Just like its predecessors, SQL Server 2005 still supports Windows and Mixedauthentication modes. In the Windows Authentication Mode, access is grantedbased on a security token assigned during successful domain (or local server) logonby a Windows account, which subsequently requests access to SQL Serverresources. In this case, such accounts must belong to the same Windowsenvironment as the computer hosting SQL Server (this environment can consist ofany combination of trusted domains or forests). In the Active Directory domainenvironment, an additional level of protection is provided by Kerberos protocol,which governs the behavior of the Windows authentication mechanism (on Windows2003 Server based-clusters, Kerberos authentication can be used against SQLServer 2005 virtual servers). The Mixed Authentication Mode also allows SQLServer Authentication (in addition to Windows Authentication), which relies on theverification of credentials stored and maintained by the SQL Server. Due toincreased security and no need for a separate set of accounts (since existingWindows users and groups are leveraged), Windows Authentication is the preferredoption; however, security of SQL Server based logins has improved through itsencryption with SQL generated certificates, as long as communication involves thenew MDAC client software, based on .NET provider.