When a TCP segment is received, the TCP router knows which port to pass it to by looking at the port number in the TCP header.

当接收到一个tcp段时，tcp路由器通过查看tcp报头中的端口号就知道向哪个端口传送包。

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As discussed above, when Host a wants to establish a TCP connection to destination Host d, it sends a TCP segment with the SYN flag set first.

如上所述，当主机A想建立到目的地主机d的TCP连接时，它首先发送设置了SYN标志的tcp段。

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Using this method, you can at least know (or guess, rather) what TCP segment sizes are likely to be passed through without getting fragmented at the IP level.

使用这种方法，您至少可以了解(或者猜测)在不对ip层进行分片的情况下可能通过的tcp报文段的大小。

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