It is known that any network can only transmit data packet size equal to (or less than) MTU allowed in the network. If that is the case, and if we have a Path MTU discovery in place, why is there is need for MSS in TCP layer. Why does it not simply discover path MTU and set it to MSS, as after all that is what can really be transmitted at once ?
Setting MSS different (read larger) than MTU, will only burden Network Layer with fragmentation overhead.
Is there any significant advantage of using MSS ?