This is to provide a defense mechanism against syn flood attacks and split handshake attack.
Enforce TCP Sequence numbers
Enforces the TCP sequence numbers for all packets.
Enforce TCP Handshake Before Allowing Data
Prevents data from passing between two clients until the three-way TCP handshake has been performed. This option should be disabled when you have mobile clients on the network as enabling this option will cause mobility to fail. You can enable this option if there are no mobile clients on the network.
Default: Disabled
Why are you trying to enable this option ?
If you are planning to , I suggest you open a TAC case and an Aruba Engineer should assist you with these settings