Which of these is a valid differentiated services PHB？ （）

A.with traffic shaping，a router stores excess traffic in packet buffers until bandwidth is available again
B.with policing you can tune the buffer usage for traffic exceeding the specified CIR
C.with shaping you can tune the buffer usage for traffic exceeding the specified CIR
D.shaping should only be applied for ingress traffic，policing only for egress
E.policing uses a token bucket algorithm，shaping uses an SPD algorithm

A.Both support normal and extended VLAN ranges.
B.ISL is a Cisco proprietary encapsulation method and 802.1Q is an IEEE standard.
C.ISL encapsulates the original frame.
D.Both support native VLANs.
E.802.1Q does not encapsulate the original frame.