Asterisk.conf highpriority=yes ? to set tos=ef

Are there any drawbacks to setting highpriority=yes in asterisk.conf ?

Is this the best way of getting asterisk to set the tos fields to ef … at least without having to mess with iptables, which I don’t want to.

I have done a tcpdump and see that rtp traffic tos is being set to 0xb8 which is what I want for our Cisco WAN QoS implementation.

Any pointers would be most helpful here.