Patent ID: 9344347
Filing Date: 2016-05-17
CPC Classification: H04L

Claim Text:
1. A delay time measuring apparatus for measuring a delay time from transmission of data to reception of a response to the transmission, the apparatus comprising: a storage control section, coupled to a storage device, which receives a first data packet, as well as a second data packet subsequent to the first data packet, transmitted from a source unit to a destination unit and stores first and second sequence numbers and first and second data lengths of the received first and second data packets in the storage device, together with records indicating first and second receiving times of the received first and second data packets, and which receives ACK packets returned from the destination unit to the source unit and stores ACK numbers of the received ACK packets in the storage device, together with a record indicating receiving time of each received ACK packet, the first and second lengths being integers which are greater than zero; and a calculation section which detects an ACK packet whose ACK number is equal to a sum of the second sequence number and second data length of the second data packet, calculates a difference between the ACK number of the detected ACK packet and the ACK number of an ACK packet received immediately before the detected ACK packet, determines that the source unit has transmitted the second data packet without waiting for an ACK packet corresponding to the first data packet when the difference is greater than the second data length of the second data packet, and calculates a delay time based on the second receiving time of the second data packet and the receiving time of the detected ACK packet, the delay time being calculated by eliminating a delayed ACK packet, in order to evaluate the quality of the network by measuring the delay time, the delayed ACK packet being returned from the destination unit to the source unit after a predetermined delay.