Which description of the Russian Doll Model is true?
The Russian Doll Model (RDM) is a hierarchical Quality of Service (QoS) model used in computer networking. It is named after the Russian dolls that fit inside one another, with each smaller doll representing a nested subset of the larger doll. Similarly, in RDM, QoS policies for different traffic classes are nested within each other, with each lower-level class inheriting policies from the higher-level classes.
Option A is incorrect because it talks about limiting the aggregate of reserved bandwidth, which is not a feature of RDM. In RDM, each class is guaranteed a minimum amount of bandwidth, and any unused bandwidth is shared among all classes.
Option B is partially correct. RDM does guarantee a minimum amount of bandwidth for each class type, but it does not define two pools for each class type. Instead, it uses a hierarchical approach where lower-level classes inherit policies from higher-level classes.
Option C is incorrect because RDM is primarily used for bandwidth allocation and does not directly protect against QoS degradation. However, it can indirectly help protect against QoS degradation by ensuring that each class has a minimum amount of bandwidth.
Option D is the most accurate description of RDM. It provides both bandwidth sharing and isolation, as well as service differentiation for different priority services. RDM achieves this by using a hierarchical approach, where policies for lower-level classes are inherited from higher-level classes. This allows for flexible and efficient allocation of bandwidth while still ensuring QoS for different traffic classes.