Balance function of a flow-level network
= Balance function of a flow-level network
{title2=$n_rx_r(n)=\Phi(n-e_r)/\Phi(n)$}
A positive balance function $\Phi$ expresses each active route's aggregate service as this ratio. With independent Poisson arrivals and exponential document sizes, <detailed balance> yields stationary weights $\Phi(n)\prod_r\rho_r^{n_r}$, provided their sum is finite.