Because Darwin is BSD-based, it's no surprise that Mac OS X TCP Performance Tuning is very similar to FreeBSD TCP Performance Tuning. Although RFC 1323 TCP Extensions should be enabled by default, it doesn't hurt to force them on. Also, we'll set the TCP send and receive window sizes to 1 MB.

Mac OS X does not include /etc/sysctl.conf, so you'll need to create it. Once that's done, add the following lines and reboot.

net.inet.tcp.rfc1323=1
kern.ipc.maxsockbuf=16777216
net.inet.tcp.sendspace=1048576
net.inet.tcp.recvspace=1048576

You can avoid rebooting by issuing the following commands: (As always, the '$' represents the shell prompt and should not be typed.)

$ sudo sysctl -w net.inet.tcp.rfc1323=1
$ sudo sysctl -w kern.ipc.maxsockbuf=16777216
$ sudo sysctl -w net.inet.tcp.sendspace=1048576
$ sudo sysctl -w net.inet.tcp.recvspace=1048576

Unlike FreeBSD, Mac OS X has plenty of network memory buffers (mbufs) by default.