1. A computer implemented method for network monitoring, the method comprising: providing, using a hardware processor, network packet event characterization and analysis for network monitoring that comprises supporting summarization and characterization of network packet traces collected across multiple processing elements of different types in a virtual network; and providing an aggregate view of what is happening with the virtual network, wherein the providing includes a trace slicing to organize individual packet events into path-based trace slices, a trace characterization to extract at least 2 types of feature matrix describing those trace slices, and a trace analysis for clustering, ranking and querying packet traces based on metrics of the feature matrix, wherein the clustering includes constructing clusters of trace slices based on a similarity of paths of packets, the ranking is based on one or more of a plurality of types of packet feature vectors, and the querying includes traversing all the packet feature vectors to generate a list of items meeting all query conditions; and wherein the network packet trace summarization and characterization for network monitoring enables diagnosing data-path routing problems in the network and enables new network visualization and traffic analysis.