When a TCPsegment 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。
2
As discussed above, when Host a wants to establish a TCP connection to destination Host d, it sends a TCPsegment 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。
3
Using this method, you can at least know (or guess, rather) what TCPsegment sizes are likely to be passed through without getting fragmented at the IP level.