The invention relates to arranging data flow control in a data transfer system comprising a sender and at least two protocol entities serving the transmission of data from the sender. The originating protocol entity of a suspension request primitive is checked. Suspension is set as the data transmission status for the protocol entity that has originated a suspension request primitive. The originating protocol entity of a resume request primitive is checked before sending it to the sender. Also the status information is checked. Transmission of the resume request primitive to the sender is prevented if suspension is set for any other protocol entity than the originating protocol entity of the resume request primitive.