Which description of the Russian Doll Model is true?
A. RDM provides bandwidth sharing while providing bandwidth isolation and protection against QoS degradation, and also provides service differentiation for high-priority, normal- priority and besteffort priority services
B. RDM matches simple bandwidth control policies setting individual bandwidth constraint for a given class type and simultaneously limit the aggregate of reserved bandwidth across all class types
C. RDM can be used simultaneously to ensure bandwidth efficiency and to protect against QoS degradation of all class types, whether preemption is used or not
D. RDM guarantees a predefined amount of bandwidth for each type and at the same time allows the bandwidth sharing by defining two pools for every class type: private pool (guaranteed bandwidth) and common pool (bandwidth shared between all class types)
