GlobalNames zone is used on Windows Server 2008 DNS servers to provide single name support for static resources that cannot utilize DNS. It is an upgrade mitigation strategy designed to help organizations move away from WINS. To allow for the GlobalNames zone to be functional, all authorative DNS servers must be running Windows Server 2008. Your domain controllers do not need to be running Windows Server 2008, only the DNS servers. For that reason, a funcation level of 2003 will allow the GlobalNames zone to be functional.