Communication device, communication method, integrated circuit, and program

A communication method performed by a communication device which communicates with a server device connected to the Internet, via (i) an upper layer Network Address Translation (NAT) device connected to the Internet and (ii) a lower layer NAT device connected to the upper layer NAT device, said communication method comprising:

• collecting information indicating a Local Area Network (LAN)-side Internet Protocol (IP) address of the upper layer NAT device and information indicating a Wide Area Network (WAN)-side IP address of the lower layer NAT device;
• issuing a port mapping command for the lower layer NAT device to transfer a packet to the communication device, the packet arriving at a predetermined port number of the lower layer NAT device;
• generating a determination packet which is source-routed, said generating includes:
• determining, as a relay destination of the determination packet, the LAN-side IP address of the upper layer NAT device collected in said collecting;
• determining, as a final destination of the determination packet, the WAN-side IP address of the lower layer NAT device collected in said collecting;
• and
• determining, as a destination port number of the determination packet, a same port number as the predetermined port number used for the port mapping command;
• transmitting the determination packet which is generated in said generating;
• receiving the determination packet which is transmitted from the determination packet transmitting unit, passes through the upper layer NAT device and the lower layer NAT device, and arrives at the communication device;
• and
• obtaining a port number of the lower layer NAT device which is a source port number indicated in the determination packet received in said receiving.

A program recorded on a non-transitory computer-readable recording medium for communicating with a server device connected to the Internet, via (i) an upper layer Network Address Translation (NAT) device connected to the Internet and (ii) a lower layer NAT device connected to the upper layer NAT device, said program comprising:

• collecting information indicating a Local Area Network (LAN)-side Internet Protocol (IP) address of the upper layer NAT device and information indicating a Wide Area Network (WAN)-side IP address of the lower layer NAT device;
• issuing a port mapping command for the lower layer NAT device to transfer a packet to said communication device, the packet arriving at a predetermined port number of the lower layer NAT device;
• generating a determination packet which is source-routed, said generating includes:
• determining, as a relay destination of the determination packet, the LAN-side IP address of the upper layer NAT device collected in said collecting;
• determining, as a final destination of the determination packet, the WAN-side IP address of the lower layer NAT device collected in said collecting;
• and
• determining, as a destination port number of the determination packet, a same port number as the predetermined port number used for the port mapping command;
• transmitting the determination packet which is generated in said generating;
• receiving the determination packet which is transmitted in said transmitting, passes through the upper layer NAT device and the lower layer NAT device, and arrives at the communication device;
• and
• obtaining a port number of the lower layer NAT device which is a source port number indicated in the determination packet received in said receiving.

An integrated circuit which communicates with a server device connected to the Internet, (i) via an upper layer Network Address Translation (NAT) device connected to the Internet and (ii) a lower layer NAT device connected to the upper layer NAT device, said integrated circuit comprising:

• a connection environment check unit configured to collect information indicating a (Local Area Network) LAN-side Internet Protocol (IP) address of the upper layer NAT device and information indicating a Wide Area Network (WAN)-side IP address of the lower layer NAT device;
• a determination purpose port mapping command unit configured to issue a port mapping command for the lower layer NAT device to transfer a packet to said communication device, the packet arriving at a predetermined port number of the lower layer NAT device;
• a determination packet generation unit configured to generate a determination packet which is source-routed, said determination packet generation unit includes:
• a relay destination determination unit configured to determine, as a relay destination of the determination packet, the LAN-side IP address of the upper layer NAT device collected by said connection environment check unit;
• a final destination determination unit configured to determine, as a final destination of the determination packet, the WAN-side IP address of the lower layer NAT device collected by said connection environment check unit;
• and
• a destination port determination unit configured to determine, as a destination port number of the determination packet, a same port number as the predetermined port number used for the port mapping command;
• a determination packet transmitting unit configured to transmit the determination packet which is generated by said determination packet generation unit;
• a determination packet receiving unit configured to receive the determination packet which is transmitted from said determination packet transmitting unit, passes through the upper layer NAT device and the lower layer NAT device, and arrives at the communication device;
• and
• a port number obtainment unit configured to obtain a WAN-side port number of the lower layer NAT device which is a source port number indicated in the determination packet received by said determination packet receiving unit.