A.Voice traffic should be marked to DSCP EF per the QoS baseline and RFC3246.
B.Voice traffic loss should be no more than 3%.
C.One-way latency （mouth-to-ear） should be less than 150 msec.
D.Average one way jitter should be targeted to less than 30 msec.
E.21-320 Kbps of guaranteed priority bandwidth is required per call depending on sample rate，codec，and  layer 2 overhead.