The outbound SYN packet from each host creates the necessary NAT state for its own NATs.
从各自的主机外出的SYN包，为他们自己的NAT产生可能的NAT状态。
NAT would do network address translation for outbound packet so that inside hosts can use reserved IP addresses and outside hosts can not visit inside ones directly to realize one-way communication.
NAT对内网主机的出网数据包进行网络地址变换，内网主机可以使用保留地址上网，外网主机无法直接访问内网主机，从而实现单向通信。
Port prediction allows a host to guess the NAT mapping for a connection before sending the outbound SYN and is discussed in detail later.
端口预报允许一个主机去猜测NAT映射，找到一个在发出外发的SYN包的连接，这个在之后还会讨论到。
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