Any tools to tweak the TCP/IP stack?
 

Are there any good tools out there to tweak the TCP/IP stack for optimal performance on Linux?

I know Windows has a tool called TCPOptimizer that can tweak the TCP/IP stack, but is there anything like this for Linux or even Slackware?

You will need to do some research into the kernel settings. They can be done using sysctl. you find most of them are set in /proc. you will configure /etc/sysctl.conf for the settings to remain persistent through reboots.

Some pointers like this and that. But that's one side of tuning; the other is making sure that your network applications can send and receive data in large TCP buffer windows (when applicable,) such as tunables in Samba or NFS.

As noted in the latter URL, modern 2.6 kernels do TCP autotuning, which should be fine for most tasks; if you're tuning for a WAN, however, be sure to do it on the gateway, as you don't (usually) need it within a LAN.