How is ACL used in Telecom?
ACL stands for Access Control List, it is a “table” that tells a computer operating system which access rights each user has to a particular system object. For example if he can access a file directory or individual file (each object has a security attribute that identifies its access control list).
In Telecom is used as a set of rules for filtering network traffic.
The main idea of using an ACL is to provide security to your network. Without it, any traffic is either allowed to enter or exit, making it more vulnerable to unwanted and dangerous traffic.
In a nutshell, it acts as the gatekeeper of the network regulating all incoming and outgoing data packets. It works according to set rules and checks all incoming and outgoing data to determine whether it complies with these rules.
An ACL is the same as a Stateless Firewall, which only restricts, blocks, or allows the packets that are flowing from source to destination.
ACLs are the packet filters of a network. They can restrict, permit, or deny traffic which is essential for security. An ACL allows you to control the flow of packets for a single or group of IP address or different for protocols, such as TCP, UDP, ICMP, etc.
Types can be Standard ACL (check source address), Extended ACL (check both source and destination), Dynamic ACL or Reflexive ACL.
Here is a nice article with good explanation: