Mar 29, 2010 Windows Vista/7 has the ability to automatically change its own TCP Window auto-tuning behavior to a more conservative state regardless of any user settings. It is possible for Windows to override the autotuninlevel even after an user sets their custom TCP auto-tuning level. In Windows Vista, Windows Server 2008, and later versions of Windows, the TCP Receive Window size is negotiated by a feature that is named TCP Receive Window Auto-Tuning Level. This feature can negotiate a defined Receive Window size for every TCP communication during the TCP Handshake. Windows (Vista/7/8/etc) will automatically set - and more importantly, increase - the size of the TCP receive window for you, as needed, to maximize throughput. Receive Window Auto-Tuning: Microsoft calls this automatic management of the receive window size 'auto-tuning'. TCP Window Auto Tuning This setting tunes the TCP Receive Window auto-tuning algorithm in Windows. A small TCP Receive Window can limit high-speed, high-latency transfers, such as most broadband internet connections.
I am uncertain about the more modern Windows OS like 8.1 and Server 2012. However, auto-tuning did not work correctly in Windows 7 and Server 2008 R2. One of the biggest symptoms was that GUI-based copy/paste between Windows 7 workstations and Server 2008 R2 servers would fail or creep along very slowly (think of copying a file to the company share or your home drive). Disabling auto-tuning, receive-side scaling, and heuristics almost eliminated the issue for me. If your environment consists of these particular operating systems, then you will want to disable auto-tuning, receive side scaling, and heuristics on both the workstations and servers. There is a hotfix but it may be just as easy to either script it or do it manually.
It is an easy fix and won't interrupt production.
Windows 2012 Tcp Auto Tuning Download
Windows Auto Tuning
EDIT: Has to be done with elevated privileges.