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.