Saturday, May 3, 2008

Vista Networking: Disable Auto-Tuning feature

(If file is taking longer time while copying over network, connection getting dropped frequently, Slow Remote desktop ,try to disable Vista’s auto tuning feature and see the difference)
Since vista's arrival on cyber earth, life of network user becomes more difficult. Suddenly there is a realization that networking in vista with other OS system is not as "evolved" as it is with other ‘races’ of operating systems. The main reasons backing such feelings are
1.Vista takes longer time to copy medium to large size files over network.
2.Large File transfer is also not as reliable as in XP networking and other OS
3. If you copy/ move big files even on the same partition, it takes long time to determine how much is data sized, how much time it will take to copy , before beginning the actual task of copying/moving. Whereas even in windows 98 , it is as quick which can be termed as “Instantaneous”.
Why this is happening with Vista? Here lies the answer

Windows Vista equipped with new feature called "Receive Window Auto-Tuning”. It constantly monitors network bandwidth for its capacity and network latency. Based on network conditions, it adjusts the TCP window size on the fly, in real time. If network condition is good it can scale up TCP windows upto whooping 16MB size or more, and if it is poor it can scale it down to default 64K size.

Because of this auto-tuning feature or changing nature of its networking component, Vista causes troubles to other network PCs in network , servers , firewall-systems, software and ultimately users. When it scale up the TCP windows size, it is not necessary that client is also " capable and ready " to accept and work with that data size determined by Vista. Many firewalls also limit the maximum size of TCP packet to prevent DoS kind of attacks. Thus vista's decision to increase in packet size well shot down by such filewalls. There are many such situations in which change in packet size by vista on the fly will not be understood by networking system and ultimately get blocked , which causes dropped connection even in local area network.

So bottomline: If you have small network with all Vista systems, connected via same switch, use this feature. Otherwise keep it disable. In production environment, better keep it disabled.
How to disable:

Log on as Administrator, open Command window and issue the following command
netsh interface tcp set global autotuninglevel=disabled
It will do rest of the job for you.
If you experience that your Remote Desktop connection is slow , type this too .
netsh interface tcp set global rss=disabled
If you have any problems, then to turn auto-tuning back on type the following in
command prompt:
netsh interface tcp set global autotuninglevel=normal
Happy Networking

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