This constitutes the signal or transport layer of the network." d) Physical layer: this is the medium that caries the signal (wire, fibre, wireless).243 407 Mr. Hatfield states that there are greater barriers, both economic and operational to duplication of the lower layers in the protocol stack.
» d) Couche physique : c'est le support qui achemine le signal (filaire, fibre optique, sans fil).243 407 M. Hatfield indique qu'il existe de plus grands obstacles, tant économiques que techniques, à la reproduction des couches inférieures de la pile de protocoles.