  We analyze how the performance of a quantum-repeater network depends on the
protocol employed to distribute entanglement, and we find that the choice of
repeater-to-repeater link protocol has a profound impact on communication rate
as a function of hardware parameters. We develop numerical simulations of
quantum networks using different protocols, where the repeater hardware is
modeled in terms of key performance parameters, such as photon generation rate
and collection efficiency. These parameters are motivated by recent
experimental demonstrations in quantum dots, trapped ions, and nitrogen-vacancy
centers in diamond. We find that a quantum-dot repeater with the newest
protocol ("MidpointSource") delivers the highest communication rate when there
is low probability of establishing entanglement per transmission, and in some
cases the rate is orders of magnitude higher than other schemes. Our simulation
tools can be used to evaluate communication protocols as part of designing a
large-scale quantum network.
