In the design of a QoS solution， which two factors should be taken into consideration？（）

A. On congested links， all forms of traffic will require some form of Qo
B. All traffic types and requirements should be examined to determine the number of traffic classes required.
C. In the implementation of link efficiency mechanisms on links that typically transport relatively large packets， header compression will be most efficient.
D. In the implementation of link efficiency mechanisms on links that typically transport relatively small packets， header compression will be most efficient.
E. In the implementation of link efficiency mechanisms on links that typically transport relatively small packets， payload compression will be most efficient.
F. Payload compression provides more available bandwidth and reduces processing delay time.