MSDN has removed a portion of its older content dealing with enterprise architecture and application architecture. Much of this content contained information and advice that was valid for its time, but has been superceded by new techniques brought about through the introduction of the .NET Framework, the rise of pattern-based architecture, and the more stringent security requirements that underlie the Microsoft Trustworthy Computing initiative. For the most up-to-date architectural guidance, explore the Enterprise Development section of the MSDN Library and go to the .NET Architecture Center.