A method of automatically establishing differentiated services quality of service treatment for a return packet flow that is associated with an originating packet flow in a network is disclosed. The originating packet flow is received, and it is determined that one or more packets in the originating packet flow are marked with a DSCP value that matches a policy rule that instruct setting of a specified DSCP value to the return packet flow. In response, information identifying the originating packet flow and a second DSCP value for marking the return packet flow is created and stored. When a corresponding return packet flow is received and determined to be associated with the originating packet flow, packets of the return packet flow are automatically marked with the second DSCP value. Once the packet flow terminates, all stored information is removed.