A communication system comprising: a first communication control device; and a second communication control device that makes a connection to the first communication control device through a relay device, wherein the first and second communication control devices are provided between communication devices that perform point-in-time synchronization using a synchronization packet, wherein the first communication control device has a point-in-time assignment unit that assigns first point-in-time information relating to a point in time at which the synchronization packet that is sent from one of the communication devices is received, or a point in time at which the received synchronization packet is transmitted to the relay device, to a packet that is transmitted to the relay device, and wherein the second communication control device includes a communication delay computation unit that, for the synchronization packet, obtains information relating to a communication delay between the first and second communication control devices from second point-in-time information relating to a point in time at which the synchronization packet that is sent from the first communication control device through the relay device is received, or a point in time at which the received synchronization packet is transmitted to the other communication device, and from the first point-in-time information that is assigned by the point-in-time assignment unit, and a communication relay updating unit that assigns the obtained information relating to the communication delay to a packet that is transmitted to the other communication device. a first communication control device; and a second communication control device that makes a connection to the first communication control device through a relay device, wherein the first and second communication control devices are provided between communication devices that perform point-in-time synchronization using a synchronization packet, wherein the first communication control device has a point-in-time assignment unit that assigns first point-in-time information relating to a point in time at which the synchronization packet that is sent from one of the communication devices is received, or a point in time at which the received synchronization packet is transmitted to the relay device, to a packet that is transmitted to the relay device, and wherein the second communication control device includes a communication delay computation unit that, for the synchronization packet, obtains information relating to a communication delay between the first and second communication control devices from second point-in-time information relating to a point in time at which the synchronization packet that is sent from the first communication control device through the relay device is received, or a point in time at which the received synchronization packet is transmitted to the other communication device, and from the first point-in-time information that is assigned by the point-in-time assignment unit, and a communication relay updating unit that assigns the obtained information relating to the communication delay to a packet that is transmitted to the other communication device.