What is an autonomous system (AS)?

Last Updated: March 13, 2023

An Autonomous System (AS) is a collection of connected Internet Protocol (IP) networks, routers, and other network equipment that is administered and operated by a single organization or entity. An AS is defined by a unique number called an Autonomous System Number (ASN), which is assigned by the Internet Assigned Numbers Authority (IANA).

An AS is responsible for routing traffic within its network and exchanging traffic with other autonomous systems. ASes use various routing protocols, such as Border Gateway Protocol (BGP), to exchange routing information and determine the most efficient path for traffic to take between networks.

ASes are used by internet service providers (ISPs), large corporations, and government agencies to manage their own networks and exchange traffic with other networks. ASes also play a critical role in the operation of the internet as a whole, as they form the backbone of the global routing system that allows traffic to flow across the internet.