Flow control method, transmitting terminal device used in same, receiving terminal device and packet transfer system

A receiving terminal that relays a packet sent from a transmitting terminal to another receiving terminal, the receiving terminal comprising:

• a measurement packet transmitting section that transmits to the another receiving terminal a packet containing measurement information for measuring a round trip time the packet takes between the receiving terminal and the another receiving terminal;
• a receiving section that receives a reply packet sent from the another receiving terminal in response to the packet containing the measurement information;
• a round trip time information acquiring section that acquires time information about the round trip time of the packet, based on the reply packet received in the receiving section;
• and
• a round trip time information transmitting section that transmits to the transmitting terminal the packet containing the time information acquired in the round trip time information acquiring section.

A transmitting terminal that delivers a packet via receiving terminals that relay the packet, the transmitting terminal comprising:

• a receiving section that receives, for each pair of terminals adjoining on a delivery route, a packet containing information about around trip time the packet takes between the each pair of terminals;
• a round trip time acquiring section that calculates the round trip time from the packet received in the receiving section;
• a selection section that selects one of round trip times calculated in the round trip time acquiring section, based on a predetermined reference;
• and
• a calculation section that calculates a transmission rate of the packet, based on the round trip time selected in the selection section.

A packet transport system that delivers a packet transmitted from a transmitting terminal by relay by a receiving terminal,

• the receiving terminal comprising:
• a measurement packet transmitting section that transmits a packet containing measurement information for measuring a round trip time the packet takes between the receiving terminal and another receiving terminal to which the packet needs to be relayed, to the another receiving terminal;
• a receiving terminal receiving section that receives a reply packet sent from the another receiving terminal in response to the packet containing the measurement information;
• a round trip time information acquiring section that acquires time information about the round trip time, based on the reply packet received in the receiving terminal receiving section;
• and
• a round trip time information transmitting section that transmits to the transmitting terminal the packet containing the time information acquired in the round trip time information acquiring section;
• and
• the transmitting terminal comprising:
• a transmitting terminal receiving section that receives the packet containing the time information from the receiving terminal;
• a round trip time acquiring section that calculates the round trip time from the packet received in the transmitting terminal receiving section;
• a selection section that selects one of round trip times calculated in the round trip time acquiring section, based on a predetermined reference;
• and
• a calculation section that calculates a transmission rate of the packet, based on the round trip time selected in the selection section.