As Mac OS X is mainly a BSD derivative, you can use similar mechanisms to tune the TCP stack - see under BSD OS Specific
See the End System Tcp Buffer Sizing topic for general information about sizing TCP buffers.
For testing temporary improvements, you can directly use
sysctl in a terminal window: (you have to be root to do that)
sysctl -w kern.ipc.maxsockbuf=8388608 sysctl -w net.inet.tcp.rfc1323=1 sysctl -w net.inet.tcp.sendspace=1048576 sysctl -w net.inet.tcp.recvspace=1048576 sysctl -w kern.maxfiles=65536 sysctl -w net.inet.udp.recvspace=147456 sysctl -w net.inet.udp.maxdgram=57344 sysctl -w net.local.stream.recvspace=65535 sysctl -w net.local.stream.sendspace=65535
For permanent changes that last over a reboot, insert the appropriate configurations into Ltt>/etc/sysctl.conf. If this file does not exist must create it. So, for the above, just add the following lines to sysctl.conf:
kern.ipc.maxsockbuf=8388608 net.inet.tcp.rfc1323=1 net.inet.tcp.sendspace=1048576 net.inet.tcp.recvspace=1048576 kern.maxfiles=65536 net.inet.udp.recvspace=147456 net.inet.udp.maxdgram=57344 net.local.stream.recvspace=65535 net.local.stream.sendspace=65535
Note This only works for OSX 10.3 or later! For earlier versions you need to use /etc/rc where you can enter whole sysctl commands.
Users that are unfamiliar with terminal windows can also use the GUI tool "TinkerTool System" and use its Network Tuning option to set the TCP buffers.
TinkerTool System is available from:
-- ChrisWelti - 30 Jun 2005