WindowsIdentity works on my pc but not on my webserver

What am I missing on my webserver for the following code to work? Currently the webserver shows, "IIS APPPOOL\DefaultAppPool" as the returned result. On my pc it works, I see my windows authenication user login.
Both my pc and with web server have Anonymous Authentication disabled and Windows Authentication is set to enabled.
 
System.Security.Principal.WindowsIdentity currentUser = System.Security.Principal.WindowsIdentity.GetCurrent();
Session["CurrentUser"] = currentUser.Name;
                <h1>
                    <% =Session["CurrentUser"] %>, welcome
                </h1>
...