Patent ID: 8081663

Claim:
A time synchronization method for synchronizing times of a first apparatus and a second apparatus, the time synchronization method comprising: transmitting, by the first apparatus, a packet to the second apparatus via a relay apparatus that relays the packet, the packet including the time of the first apparatus; receiving, by the relay apparatus, the packet; determining, by the relay apparatus, whether a type of the received packet is time synchronization between the first apparatus and the second apparatus; providing, by the relay apparatus, a value to the packet in case of determining that the type of the packet is time synchronization, the value indicating a reception time of the packet; providing, by the relay apparatus, a difference between the value provided to the packet in the providing of reception time and a current time to the packet upon a transmission of the packet in case of determining that the type of the packet is time synchronization, the difference serving as a delay value; and executing, by the second apparatus, a control for time synchronization based on the time of the first apparatus included in the packet and the delay value provided to the packet.