The basic reason it's done like this is that in larger
theatre scenarios, you don't install very much
DMX cabling and rely on
Ethernet distribution of
DMX because one cable can carry so many universes. It's then very easy to insert a
node point anywhere in the building, and configure the
node point to output set universes of
DMX. You're also not limited to any number of
DMX feed locations per
universe. You can have
Universe 1 appear in 20 different places in the
auditorium, or you can have universes 1-12 on LX1 - LX12 with one on each, the choice is all yours and anything in between.
In a major
theatre - especially new builds - you might have hundreds of
ethernet sockets spread around the building. You can have them anywhere you like - on the
stage, in the
grid, on the galleries, in the
FOH boxes, in the control room, in the dressing rooms, whatever you want. And they can all feed back to switches in the control room, where you can easily patch the
network socket on the back of your
console to any location in the whole
theatre. Take yourself a
node (IE a 4-port Gateway) to that location,
plug it in, configure it either from the
console or by plugging a laptop into the
ethernet as well; and then you have whatever
DMX universes you want, instantly accessible in that location.
You can also
network the consoles... you could have an
EOS out in front of
house, but an
ION on
stage, to make it easy for the electricians on
stage to
call up lanterns and focus them. You could also
network things like media servers - so the
media server could be on
stage where there is loads of room, but the
console in
FOH.
It also makes sense as other departments can patch into the
ethernet locations. Sound can use it to control wireless transceivers, video can
send data around the building, or you can
plug cue lights in. Among many other options.
Ethernet infrastructure is a very flexible asset to any modern
theatre, and the nodes / gateway devices that all
console manufacturers now offer is how you can make use of that.