This is the first forward-direction traffic parameter, whose meaning depends entirely on circuitFwdTDType: it's the Committed Information Rate (CIR) for Ethernet or Frame Relay circuits, or the Peak Cell Rate including both CLP 0 and 1 cells (PCR(0+1)) for ATM-CBR circuits. This is the primary bandwidth-guarantee value an admin sets to define how much throughput this circuit is committed to carry in the forward direction, so getting it right (in the correct units for the selected type) directly determines the circuit's provisioned bandwidth. For example, on a Frame Relay circuit with circuitFwdTDType set to frameRelay(2), setting this to 512000 would commit that circuit to a 512 kbps CIR into the network.