Traffic Monitor: A system that can measure the peak and average traffic from or to a set of destinations. An ISP that bases fees on use needs a traffic monitor to measure the traffic for each customer.
Traffic Policer: A system used to discard traffic that exceeds a predetermined threshold according to a specification given by the network administrator. An ISP that charges for levels of service can use a traffic policer to ensure that a given customer does not transmit more data than authorized.
Traffic Shaper: A system that delays some packets and allows others to pass through quickly according to a set of specifications. Some routers offer traffic shaping. ISPs use traffic shaping to prevent congestion and to give priority to customer who pay more. By forcing traffic to adhere to stream policer without being discarded.
Packet analyzer: A system that attaches to a network and captures copies of packets to measure network performance. Packet analyzers are used to detect problems and measure load.