mtu is the network transmission maximum packet. mss is the maximum value of network transmission data. mss plus packet header data is equal to mtu. mss plus packet header data is equal to mtu. Simply take the TCP packet as an example. The message transmission 1400 bytes of data, then mss is 1400, plus 20 bytes of IP packet header, 20 bytes of tcp packet header, then mtu is 1400 + 20 + 20. Of course, when the transmission of other protocols have to add some of the packet header in the front, in short, mtu is the total of the last sent out of the size of the message. mss is that you need to send out the data size. 1. MSS: Maxitum Segment Size Maximum Segment Size 2. MSS stands for Maximum Transmission Size and is a concept within the TCP protocol. 3. MSS is the maximum data segment that a TCP packet can transmit each time. In order to achieve optimal transmission performance TCP protocol in the establishment of the connection is usually negotiated between the two sides of the MSS value, the value of the TCP protocol in the realization of the MTU value is often used instead of (need to subtract the size of the header of the IP packet 20Bytes and the header of the TCP data segment of 20Bytes), so often the MSS is 1460. communication between the two sides will be based on both sides to provide the value of the MSS The minimum value is determined as the maximum MSS value for this connection.