autotuninglevel tcp

• Open a command prompt and execute the following command:

netsh int tcp set global autotuninglevel=disabled
The default level is "normal." The possible settings include:

• disabled: uses a fixed value for the tcp receive window. Limits it to 64KB (limited at 65535).
• highlyrestricted: allows the receive window to grow beyond its default value, very conservatively
• restricted: somewhat restricted growth of the tcp receive window beyond its default value
• normal: default value, allows the receive window to grow to accommodate most conditions
• experimental: allows the receive window to grow to accommodate extreme scenarios (not recommended as it can degrade performance in common scenarios; only intended for research purposes. It enables RWIN values of over 16 MB)

http://kb.globalscape.com/KnowledgebaseArticle10438.aspx