OWIN is a specification that decouples web applications from web servers by establishing an abstraction layer, allowing applications to run on any OWIN-compliant server. Katana is a set of components built by Microsoft using OWIN specifications, including Web API, ASP.NET Identity, and SignalR. In a Katana application, requests flow through layers - the application, middleware components, the server, and the host process manager. This allows flexibility in choosing and arranging middleware before requests reach the server.

1. OWIN And KATANA Overview

2. Introduction
With the emerging popularity of OWIN , it is important for ASP.NET
developers to understand in details OWIN and Katana . ASP.NET Web
API and ASP.NET Identity are already forwarded towards using these
specifications. This article explains what OWIN and Katana are and how
they suit the whole web development picture for ASP.NET developers.
The .NET framework came into existence in 2002. ASP.NET was
packaged as a part of the overall .NET framework. The idea was to
provide a unified development framework for creating desktop and web
applications and services. In those days Windows development tools
such as VB6 were very common . Naturally, ASP.NET and Visual Studio
attempted to provide a RAD (Rapid Application Development)
development environment to web developers.

3. OWIN
OWIN is a specification that says how web development frameworks
such as ASP.NET MVC must interact with the web servers. The goal of
OWIN is to decouple web applications from the web server by
establishing an abstraction layer.
Such an abstraction enables you to run the same application on all the
web servers that support OWIN.
Moreover it simplifies the overall system because that layer can provide
a lightweight infrastructure to provide the applications.

4. Katana
Katana is a whole set of components by Microsoft built using OWIN
specifications. Some of these components are Web API, ASP.NET
Identity and SignalR.
Overall architecture of a Katana based application
APPLICATION ——> Your application
MIDDLEWARE——-> Web API, Authentication, SignalR, etc
SERVER—————–>Listen to requests; serve the content
Host———————–> Process management; environment

5. Overall architecture of a Katana based application
The figure denotes there are four layers namely Application, Middleware, Server
and Host. Let’s illustrate the function of each of these layers.
The Application layer indicates client application. For example, a web site
developed in ASP.NET MVC. It could also be a Windows based application or a
console application. This application is used by the end users and it need not do
anything special as far as OWIN is considered.
The Middleware layer indicates a set of components built using OWIN
specifications. These constituents can be larger frameworks such as Web API or
special components such as ASP.NET Identity or SignalR. There can be more
than one constituent in this layer. If so, they can form a pipeline – a chain of
components – that is implemented before the request reaches the server. You
can add or remove the components from this chain through your code.

6. The final layer is the Host. This layer creates and manages a process
for your request. It also provides the overall atmosphere for your
application. There are three options for hosting applications based on
Katana:
IIS
OwinHost.exe
Custom host

7. The first option utilizes IIS as the host. Notice that IIS acts as a host as
well as a server. The OwnHost.exe is a ready made lightweight host that
you can use to host your applications. If these two options do not suffice
your requirements you can always create a custom host.
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8. Thank You...