Cumulative count of bytes in the expedited-forwarding ('ef') traffic class, colored yellow (out-of-profile, marked down but not dropped), on the egress side of this SDP. It is one of the eight forwarding-class-by-color bytes counters this MIB exposes per SDP and direction; an admin uses the full set to see how traffic is distributed across the device's eight CoS queues and how much of each class is conforming (green) versus over its committed rate (yellow).