Method for determining NAT traversal policy and device

A method for determining a network address translation (NAT) traversal policy, wherein the method is applied to a communication system comprising a first terminal device and a second terminal device, the first terminal device accesses a network by using a first NAT device, the second terminal device accesses the network by using a second NAT device, and the method comprises:

• obtaining a first NAT message, wherein the first NAT message indicates a NAT type of the first terminal device and an Internet protocol IP address of the first terminal device in the network;
• obtaining a second NAT message, wherein the second NAT message indicates a NAT type of the second terminal device and an IP address of the second terminal device in the network;
• determining, based on the first NAT message and the second NAT message, that both the NAT type of the first terminal device and the NAT type of the second terminal device are symmetric NAT;
• determining, based on the first NAT message and the second NAT message, whether the IP address of the first terminal device in the network is the same as the IP address of the second terminal device in the network;
• and
• in a case in which the IP address of the first terminal device in the network is the same as the IP address of the second terminal device in the network, determining that the first terminal device adopts a second traversal policy to perform NAT traversal;
• wherein the first NAT message further indicates a port of the first terminal device in the network, the second NAT message further indicates a port of the second terminal device in the network, and the parameter of the second traversal policy comprises a quantity of sending rounds of detection packets, a sending sequence of detection packets in each round, a sending quantity of the detection packets in each round, a destination port step of the detection packets in each round, initial values of destination ports of the detection packets in each round, and a destination IP address of the detection packets in each round, wherein
• the sending sequence of the detection packets in each round is sending first or sending later;
• the destination port step of the detection packets in each round is a change value of a destination port of an (i+1)th detection packet in each round relative to a destination port of an ith detection packet in each round, wherein i is a positive integer;
• the initial values of the destination ports of the detection packets in each round are the port that is of the second terminal device in the network and that is indicated by the second NAT message;
• and
• the destination IP address of the detection packets in each round is the IP address that is of the second terminal device in the network and that is indicated by the second NAT message.

A communication apparatus, wherein the communication apparatus comprises a processor and a memory, the memory is configured to store computer-readable instructions, and the processor is configured to execute the computer-readable instructions to implement:

• obtaining a first network address translation (NAT) message, wherein the first NAT message indicates a NAT type of a first terminal device and an Internet protocol IP address of the first terminal device in the network;
• obtaining a second NAT message, wherein the second NAT message indicates a NAT type of a second terminal device and an IP address of the second terminal device in the network;
• determining, based on the first NAT message and the second NAT message, that both the NAT type of the first terminal device and the NAT type of the second terminal device are symmetric NAT;
• determining, based on the first NAT message and the second NAT message, whether the IP address of the first terminal device in the network is the same as the IP address of the second terminal device in the network;
• and
• in a case in which the IP address of the first terminal device in the network is different from the IP address of the second terminal device in the network, determining that the first terminal device adopts a first traversal policy to perform NAT traversal;
• wherein the first NAT message further indicates a port of the first terminal device in the network, the second NAT message further indicates a port of the second terminal device in the network, and the parameter of the first traversal policy comprises a sending sequence of detection packets in each round, a quantity of sending rounds of detection packets, a sending quantity of the detection packets in each round, a destination port step of the detection packets in each round, initial values of destination ports of the detection packets in each round, and a destination IP address of the detection packets in each round, wherein
• the destination port step of the detection packets in each round is a change value of a destination port of an (i+1)th detection packet in each round relative to a destination port of an ith detection packet in each round, wherein i is a positive integer;
• the initial values of the destination ports of the detection packets in each round are the port that is of the second terminal device in the network and that is indicated by the second NAT message;
• and
• the destination IP address of the detection packets in each round is the IP address that is of the second terminal device in the network and that is indicated by the second NAT message.