(a) establishing a plurality of tunnels; (b) sending at least one byte to a second network node over a first protocol using a first process of the first network node and a second process of the second network node; (c) if the at least one byte is sent to the second network node successfully, sending the datagrams over the first protocol using the first process and the second process; and (d) if the at least one byte is not sent to the second network node successfully, sending the datagrams over a second protocol using a third process of the first network node and a fourth process of the second network node;

wherein: the datagrams are sent through one selected tunnel in the plurality of tunnels;

the first process and the second process do not handle retransmission;

the first network node is configured to send further datagrams using the first process and the second process to the second network node regardless of a receive-window size (rwnd) limit set by the second network node;

the first network node is configured to receive a flow control message from the second network node when at least one of the datagrams is received by the second network node;

the first network node is configured to continue or to hold off sending the further datagrams based on the flow control message;

each of the first process and the third process is a sending transport layer process; and each of the second process and the fourth process is a receiving transport layer process.