event the sdh path 20 is not terminated and packets on the sdh path 20 are made to pass through to a next node cut through 1 in this method not only the termination of the sdh path for example vt1 5 but also the operation in a second layer 23 or a third layer 24 fig5 become unnecessary therefore it is possible to save a considerable amount of functions furthermore a packet delay at this node includes no more than a delay required for the packets on the sdh path 20 to pass through a first layer 22 thus the packets can pass through this node without any substantial delay turning back to fig3 the cut through node will be described in conjunction with the specific example at the point e the packets of y corporation and z corporation need not be dropped therefore at the point e the private line y sdh path 11 or the private line z sdh path 12 need not be subjected to any operation at all the cut through is executed by the private line x sdh path 10 alone referring to fig5 the private line x sdh path 10 has a throughput of n u00d7 vt1 5 n being.