A method for creating a supplementary subflow as a supplement to a subflow existing in a multipath network connection using a transport protocol suited to a multipath communication mode. The multipath network connection is implemented in a network comprising a source using said multipath network connection for communicating with a receiver via an intermediate network component. Following an opening of an intermediate communication path between the intermediate network component and the receiver, said intermediate network component implements the following steps: obtaining a packet intended for the source; creating a header representing a request to create said supplementary data packet subflow, the supplementary data packet subflow being intended to use the intermediate communication link; inserting said header in said packet; and transmitting said packet to the source so as to cause the initiation, by the source, of a procedure for creating said supplementary data packet subflow.