Configuring an Application Isolation Mode

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Applies To: Windows Server 2003, Windows Server 2003 with SP1

So that you can match the needs of your server configuration to the requirements of your applications, and to provide more flexibility if you are upgrading from an earlier version of IIS, IIS 6.0 offers an adjustable architecture for isolating your applications. IIS 6.0 can run an application server in one of two process models, called application isolation modes:

  • Worker process isolation mode, which is the default application isolation mode for IIS 6.0, isolates key components of the World Wide Web Publishing Service (WWW service) from the effects of defective applications and protects applications from each other by using isolated worker processes.

  • IIS 5.0 isolation mode, which processes requests in nearly the same way that IIS 5.0 does, is provided for applications that depend on specific features and behaviors of IIS 5.0 or earlier. Use this isolation mode only if an application has a compatibility problem, which you cannot resolve, when it runs in worker process isolation mode.

Both application isolation modes use the HTTP protocol stack, HTTP.sys, in almost identical ways. The primary difference is that in worker process isolation mode, HTTP.sys can route requests to multiple queues; in IIS 5.0 isolation mode, HTTP.sys routes requests to a single queue. For more information about IIS 6.0 request processing, see IIS 6.0 Architecture.