Traffic Shaping
Traffic shaping also controls the amount of traffic sent out an interface, but
shaping buffers excess traffic instead of dropping it. Because data is usually
bursty, the buffered traffic can be sent out between bursts. Thus, shaping
smoothes out the flow of traffic. This also results in fewer packet drops, and
thus fewer TCP retransmits. It does, however, introduce some delay for
traffic that must be buffered. It does not support remarking traffic.
Some uses for shaping include:
■ Making the outgoing traffic rate match the contracted committed information
rate (CIR).
■ To avoid overrunning remote links in networks, such as ATM, Frame
Relay, and Metro Ethernet, that might have different bandwidths on
hub and spoke devices.
■ Interacting with Frame Relay congestion notifications, causing the
router to throttle-back its sending rate.
Class-based traffic shaping is configured under the policy map. It works with
any type of interface, not just Frame Relay interfaces.