 Windows 2000 then extended the syntax for access control entries such that they could not only grant or deny access to entire LDAP objects, but also to individual attributes within these objects.On some types of proprietary computer-hardware (in particular routers and switches), an access-control list provides rules that are applied to port numbers or IP addresses that are available on a host or other layer 3, each with a list of hosts and/or networks permitted to use the service.Although it is additionally possible to configure access-control lists based on network domain names, this is a questionable idea because individual TCP, UDP, and ICMP headers do not contain domain names.