Application Scenarios for PCP
This section describes the application scenario of PCP.
As shown in Figure 1, P2P services run in the NAT444 scenario, and the FW acts as the CGN and supports the PCP server function. The IPv4 private network user obtains a public IP address and a public port number from the CGN through the CPE and then uses the public IP address to access the Internet. The Internet user can proactively communicate with the IPv4 private network user through the CGN that has the PCP mapping table. In this way, P2P services can properly run, and user experience in the P2P services is improved.
