  We study the efficiency of the gradient mechanism of message transfer in a
$2-d$ communication network of regular nodes and randomly distributed hubs.
Each hub on the network is assigned some randomly chosen capacity and hubs with
lower capacities are connected to the hubs with maximum capacity. The average
travel time of single messages traveling on this lattice, plotted as a function
of hub density, shows q-exponential behavior. At high hub densities, this
distribution can be fitted well by a power law. We also study the relaxation
behavior of the network when a large number of messages are created
simultaneously at random locations, and travel on the network towards their
designated destinations. For this situation, in the absence of the gradient
mechanism, the network can show congestion effects due to the formation of
transport traps. We show that if hubs of high betweenness centrality are
connected by the gradient mechanism, efficient decongestion can be achieved.
The gradient mechanism is less prone to the formation of traps than other
decongestion schemes. We also study the spatial configurations of transport
traps, and propose minimal strategies for their elimination.
