  We construct a simple network model to provide insight into network design
strategies. We show that the model can be used to address various approaches to
network coding, MAC, and multi-packet reception so that their effects on
network throughput can be evaluated. We consider several topology components
which exhibit the same non-monotonic saturation behavior found within the Katti
et. al. COPE experiments. We further show that fairness allocation by the MAC
can seriously impact performance and cause this non-monotonic saturation. Using
our model, we develop a MAC that provides monotonic saturation, higher
saturation throughput gains and fairness among flows rather than nodes. The
proposed model provides an estimate of the achievable gains for the cross-layer
design of network coding, multi-packet reception, and MAC showing that
super-additive throughput gains on the order of six times that of routing are
possible.
