Mac OS X and Linux TCP Window Scaling

The Ohio State University at Lima
Technical Bulletin #200711011550

Recent updates pushed from Apple and Linux distributions may enable TCP window scaling, or RFC 1323 compatibility.  This is the same problem that Vista has after installation, and it manifests itself by websites not opening or timing out, or other network functions responding very slowly or not at all.

Warning:  Changing these settings requires administrative access (root-level) and serious damage could occur!  Use at your own risk, or seek assistance from your IT Help Desk!

Mac OS X, in a Terminal window: sudo sysctl -w net.inet.tcp.rfc1323=0 for current session.

To make it permanent:

(as root or sudo, in a Terminal window) edit or create a file in /etc called sysctl.conf and add the following:  net.inet.tcp.rfc1323=0

Or a one-liner, again in a Terminal window: sudo echo "net.inet.tcp.rfc1323=0" > /etc/sysctl.conf

And reboot.  Make sure to enter the line exactly as shown-don’t add any whitespace around the equals sign!

Linux:  (as root or sudo, in a Terminal window or shell session)

echo 0 > /proc/sys/net/ipv4/tcp_window_scaling

To make it permanent:

(as root or sudo, again in terminal or shell window) edit /etc/sysctl.conf, locate (or create) entry for net.ipv4.tcp_window_scaling and change from 1 to 0, entry should read:

net.ipv4.tcp_window_scaling=0

and reboot.