subnet bandwidth manager (QoS) (SBM)
Subnet Bandwidth Manager (SBM) is a concept for quality of service( QoS) in IP networks.
In the Subnet Bandwidth Manager concept, there are several bandwidth managers in a Layer 2 domain. Each physical segment also has a Designated Subnet Bandwidth Manager( DSBM). It controls the resource requirements for the responsible segment. The other SBMs can take over the functions of the DSBM if it fails.