Which two statements about the DiffServ QoS model are true？（）

• A、DiffServ requires RSVP to set up a path through the network to accommodate the requested QoS.
• B、Network traffic is identified by class， and the level of service is chosen for each class.
• C、The DiffServ model relies on a fairly simple mechanism to provide QoS over a wide range of equipment.
• D、RSVP enables the DiffServ model to provide end-to-end QoS.
• E、The DiffServ model is more scalable than the IntServ model.
• F、The flow-based approach of the DiffServ model is ideal for large scalable implementations such as the public Internet.