A network monitoring and network congestion analysis can be performed based on a comparison of data packets at multiple different network nodes installed at different locations on a communication path. A downstream network node may be installed at a user location while an upstream network may be installed at an access router further up the network. A network congestion analyzer may receive data packet information including timestamps from both network nodes, and may compare the data packet information to group the data packets into application flows and match the corresponding packets from the different network nodes. Based on the data packet matching, the network congestion analyzer may calculate packet loss, packet delay, packet delay variation, and perform other network congestion analysis techniques for the application flows corresponding to a user's various devices and the applications executing on those devices.