A collection of specialized classes are used to to implement
per-flow statistics gathering.
These classes include:
QueueMonitor/ED/Flowmon, QueueMonitor/ED/Flow, and Classifier/Hash. Typically, an arriving packet is inspected to determine to which flow it belongs. This inspection and flow mapping is performed by a classifier object (described in section 21.7.1). Once the correct flow is determined, the packet is passed to a flow monitor, which is responsible for collecting per-flow state. Per-flow state is contained in flow objects in a one-to-one relationship to the flows known by the flow monitor. Typically, a flow monitor will create flow objects on-demand when packets arrive that cannot be mapped to an already-known flow.