摘自《TCP/IPIllustrated,Volume1TheProtocols》17.TCP:传输控制协议(protocol)Theheaderlengthgivesthelengthoftheheaderin32-bitwords.Thisisrequiredbecausethelengthoftheoptionsfieldisvariable.Witha4-bitfield,TCPislimitedtoa60-byteheader.Withoutoptions,however,thenormalsizeis20bytes.为什么TCP限制为60字节的hader？在我看来1)hea