Which two statements are true about the implementation of QoS？（）

• A、Implementing DiffServ involves the configuration of RSVP.
• B、Implementing IntServ allows QoS to be performed by configuring only the ingress and egress devices.
• C、Implementing IntServ involves the utilization of RSVP.
• D、Traffic should be classified and marked by the core network devices.
• E、Traffic should be classified and marked as close to the edge of the network as possible.