A method of header compression steps, performed by a first processor, of receiving a first packet-header sent from a second processor, the first packet-header having been sent in response to the second processor receiving the first packet-header encapsulated in a frame, and the frame not matching a flow table entry in the second processor. The method also includes sending a first signal to the second processor; sending a first flow table entry to the second processor; sending a second signal to a third processor; and sending a second flow table entry to the third processor. The first signal causes the second processor to generate substitute data in response to subsequently receiving a second packet-header, the substitute data being shorter that the second packet-header, the substitute data corresponding to the first signal. The second signal causes the third processor to generate the second packet-header, responsive to the substitute data subsequently received from the second processor, in accordance with the second signal.