说明：  因为当前 IPV4地址的缺乏 ,nat、防火墙的中介设备和不对称寻址建立起来的 p2p通信机制造成了地址访问的问题。 在 internet最初体系结构中，每个节点都有全球唯一的 ip地址，能够直接通信。可是随着节点的增多， ip地址使用紧张，他们需要中介设备如 nat连在一起。
(Because of the current IPV4 address the lack of, nat firewall intermediary device and asymmetric the addressable set up peer-to-peer communication mechanism causing the address access issues. In the the internet initial architecture, each node has a unique ip address in the world, able to communicate directly. However, with the increase in the node, ip address using the tension, they need an intermediary device such as nat together.)