This read-only field reports the broadband bearer ATM transfer capability negotiated for this SVC, such as constant bit rate (cbr), variable bit rate real-time or non-real-time (vbr-rt/vbr-nrt), or ABR, and the description explicitly notes it doesn't apply to IISP 3.x, UNI 3.x, or Q.2931 signaling. This tells an admin what QoS class the signaling stack actually assigned to a switched virtual circuit at call setup, which determines how the switch schedules and polices its cells. Seeing cktBBearerAtmTransferCapability report vbr-rt(4) on an SVC expected to carry voice traffic would confirm the call correctly negotiated real-time variable bit rate service rather than falling back to best-effort ABR.