Methods and systems for managing the actions that are applied to packet flows by packet processing systems. A packet processing system maintains a flow table, i.e., a list of active flows and respective actions to be applied to the flows. The system classifies each incoming packet into a respective flow, and processes the packet in accordance with the action that is specified for this flow in the flow table. Typically, the system deletes a packet flow from the flow table when it becomes inactive, e.g., when no packets belonging to the flow arrive within a certain time-out period.