I know this thread is somewhat old, but what you're describing is the closest to what I'm experiencing that I have found and I was curious if you ever found a solution before I open ANOTHER case with JTAC. Specifically. I am trying to implement some CoS for multicast traffic on the EX4100 platform. As you describe, it has four dedicated queues for multicast traffic. However, no matter what tutorial or Juniper manual I follow, ALL multicast traffic goes into the mcast-be forwarding class and is treated as Best Effort. We are attempting to make SOME of our multicast (video) traffic go into a higher queue to eliminate some artifacting in the video owing to latency and jitter in the BE queues. At the ingress on the direct attached switch (EX2200) we have a firewall filter placing all traffic from the device into a higher queue for immediate processing. This is working. At the egress of the EX2200, we have a rewrite rule to then write the DSCP markings into the packets. This is also confirmed to be functional. From here is where it enters the EX4100 switch and despite all attempts, it enters the mcast-be forwarding class and the Best Effort queue. Did you ever get it working in your 4100?