PURPOSE: To grasp a delay state at a data block transmission side exchange by sending a delay measurement data signal periodically from the data exchange to another data exchange and measuring the time up to the reception of a corresponding delay measurement answer data signal.
CONSTITUTION: A data switching network 10 consists of plural data exchanges 11-1n, inter-office trunk lines 21-2n which connect the respective exchanges, etc., and the respective exchanges are accommodated with data terminals 31-3n. Further, the data terminals make a communication through a data switching network. The respective data exchanges have a response delay time measurement table 50 shown in a figure (a), an input control display table 60 shown in a figure (b), an answer delay time reference value table 70 shown in a figure (c) and a transmission stop time display table 80 shown in a figure (d), and the data exchanges compare the delay measurement answer data signal reception time 52 with the answer delay time reference value 71 and set an in-input-control display (FLG) 61 in the table 60 when the time 52 is larger than the reference value (A) 71 to stop sending data blocks to the corresponding data exchanges for a certain time.
NAGAO MIYAO
SUGANUMA ATSUHIKO
NIPPON TELEGRAPH & TELEPHONE
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