Traffic shaping is a mechanism to reduce the rate at which data is transmitted over an interface. Traffic shaping refers to the related technology of traffic policing. Policing works by either adjusting the priority of excess traffic to a lower queue or discarding the excess traffic. As with RED, discarding TCP traffic has the effect of throttling the stream by forcing the window size to shrink and decreasing its transmission rate. Because RTP is a fixed-bandwidth application, discarding RTP packets reduces voice quality without altering the transmission rate. Adjusting the priority of voice traffic removes the strict priority protection that reduces latency and jitter and offers the highest voice quality. Therefore, in most cases, it is beneficial to use QoS mechanisms rather than traffic shaping and policing to offer the highest quality for voice.