Embodiments are directed towards receiving packets communicated over at least one network, determining layer 3 header information for the received packets, normalizing the determined layer 3 header information for each received packet, employing a determined value based on the normalized layer 3 header information to detect each received packet that is a duplicate, disregarding duplicate packets, and enabling monitoring and analysis of at least selected flows that include packets that are determined to be non-duplicated. Also, if the determined layer 3 header information indicates that the received packet is fragmented, that packet is de-fragmented at least in accordance with a fragment offset. Additionally, normalization may include at least one of masking at least one value in the layer 3 header information, or rolling back changes in the layer 3 header information.