Autonomous System - Networking
On the Internet, an autonomous system (AS) is the unit of router policy, either a single network or a group of network that is controlled by a common network administrator (or group of administrators) on behalf of a single administrative entity (such as a university, a business enterprise, or a business division). An autonomous system is also sometimes referred to as a routing domain. An autonomous system is assigned a globally unique number, sometimes called an Autonomous System Number (ASN).
Networks within an autonomous system communicate routing information to each other using an Interior Gateway Protocol (Interior Gateway Protocol). An autonomous system shares routing information with other autonomous systems using the Border Gateway Protocol (Border Gateway Protocol). Previously, the Exterior Gateway Protocol (Exterior Gateway Protocol) was used. In the future, the BGP is expected to be replaced with the OSI Inter-Domain Routing Protocol (IDRP).