The idea is trivial in that a client and server connection on a local loopback interface within the same system should not need the entire TCP/IP protocol stack to exchange data.
Therefore, provide a faster data path with the fusion of the two end points.
The fusion of two local TCP endpoints occurs at connection establishment time.
tcp_fuse_output() enqueues application data directly onto the peer's receive queue; no protocol processing is involved.
Flow control information is manipulated outside the squeue, so the tcp_non_sq_lock must be held when touching tcp_flow_stopped.The feature may be enabled or disabled via the /etc/system config file for the Solaris or genunix kernel and the only line required is "set ip:do_tcp_fusion = 0x0" which set the feature off or FALSE while of "0x1" for hexadecimal TRUE.