This read-write enumerated value sets the ATM traffic contract category for a channel, offering a broader set of choices than the basic read-only field - Constant Bit Rate, Variable Bit Rate, Available Bit Rate, Unspecified Bit Rate, or Real-Time VBR - each implying different bandwidth guarantee and burst-tolerance behavior. Admins choose this based on the nature of the traffic the connection will carry, since it drives which policing parameters (like PCR, SCR, MBS) are relevant for that channel. For example, an admin provisioning a channel for latency-sensitive traffic like voice would select rtvbr rather than ubr, which offers no rate guarantees at all.