Rather than model-net LPs directly sending messages to other model-net LPs, LPs
can route the intended message through the scheduler interface to be queued up
for reception by the receiver (see the diff of loggp.c). This has the benefit of
    enabling things like priority and fairness for N->1 communication patterns.
    Currently, no packetizing is supported, and I haven't yet wrote checks for
    it - beware.

Loggp is currently the only supported model. simplenet could also be supported
without much trouble, but I doubt there's any demand for it at the moment.  This
should NOT be used by the dragonfly/torus models, as they have their own routing
backend.