 rolandeCertifiablePremium,Mod
join:2002-05-24
Columbus, OH
Linksys
AT&T Midwest
| reply to tham121988
Re: Not getting full 12mbsFYI Windows 7, as well as Vista, by default enables the "Autotuning" feature on the TCP stack which enables the Window Scaling option defined in RFC 1323 to be dynamically calculated based on your bandwidth/delay product. Many webservers, load balancers, and firewalls are not fully compliant or not supporting Window scaling as it becomes more aggressive. The dynamic portion of this control was more conservative in Vista which helped in most cases. However, it appears to have gotten more aggressive in Windows 7 thus leading to more complaints and problems that are not easy to identify or diagnose. Believe me, I have seen my share just in the past few months and spent many hours debugging the issues.
I have personally witnessed several instances where this lovely new default feature actually causes a small window to be negotiated between the client and the server because the server or device in between ignores the window scale factor and thus results in very poor throughput. Of course, the higher the latency between the client and server, this problem becomes exponentially more pronounced. Unfortunately, on average, this new capability doesn't seem to play nicely on the Internet if it is too aggressive. Disabling Autotuning so the stack acts like the long supported behavior or possibly setting it to restricted mode could possibly resolve throughput problems, depending on the webserver or application you are using.
netsh interface tcp set global autotuninglevel=disabled
netsh interface tcp set global autotuninglevel=restricted
To return to the default setting:
netsh interface tcp set global autotuninglevel=normal
You can view the settings on your PC with the following command:
netsh interface tcp show global
--
Scott, CCIE #14618 Routing & Switching
Too bad those that know it all can't do it all.
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