Which two statements are true about the implementation of QoS？（）
- AImplementing DiffServ involves the configuration of RSVP.
- BImplementing IntServ allows QoS to be performed by configuring only the ingress and egress devices.
- CImplementing IntServ involves the utilization of RSVP.
- DTraffic should be classified and marked by the core network devices.
- ETraffic should be classified and marked as close to the edge of the network as possible.