Listing all the differences between IIS 4 and IIS 6 would require more space than we have in this book?even if we exclude the underlying operating system changes. Of course, a lot of this book is just as applicable to IIS 4 migrations as it is to IIS 5 migrations.
IIS 4 itself was part of the Windows NT 4.0 Option Pack?this was an additional install that added a number of new features to the existing NT 4.0 platform. The primary use of the Option Pack by most people was to upgrade the fairly basic IIS 3 installation to IIS 4.
In fact, IIS development pretty much halted after IIS 4 was released, and even IIS 5 didn't add that many new features to the system. As such, there are really only a few fundamental differences between IIS 4 and IIS 6, and they are the same as those between IIS 5 and IIS 6. It's actually the other components?for example, the extension of management systems and the changes to the IIS management console component?that have any significant effect.
The biggest difference is obviously the execution environment; something we covered heavily in Chapter 2, "Architecture and Execution." IIS 4 worked with a single process, Inetsrv.exe, which handled the listening and the processing of individual requests.
IIS 6 now separates this into two components?the kernel-side HTTP.sys for listening for connections and the worker processes for actually processing individual requests.
This leads to a number of differences that you need to think about?first, the way that you currently manage your system applications, and how you manage your system performance.
Between IIS 4 and IIS 5, a new type of application pool was created; the Pooled Process enabled a number of applications to be executed within the same shared process space separate from the In Process space of the main Inetsrv.exe application.
With IIS 6, the separation of the connection manager and the processing systems allows you to individually control the two components. This changes the way you manage the server and improves the reliability and the availability of the server.
IIS 6 has extended the number of services supported by the core IIS component. IIS 4 supported only Web (HTTP), Usenet News (NNTP), and FTP services, as well as a minor SMTP forwarding service for handling the distribution of mail from Web forms. IIS 6 now incorporates mail (SMTP) and mailbox (POP3) services, as well.
If you are migrating an existing platform to IIS 6, this shouldn't cause any problems because your existing sites will be migrated as normal. However, you might want to review any additional support services, especially mail servers, in case you can merge existing services.
There are some minor differences between the earlier versions of FrontPage and FrontPage 2003 that might break certain elements of the FrontPage code and extensions you are using.
If you are using FrontPage to provide client-based page and site updates, you might want to make use of the WebDAV, which allows users to write HTML straight to the site, either from FrontPage or from other tools such as Word and Excel.
IIS 4 was the first to make extensive use of the Microsoft Management Console (MMC) to provide support for the management interface to the IIS system. You can see an example of this in action in Figure 7.1.
The Internet Service Manager, which would have been installed within the Windows NT 4.0 Option Pack and Microsoft Internet Information Server folders within the Start Menu, is now called IIS Manager and is part of the main Administrative Tools folder.
For more information on IIS and the MMC, go to the Delta Guide series Web site at www.deltaguideseries.com and enter article ID# A020701.
In essence, not much has changed in the MMC console, beyond the obvious, but what has expanded is the amount of configurable elements that are controlled directly from within the IIS Manager snap-in to MMC. For example, Web service extensions are directly controlled through the IIS manager.
Also, when working in Worker Process Isolation mode, applications are assigned according to their application pool, and application pools are separately configured within IIS Manager.
IIS 4 provided some basic integration between the Windows NT domain and IIS, enabling Windows domain authentication to use the Windows NT Domain information. IIS 6 extends the integration to the replacement for Windows NT domains?the Active Directory.
Now, virtually all elements of IIS that require a username are capable of using the Active Directory information.
IIS 6 also incorporates a feature that is part of IIS 5?the capability to automatically authenticate users logged in to an Active Directory domain on their machine to automatically be authenticated and be granted access to directories and applications.
The integration also means that the system is more secure, because data can be secured more effectively through the Active Directory system.
IIS 6 also supports Microsoft Passport authentication. However, that's not something you can just turn on, like Windows integrated authentication. It requires yearly fees to Microsoft, additional Web development work, and so forth. Stick with the other levels of authentication for most Web sites.