AJAX Basics

ASP.NET AJAX enables you to take full advantage of the capabilities of the browser to deliver richer Web experiences that work on any modern browser
ASP.NET AJAX enables ASP.NET developers to enrich their existing Web applications with incredible ease

ASP.NET AJAX makes it possible to easily take advantage of AJAX techniques on the Web and enables you to create ASP.NET pages with a rich, responsive UI, and server communication. However, ASP.NET AJAX isn’t just for ASP.NET development. You can take advantage of the rich client framework to easily build client-centric Web applications that integrate with any backend data provider.

How AJAX works.....

So here is AJAX architecture for your better understandig..

AJAX - What's the buzz all about?

In the era of high-tech words buzzing around - there is a chance you might have come across AJAX. Surely, AJAX is one of the technologies that are being widely adopted and used. At first glance, you might be thinking:

What is AJAX?

I am not just going to say it stands for Asynchronous Javascript And XML... If you have worked over web applications (or atleast have used one), for each dynamic content to be fetched from web server, you need to make a call to a specific page. The call (or request) in return, sends you a complete page (response). Traditionally, it would refresh or reload a webpage for each new request. Simply put forward, you click a link, you make a request and you wait for the server to respond. This is called the "call-and-response" interaction model. AJAX, as a down-to-earth intro, is a technique in which your web application interacts with your web server - 'behind the scenes'. This means, while you are viewing a web-page - it is 'silently' posting and retrieving data from the webserver without letting you know (i.e. without refreshing the page). This is the AJAX-way of interacting.

why are we so hearing about ajax these days?

Well, the basic fact, AJAX is a 'technique', and not a 'new' tool. The technique is based on simple JavaScript and XML usage - which has been around since 1997-98. This approach has recently came in a more wider 'public' view after it was used 'extensively' in G-mail (an ajax-based web-mail client)

Conclusion

AJAX makes applications behave similar to that of a desktop application. A bridge between web-apps and desktop-apps, you might say. With javascript and xml combined, possibilities are end-less - which are yet to be exploited to its fullest.

Key Benefits of .NET Framework

ASP.NET :- simplify browser-based development

ADO.NET :- a more powerful model for data access

Deployment :- simpler, safer

Class library :-common routines

Web services :- new approach to providing computing functionality over the Internet

dot net architecture in depth

Here is more descriptive architecture

ASP.net Architecture

This section provides an overview of the ASP.NET infrastructure and subsystemrelationships, as they relate to the subject of security. The following illustration shows the relationships among the security systems in ASP.NET.

As the illustration shows, all Web clients communicate with ASP.NET applications through IIS. IIS deciphers and optionally authenticates the request. If Allow Anonymous is turned on, no authentication occurs. IIS also finds the requested resource ( such as an ASP.NET application ), and, if the client is authorized, returns the appropriate resource.
In addition to the built-in ASP.NET security features, an ASP.NET application can use the low-level security features of the .NET Framework.
Integrating with IIS
This release of ASP.NET uses IIS 5.0 as the primary host environment. When considering ASP.NET authentication, you should understand the interaction with IIS authentication services.
IIS always assumes that a set of credentials maps to a Windows NT account and uses them to authenticate a user. There are three different kinds of authentication available in IIS 5.0: basic, digest, and Integrated Windows Authentication ( NTLM or Kerberos ). You can select the type of authentication to use in the IIS administrative services.
If you request a URL containing an ASP.NET application, the request and authentication information are handed off to the application.