You can adjust the TCP maximum segment size (MSS) to improve the throughput for the TCP session over a Fabric Extend (FE) adjacency.
When a client initiates a connection with a server, it uses TCP SYN packets to negotiate the MSS to avoid fragmentation. The client and server use the outgoing maximum transmission unit (MTU) to advertise the MSS.
If a tunnel exists between the client and server, the encapsulation consumes more room in the outer IP header. As a result, the router that performs the tunnel encapsulation fragments the packet to fit over the tunnel. Adjust the MSS to modify the value in the TCP SYN packet so the client and server negotiate a lower number and leave headroom for tunnel encapsulation.
This adjustment functionality applies to IPv4 only.
Important
If you enable this functionality and port mirroring simultaneously, the switch does not mirror CP-generated packets.
TCP MSS adjustment applies unidirectionally when a packet is forwarded from a UNI interface to any other interface. To use this functionality, you must enable TCP MSS adjustment on both sides of the FE tunnel.