RE: Re: xAP - The Proposed Architecture Explained...

["BUTLER, Tony, FM" <roaming@xxxxxxx>]

> Not if you use multicast and a switch.

I'm not quite sure what you mean by that.  If you *broadcast* a
message,
then it goes to every device on the network AIUI

Wasn't this one of the problems when Doom came out - networks ground to
a
halt because it was broadcasting lan game info to the entire
network....
I know you're unlikely to have the same volume of data as in a 3d game,
but
with normal network traffic too, it all adds up....

> 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

True.  It depends on how many inputs and how many outputs and the
sample
frequency - eg if you are monitoring the temperature continuously, then
you
would be flooding the network with messages (albiet small ones) when of
your
12 disply devices, only one actually cares about the temperature
message.
Maybe too much traffic would _never_ be an issue in this system, is just
a
thought......

> 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!

I wouldn't say that was a very big issue at all - how do machines talk
to
each other now?
Even if it was down to MAC address, so what?  The user isn't going to
see
it.....
ith DHCP AIUI, you wake up go 'hello, can I have an IP', you get one,
and
you can then go 'thanks, now here's my name'.  So you could just go by
name.

It doesn't seem to be an issue restricted to the subscription model
either,
as if you broadcast everything to all outputs, they have to decide
themselves what they want to see - so how do they know which device the
data
is coming from and if they should care about it?
Same problem it seems to me.


Tony


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