Re: xAP - The Proposed Architecture Explained...

["PatrickLidstone" <patrickl@xxxxxxx>]

--- In ukha_d@y..., "BUTLER, Tony, FM" <roaming@f...>
wrote:
> > The proposed architecture is such that there will be, on the 
> > "network", multiple different "input" devices
all 
> > BROADCASTING their information.
> > 
> > It will be up to each individual "output" device to
determine 
> > which of those messages it treats as things to display, and 
> > which it treats as potential triggers.
> 
> Mark, I haven't been following this thread completely, so forgive 
me if this
> has already been discussed.
> If you are boradcasting these messages all over the place, then as
the
> number of devices increases, you are generating shed loads of 
traffic that
> maybe only one or two (or even no) outputs is interested in.

Not if you use multicast and a switch.


> Have you considered a subscription based model where each output 
device
> subscribes to the service they are interested in (Marks unread 
count,
> outside temp etc) and the controlling pc or whatever only sends 
event data
> specifically to those devices which requested it.
>
> I know a bit more intelligence is required on the display and 
server side,
> but would save on potentially flooding the network with traffic - 
especially
> if you were monitoring something realtime....

The messages are small. A broadcast message travels once on the wire, 
a point-point message once for each device. The efficiency tradeoff 
might not be as straightforward as it looks. The difficulty is not so 
much maintaining the subscription lists at each device - as 
maintaining the naming conventions and mappings of the 
interconnections. How will you configure which device is connected to 
which device? If you're using IP, and a device retrieves it's address 
by DHCP, what happens when the device reboots -- you probabably end-
up maintaining lists of MAC addresses. Not very friendly!

Patrick

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