In packet networks, the data rate, measured in bit per second (bps), in excess of the Committed Information Rate (CIR) to which a public carrier network will allow a virtual circuit (VC) to burst during periods of no congestion. If the EIR is set to zero (i.e., disabled), the VC can burst up to the full port speed. If the EIR is set to a non-zero (i.e., enabled) the VC can burst up to a rate equal to CIR+EIR, but no more than the full port speed. During periods of congestion, the VC is throttled back to the CIR speed. Frames in excess of the CIR are marked discard eligible (DE), which means that they may be discarded in the event of congestion within the network core. Frame relay and Resilient Packet Ring (RPR) employ CIR and EIR mechanisms. ATM services offer similar features based on cell counts. See also bandwidth, carrier, CIR, DE, frame relay, packet, RPR, and VC.