This is the second part in understanding the IIS version 7.0

1. “Understanding our IIS - Part2”

2. IIS 6.0 Isolation Mode

3. Why IIS7.0 ?
• Http.Sys – listens HTTP request but we need
more Protocol Listeners for WCF services
• WWW Publishing Service = Dividing Roles b/w
WWW service + Windows Process Activation Service
(WAS)
• Instead of keeping the majority of functionality
within the server itself, IIS include a Web server
engine in which you can add or remove
components, called modules, depending on your
needs.
• Security & Simple Administration

4. IIS7.0 Components
• Kernel Mode
– HTTP.sys
• User Mode
– WWW Service
– Windows Process Activation Service(WAS)
– Modules (Native & managed)
– Application Pools (Integrated & Classic)
Request Processing in IIS7.0

5. Remember This

6. HTTP.sys
• Also known as “HTTP Protocol Stack” or “Http
Listener Process”
• Implemented as a kernel-mode device driver
• Core component to receive and serve HTTP
requests and passing them off to the worker
processes
• When you create a Web site, IIS registers the site
with HTTP.sys
• Other than retrieving a stored response from its
internal cache, HTTP.sys does not process the
requests that it receives.
• Uses kernel mode request queue.

7. WWW Service
• Also known as “World Wide Web
Publishing Service” + WAS
• It manages the IIS metabase,
• It is primarily responsible for
configuring HTTP.sys, updating it when
configuration changes, and notifying
WAS when a request queues.
• Additionaly collects the counters for
Web Sites.

8. WAS

Manages app pool and worker processes.

WAS reads config info from
ApplicationHost.config and passes the
info to listener adapters on the server.

Any change in this config will be passed
to listener adapters which is a channel
b/w WAS and HTTP.sys

WAS majorly performs the WWW service
tasks.

9. Modules

Instead of keeping the majority of
functionality within the server itself, IIS
include a Web server engine in which
you can add or remove components,
called modules, depending on your
needs.

Modules are individual features that the
server uses to process requests.

Provides customization and simplifies
administration.

10. Native Modules

HTTP Modules – redirect requests,
return HTTP errors etc.

Security Modules – Authentication &
Authorization etc.

Content Modules – Setting default page,
serving static content etc.

Compression & Caching Modules

Logging & Diagnostics Modules

There are system level dlls for each of
the specific modules in IIS7.0

11. Managed Modules

In addition to native modules, IIS
enables you to use managed code
modules to extend IIS functionality.

Managed modules depend on the
ManagedEngine module.

AnonymousIdentificationModule

DefaultAuthentication

FileAuthorization/FormsAuthentication

WindowsAuthentication

12. Application Pools
• Group of Web Applications and Web Sites are
called Application Pools
• Every application within an application pool
shares the same worker process
• The worker process(w3wp.exe) that services one
application pool is separated from the worker
process that services another
• Integrated mode and Classic mode are set at the
application pool level, which enables you to run
applications simultaneously in application pools
with different process modes on the same server.

13. Integrated App Pool
Mode
When a worker process in an application
pool receives a request, the request
passes through an ordered list of events.

Each event calls the necessary native
and managed modules to process
portions of the request and to generate
the response.

The request-processing models of IIS and
ASP.NET are integrated into a unified
process model.

14. Classic App Pool Mode

When an application pool is in Classic
mode, IIS 7 and above handles requests
in the same way as in IIS 6.0 worker
process isolation mode.

This separation of the IIS and ASP.NET
request-processing models results in
duplication of some processing steps,
like authentication and authorization.

Managed code features, such as Forms
authentication, are only available to
ASP.NET applications (aspnet_isapi.dll)

15. Again Remember This

16. Request Processing

When a client browser initiates an HTTP
request for a resource on the Web
server, HTTP.sys intercepts the request.

HTTP.sys contacts WAS to obtain
information from the config. store.

WAS requests config. info from the
applicationHost.config.

WWW Service receives config info, such
as application pool and site
configuration.

17. Request Processing

WWW Service uses the configuration
information to configure HTTP.sys.

WAS starts a worker process for the
application pool to which the request
was made.

The worker process processes the
request and returns a response to
HTTP.sys.

The client receives a response.