As I'm not the only one using the machines I've tested my program on and I'm not aware of the network parameters used, I can only guess the startup-time and bandwidth.
When looking at the results with a data-amount of 2¹⁶ double values it can be derived, that the machines the program was tested on, must be connected to a 100 Mbit network, as the results show a maximum transfer rate of about 90 Mbit/s.

Looking at the results with a data-amount of one or two double-values it can be seen, that in this case the transfer-time does not really play a role. So startup-time must be in a range of 50µs and 100µs. Such low start-up times are necessary to make a large number of (short) consecutive transfers in a LAN possible.

The overall communication-time nearly doubles with a doubling of the amount of data transferred, what could in fact be expected.