  We propose a limited packet-delivering capacity model for traffic dynamics in
scale-free networks. In this model, the total node's packet-delivering capacity
is fixed, and the allocation of packet-delivering capacity on node $i$ is
proportional to $k_{i}^{\phi}$, where $k_{i}$ is the degree of node $i$ and
$\phi$ is a adjustable parameter. We have applied this model on the shortest
path routing strategy as well as the local routing strategy, and found that
there exists an optimal value of parameter $\phi$ leading to the maximal
network capacity under both routing strategies. We provide some explanations
for the emergence of optimal $\phi$.
