Bad Tweak – Disable Receive Window Auto-Tuning

A reader just commented on this so this is a quickie article to debunk this “tweak”.

The “tweak”
-set autotuninglevel=disabled
-default setting = netsh int tcp set global autotuninglevel=normal
-to check your setting Open Admin Command Prompt and enter netsh interface tcp show global
-disabled = Open Admin Command Prompt and enter netsh int tcp set global autotuninglevel=disabled
-return to default = Open Admin Command Prompt and enter netsh int tcp set global autotuninglevel=normal
-This setting does not require a reboot.

Explanation
Receive Window Auto-Tuning popped up with Windows Vista and has been a feature of every Windows version since.
I’m going to try and explain this in a VERY oversimplified manner for the non-technical among us. If you want a good full breakdown see: The Cable Guy TCP Receive Window Auto-Tuning
Over the internet your info flows through a pipe. It does so in bunches at a time called packets. Think of it as a ball rolling through the pipe. The pipe may not be perfectly round and may change size and shape between you and your end connection be that a website or whatever.
Back in the day all OS’s used to just set the size of a packet of info and shove it into the pipe. That could either have the size of the packet needlessly small or so large it would jam up the pipe trying to squeeze itself through. Also, often the two connected computers often can send/receive data at different rates, sending too fast could lead to dropped packets (info not getting there). With every packet sent the sending computer would say “did you get that?” and the receiving computer wold say yes or no. If no the packet gets resent. This is called ACK. Obviously all this increases network traffic.
That led to Geeks tinkering with the receive window settings (RWIN) to try and max out their personal connection. It worked to some degree but not with every connection. Often the optimal setting for one connection was less than optimal for another. Then some Geeks figured out how to make the process “smart”. Your computer and the one your connected to (say, a website) now quickly figure out the maximum size of a packet that can be sent and how fast to send it.
So you see, in the vast majority of cases (like 99.999%) Receive Window Auto-Tuning is a good thing.
I hope that made sense.

What Microsoft Says
Microsoft Windows Networking Team – An Update on Windows TCP AutoTuningLevel

Like all modern operating systems Windows has receive window auto-tuning to dynamically adjust the receive buffer size to the throughput and latency of the link. Disabling this feature will definitely limit your Internet speeds. Auto-tuning is consistent throughout all variants of TCP and present in all modern operating systems. In the modern Internet the range of latencies and throughput speeds that must be accommodated is simply too large to manage statically and must be adjusted dynamically. If you have changed your AutoTuningLevel to disabled, please reset it to normal in order to restore your Internet speeds…Auto-Tuning on the other hand should NEVER be disabled.

My Tests
Test Machine = Windows 10 Pro 64-bit
RED = Slower

*Note – The slower speeds were retested several times with similar results.

Conclusion
In my tests his setting seems to have either no effect or a negative effect.
BAD TWEAK