A method in a communication network includes receiving a data unit that includes a request
to transmit an aggregate data unit to a communication device, and, in response to receiving
the data unit, generating an aggregate data unit for transmission to the communication
device, where the aggregate data unit includes a plurality of component data units, each
having a respective media access channel (MAC) header, and a duration of the aggregate
data unit is determined using a parameter negotiated with the communication device.