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

• A、a class can be identified as a single application， multiple applications with similar service needs，or be based on the source or destination IP address
• B、a drawback of the DiffServ field in the MAC header to mark frames into behavior aggregates （BAs）
• C、DiffServ uses the DiffServ field in the MAC header to mark frames into behavior
• D、the DiffServ field occupies the same eight bits of the MAC header that were previously used for the ToS field
• E、the first six high-order bits of the DiffServ field are used to identify the Resource Reservation Protocol （RSVP） value
• F、the primary goal of DiffServ is scalability