A routing method for routing an elastic stream (flux élast ) in a transport network , said transport network having a plurality of nodes and links between said nodes, said elastic stream (flux élast ) comprising a plurality of data packets, said elastic stream having a priority level selected from among at least two priority levels (N1, N2), wherein said routing method comprises: - a step of detecting (E1) first packets of a plurality of data packets of an elastic stream (flux élast ) received; - a step of queueing (E2) of said first packets of the elastic stream received; - a step of determining (E3) the priority level of said elastic stream (flux élast ) received; - a step of interrogating (E4) a chart , said chart being adapted to store an optimal path (W opt ) for a high priority level (N1) of an elastic stream (flux élast ) and at least one acceptable path (W acc ) for a lower priority level (N2) of an elastic stream (flux élast ), said optimal path (W opt ) and said acceptable path (W acc ) having been determined previously as a function of characteristics of nodes of the transport network and/or as a function of links between said nodes and/or as a function of measurements representative of the flow of data streams on each link of the transport network , said representative measurements being collected continuously; - a step of establishing (E5) the optimal path (W opt ) or the acceptable path (W acc ) in the transport network according to the priority level of the elastic stream (flux élast ) received, said establishing step (E5) setting rules for the flow of data streams on each of the links followed by the optimal path (W opt ) or by the acceptable path (W acc ); - a step of releasing (E6) the first packets of the elastic stream (flux élast ) received for them to be forwarded by the transport network via the optimal path (W opt ) or via the acceptable path (W acc ). - a step of detecting (E1) first packets of a plurality of data packets of an elastic stream (flux élast ) received; - a step of queueing (E2) of said first packets of the elastic stream received; - a step of determining (E3) the priority level of said elastic stream (flux élast ) received; - a step of interrogating (E4) a chart , said chart being adapted to store an optimal path (W opt ) for a high priority level (N1) of an elastic stream (flux élast ) and at least one acceptable path (W acc ) for a lower priority level (N2) of an elastic stream (flux élast ), said optimal path (W opt ) and said acceptable path (W acc ) having been determined previously as a function of characteristics of nodes of the transport network and/or as a function of links between said nodes and/or as a function of measurements representative of the flow of data streams on each link of the transport network , said representative measurements being collected continuously; - a step of establishing (E5) the optimal path (W opt ) or the acceptable path (W acc ) in the transport network according to the priority level of the elastic stream (flux élast ) received, said establishing step (E5) setting rules for the flow of data streams on each of the links followed by the optimal path (W opt ) or by the acceptable path (W acc ); - a step of releasing (E6) the first packets of the elastic stream (flux élast ) received for them to be forwarded by the transport network via the optimal path (W opt ) or via the acceptable path (W acc ). <EOS>