Curiosity question - Bandwidth using RMAN duplicate from Serivce

I don't know of any reason why a channel itself would be throttled. I can understand a channel not being able to read enough from disk to fill up the network card, so I'm guessing in theory 1 channel could use all the available bandwidth if it was reading from disk fast enough?

Key question:
I wonder how you could determine the correct number of channels if you know your disk read rate to avoid hammering your network bandwidth going out of the server?

(Note: I recently pegged a network card on a production server doing an RMAN duplicate and I've been puzzling over this since then - doesn't help that our production server had one network card only)