Re: Re: xPL announcement/description protocol -- was xPLDiag

[Gerry Duprey <gerry@xxxxxxxxxxx>]

Howdy,

>>already configured and starts straight away, if it starts
>>before the hub it could be up to 9 minutes before the hub
>>receives the next hbeat from the app and starts sending xPL
>>messages to it - and that is not good.
>
>
> I agree it's not good, but I also think it's incorrect?
>
> 1) if hub starts after the app, the next hbeat is at most 5 minutes
away (so
> 5 minutes max wait, assuming default interval)?

But for the duration of that wait, the application will not be able to
receive xPL messages (until the hub hears from it, the hub doesn't know to
forward messages to it).

The idea of the quick heartbeat is that 1) in 99% of the cases, there is a
hub already running with the xPL app starts so there really is only one
heartbeat sent and immediately replied to (after which things go back to
normal) and 2) that when the app is running before the hub, this will
generally be a short duration issue (like a system rebooting and devices
not
starting in the most optimal/predictable order), so even then, the quick
heartbeat rate will likely only run for a few shots before the hub echoes
and things get back to normal.

In a bad case where there is no hub ever, one packet every 3 seconds is not
very much network traffic (a small fraction of a 1% percent of bandwidth)
and after some period of time, even that dies down a bit.

I really feel that with the separate hubs and the new hub discovery stuff
(rapid heartbeats), xPL has made an important step forward in being
responsive and robust.

Gerry

--
Gerry Duprey
Ann Arbor, MI 48103
http://www.cdp1802.org