avahi's timeout behavior.
>
> If I reach the timeout, I send a broadcast saying "Everyone, what's your
> status?".  In reply, all users send a broadcast "My status is X".  All
> peers receive all of these broadcasts, and reset their timers to zero.
> In this way, all laptops wake up together once every T minutes.
>
> Surely the solution is not this simple...
>
> The problem is that the others wont know YOUR status.
I think the confirmation of status is not "announced/beaconed", but
"requested" first.

But someone from collabora must confirm this
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