Internet Information Services
IIS (Microsoft Internet Information Services,) is the web server integrated with Windows servers (such as Windows NT, Windows 2000, and Windows Server 2003.) The current (Windows 2003) version is IIS 6. FTP, SMTP, and HTTP servers and packaged in the bundle.
Features
This web server implements the embrace, extend, extinguish policy by adding proprietary features such as Active Server Pages, FrontPage Extensions, and ASP.NET. IIS will work with PHP although quite a number of modifications are needed to unite PHP and IIS to work together, and as such it's likely that other user-installed extensions may work as well. HTTPS capability is integrated with Certificate Services.
Compatibility
Internet Information Services was designed to run on a Windows professional or server operating system, but a workaround for Windows XP Home Edition was (accidentally) posted on Microsoft's Knowledge Base. Management quickly deleted the article.
Uptime
Microsoft commissioned a firm to evaluate the TCO (Total Cost of Ownership) of Windows 2000 (see the Windows Server 2003 article.) In the survey of IT professionals, Linux had a higher uptime percentage than Windows, because (according to the survey,) more Linux servers were deployed than Windows servers. (High licensing costs probably led IT departments to purchase fewer servers, although that problem may be fixed with the release of Windows Server 2003 Web Edition.)
Competitors
Naturally, Linux/Apache would come to mind as competing for web server markets, but for enterprises, Solaris Operating Environment/J2EE might be a better match. Java 2 Platform, Enterprise Edition is Sun Microsystems enterprise framework comparable to Microsoft's .NET. Most Fortune 500 companies use Java for their enterprise back-end, which also has high licensing costs.