Yes. You can use class of service (CoS) within MPLS networks to prioritize certain types of traffic during periods of congestion. Juniper Networks EX Series Ethernet Switches support Differentiated Service Code Point (DSCP) or IP precedence and IEEE 802.1p CoS classifiers on the customer-edge interfaces of the ingress provider edge (PE) switch. DSCP or IP precedence classifiers are used for Layer 3 packets. IEEE 802.1p is used for Layer 2 packets.
For more information, click Junos OS MPLS for EX Series.