In the Linux world, the term traffic control represents all the possibilities to influence incoming and outgoing network traffic in one way or another. In this context, we normally distinguish between two definitions, although it is often difficult to draw a clear line between the two:
Policing: "Policing" means that data streams are monitored and that packets not admitted by a specified strategy (policy) are discarded. Within a networked computer, this can happen in two places: when it is receiving packets from the network (ingress policing) and when it is sending packets to the network.
Traffic shaping: "Traffic shaping" refers to a targeted influence on mostly outgoing traffic. This includes, for example, buffering of outgoing data to stay within a specified rate, setting priorities for outgoing data streams, and marking packets for specific service classes.
The traffic-control framework developed for the Linux operating system creates a universal environment, which integrates totally different elements for policing and traffic shaping that can be interconnected. These elements can even be dynamically loaded and unloaded as a module during active operation. We describe this framework in detail below, but limit the discussion of the implementation of elements in this framework to a single example. Subsequently, we will describe configuration options in the user space.
