what is the difference between "firewall tcp-mss" and "tcp max-mss"?

Hey there!

Run the 'tcp max-mss' command to configure the maximum MSS.

 
The MSS advertised by the local end is min (interface MTU – 40, MSS configured on the local end). If PPPoE is used for setting up an uplink, the MSS advertised by the local end is min (interface MTU – 48, MSS configured on the local end).
The negotiated MSS is min (interface MTU – 40, MSS configured on the local end, MSS advertised by the remote end). If PPPoE is used for setting up an uplink, the negotiated MSS is min (interface MTU – 48, MSS configured on the local end, MSS advertised by the remote end).

If the negotiated MSS is less than or equal to the configured minimum MSS value, the minimum MSS value takes effect to prevent DDoS attacks caused by overly small MSS values.

If the negotiated MSS is greater than or equal to the configured maximum MSS value, the maximum MSS value takes effect. Otherwise, TCP packets may be larger than the MTU and therefore discarded.

For more information, please refer to this link: http://support.huawei.com/hedex/ ... ributes&lang=en.