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 first packets of a plurality of data packets of an elastic stream (flux élast) received; - a step of queueing of said first packets of the elastic stream received; - a step of determining the priority level of said elastic stream (flux élast) received; - a step of interrogating a chart, said chart being adapted to store an optimal path (W opt) for a high priority level of an elastic stream (flux élast) and at least one acceptable path (W acc) for a lower priority level 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 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 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 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 first packets of a plurality of data packets of an elastic stream (flux élast) received; - a step of queueing of said first packets of the elastic stream received; - a step of determining the priority level of said elastic stream (flux élast) received; - a step of interrogating a chart, said chart being adapted to store an optimal path (W opt) for a high priority level of an elastic stream (flux élast) and at least one acceptable path (W acc) for a lower priority level 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 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 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 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).