1. A method for testing a network, comprising: receiving a plurality of packets, each packet including a packet group identification number identifying the packet as a member of one of a plurality of flows; measuring and storing flow statistics for each of the plurality of flows; and analyzing in near real-time at least a portion of the stored flow statistics using a hierarchical array of processors, wherein analyzing further comprises: a lower tier of the hierarchical array of processors filtering the plurality of flows according to a first criterion to select a subset of flows from the plurality of flows, the lower tier of the hierarchical array of processors grouping the flows of the selected plurality of flows into a plurality of aggregation groups according to a second criterion, the lower tier of the hierarchical array of processors aggregating at least some of the stored flow statistics for the each of the plurality of aggregation groups to provide first-tier aggregated flow statistics for each of the plurality of aggregation groups, and at least one higher tier of the hierarchical array of processors further aggregating at least some of the first tier aggregated flow statistics.