Overview of ACL
Definition
As the name indicates, an Access Control List (ACL) is a list. The list contains matching clauses, which are actually matching rules and used to tell the device to perform action on the packet or not.
Purpose
ACLs are used to ensure reliable data transmission between devices on a network by performing the following:
- Defend the network against various attacks, such as attacks by using IP, Transmission Control Protocol (TCP), or Internet Control Message Protocol (ICMP) packets.
- Control network access. For example, ACLs can be used to control enterprise network user access to external networks, to specify the specific network resources accessible to users, and to define the time ranges in which users can access networks.
- Limit network traffic and improve network performance. For example, ACLs can be used to limit the bandwidth for upstream and downstream traffic and to apply charging rules to user requested bandwidth, therefore achieving efficient utilization of network resources.
Benefits
ACL rules are used to classify packets. After ACL rules are applied to a router, the router permits or denies packets based on them. The use of ACL rules therefore greatly improves network security.
An ACL is a set of rules. It identifies a type of packet but does not filter packets. Other ACL-associated functions are used to filter identified packets.