1. A computer-implemented method of monitoring a portion of a network, wherein a network monitoring device among a plurality of network monitoring devices has been assigned to monitor the portion of the network, said method comprising: determining, by the network monitoring device, a logical grouping of nodes for the portion of the network to which the network monitoring device has been assigned; determining, by the network monitoring device, a hierarchy that ranks nodes within the logical grouping, wherein the network monitoring device prunes the hierarchy based on a capacity of the network monitoring device; receiving, by the network monitoring device, network traffic information corresponding to nodes within the logical grouping; and selectively storing, by the network monitoring device, network traffic corresponding to the nodes within the logical grouping according to their respective positions within the hierarchy.