CIR

The CIR is the guaranteed rate, in bits per second, that the service provider commits to providing.
Committed Burst
The maximum number of bits that the switch agrees to transfer during a time interval. (It is noted Bc)
Excess Burst
The maximum number of uncommitted bits that the Frame Relay switch attempts to transfer beyond the CIR. Excess burst is dependent on the service offerings available by the vendor, but is typically limited to the port speed of the local access loop.
Forward Explicit Congestion Notification (FECN)
A bit set in a frame that notifies a DTE that congestion avoidance procedures should be initiated by the receiving device. When a Frame Relay switch recognizes congestion in the network, it sends a FECN packet to the destination device, indicating that congestion has occurred.