TCP window scale option
The TCP window scale option is an option to increase the TCP congestion window size above its maximum value of 65,536 bytes. It is defined in IETF RFC 1323. The congestion window size may be increased up to a maximum value of 1 gibibyte (1,073,741,824 bytes). This is done by specifying a one byte shift count in the header options field. The true congestion window size is left shifted by the value in shift count. A maximum value of 14 may be used for the shift count value.
Compatibility problems
Windows Vista
TCP Window Scaling is widely implemented in the Windows Vista operating system. Because many routers do not properly implement TCP Window Scaling, it can cause a users Internet connection to malfunction intermittently for a few minutes, then appear to start working again for no reason. If "diagnose problem" is selected in Vista, an error message will be displayed "cannot communicate with primary DNS server." [1]
Linux
Linux kernels (from 2.6.8) have enabled TCP Window Scaling by default, which may raise potential problems in this area.
Sources
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