Urgent::::::How to access 3 layers from three different servers in asp.net,c#

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C++

ASP.NET4

Hi,
I have a question.
for example:
1.we have 3 layers ie business,data access and ui layes and all these three layers are residing in three different server.
My question is How to access these layes or merge these layes so that it works success fully? in asp .net with c#.

2.how to restricted unauthorized users to access the page.
ie suppose we have 2 pages --login and registration.
i want if i type registration page url it should not be accessed with out login.
if i try to login then return back to login page and ask for login. how to do it?

please send me the solution as soon as possible in below mail id
xxx@xxx.com (Mail removed by editor)

Thanks in advance.