Frame Relay Traffic Policing provides a mechanism to rate-limit packets on switched PVCs using a "leaky-bucket" implementation. When enabled, Traffic Policing prevents traffic congestion by discarding or setting the Discard Eligible (DE) bit on packets that exceed specified traffic parameters. Traffic Policing parameters can be specified per DCE interface, or per switched PVC, using the 'map class' mechanisms.
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The Class-Based Policer for the DiffServ AF PHB feature is based on RFC 2697 A Single Rate Three Color Marker. The packet stream is metered and packets are marked "conform," "exceed," or "violate." Marking is based on a Committed Information Rate (CIR) and two associated burst sizes, a Committed Burst Size (CBS) and an Excess Burst Size (EBS). A packet is marked "conform" if it does not exceed the CBS, "exceed" if it exceeds the CBS but not the EBS, and "violate" otherwise.