如果你是使用MSDN与Microsoft Visual Studio Ultimate 2010版本，然后您不需要为任何数量的虚拟用户购买许可证与控制器&代理商设置。

If you are using MSDN with Microsoft Visual Studio Ultimate 2010 edition, then you don't need to purchase license for any number of virtual Users with controller & agents settings.

一旦通过 链接：

Once go through  links:

http://blogs.msdn.com/b/edglas/archive/2009/ 10/20 / introduction-the-microsoft-visual-studio-load-test-virtual-user-pack-2010.aspx

http://blogs.msdn.com/b/edglas/archive/2009/10/20/introducing-the-microsoft-visual-studio-load-test-virtual-user-pack-2010.aspx

http://msdn.microsoft.com/en- us / vstudio / ff520697.aspx

http://msdn.microsoft.com/en-us/vstudio/ff520697.aspx

对于你的问题（1），问题（2），问题（3），以下是答案：

For your question(1),question(2),question(3),Following is answer:

"Ip Switching"是推送"虚拟用户加载请求"的功能。来自不同代理商的各种"IP范围"和

"Ip Switching" is feature to push "virtual user load requests" from various "ip ranges"
from different agents

浏览链接：

http：// msdn .microsoft.com / zh-CN / library / ms404667（v = vs.90）.aspx

http://msdn.microsoft.com/en-us/library/ms404667(v=vs.90).aspx

http://msdn.microsoft.com/en-us/library/dd695837。 aspx

http://msdn.microsoft.com/en-us/library/dd695837.aspx

http://blogs.msdn.com/b/billbar/archive/2007/11/28/troubleshooting-the-vsts-load-testing-ip-switching-feature。 aspx

http://blogs.msdn.com/b/billbar/archive/2007/11/28/troubleshooting-the-vsts-load-testing-ip-switching-feature.aspx

我希望，你会对我的答案感到满意

I hope,you will be satisfied with my answers

如果有任何疑问，请告诉我

if any more query then let me know