Classic Mode:
This
is nothing but Windows Authentication. If any web application is created with
Classic Mode Authentication then it cannot applicable to configure forms based
authentication. But, to configure this application to use Forms Based
Authentication then you can convert from Classic Mode to Claims Based.
But,
there is no UI exist for doing this conversion. The only way around is through
PowerShell.
$app = get-spwebapplication "URL"
$app.useclaimsauthentication = "True"
$app.Update()
But, if an application is created using Claims based
and if you want to convert from Claims based to Classic Mode then it is not
possible either through UI or through PowerShell. So, remember this.
Claims Based:
In SharePoint 2010 for a web application we can enable both windows, forms authentication.
In earlier implementation to do this, we have to create two web applications
which has different zones and different authentication. But, with the new
claims based authentication a single application can have the capability to
configure both windows and forms under single URL. All this is possible because
of the authentication framework is built on Microsoft Identify Foundation. And
it uses “Geneva” framework to handle this authentication.
