Data transmission method by a mobile station comprising a step of determining the mds

The invention concerns a data transmission method in accordance with a communication protocol from a mobile station (10) consisting of a smart card (SIM) associated with a mobile host equipment (ME), said protocol being organised in several layers including at least a data transport layer of the datagram type adapted to transmit integrally data packets (D) of a maximum size (MDS). The invention is characterised in that said transmission method comprises a step which consists, for the card (SIM), in determining the value of said maximum size of data packets (MDS) capable of being integrally transmitted by the transport layer of its mobile host equipment (ME).