When would you use one of the connections over the other?
Which would be the optimum ethernet connection from the network switch?
NETWORK is the optimum connection coming from the internet.
Direct Stream is used in you had another device attached that the K30 was acting as server for, for example using a S30 as an end-point elsewhere
Thank you Mark.
Last query on the flexibility of this function.
If an ethernet cable is connected from the K30 Direct Stream to a wall point, which feeds to a patch panel, is it possible for an S30 in another location plugged into the same patch panel circuit, able to play the content of the of the K30 server?
If this is possible, could an S30 access both the function above, plus able to play from audio streaming services, Qobuz and the like, obviously not at the time?
Yes and at the same time 
Thank You again and very useful to know for future.