Please consider the following example dealing with qos value of ip communicator and ip phone.
sw f1/1-----------ip phone
PC running ip communicator.
mls qos trust cos.
We want our switch to trust dscp value set by ip communicator running on the PC. The question is how do we tell ip phone to trust dscp value set by ip communicator? The command I found " switchport priority extend ( cos VALUE)/ Trust " advices ipphone whether to trust cos value or set it to some dscp value; it does not tell ipphone anything about dscp value.