Access control list (ACL)
Is a list that specifies which users, groups, or system processes are granted access to specific system object such as programs, processes or files.
An ACL includes permissions such as read, write, execute. In modern implementations, ACL also manage groups and inheritance in a hierarchy of groups. So "modern ACLs" can express all that RBAC express, and are notably powerful (compared to "old ACLs") in their ability to express access control policy in terms of the way in which administrators view organizations.
On routers and switches in particular, 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. Both individual servers as well as routers can have network ACLs. Access control lists can generally be configured to control both inbound and outbound traffic, and in this context they are similar to firewalls.