What is CBS (committed burst size)?

Committed burst size (CBS) indicates the greatest number of bytes that can be communicated into the network in a short time span. As the time interval tends to zero, the committed burst size addresses the number of bytes that can be transmitted into the network.
CBS is applicable to a service running over Ethernet networks. It is the number of allocated bytes accessible for bursts of service frames that are transmitted temporarily at rates above the CIR, while still meeting the SLA given at the CIR.