What does the term 'Autonomous System (AS)' refer to?

The term 'Autonomous System (AS)' refers to a collection of IP networks under a single organization's control. It is a significant concept in the context of the Internet and routing because an Autonomous System is essentially a group of IP networks and routers that fall under the control of a single administrative entity. This entity is often responsible for managing the routing policies and for the management of IP address allocation.

An Autonomous System is identified by a unique number known as an Autonomous System Number (ASN), which is crucial for routing protocols, especially Border Gateway Protocol (BGP), where AS numbers help maintain a clear structure of the Internet's routing architecture. By grouping multiple networks, an AS can implement policies that ensure efficient data routing and control over how traffic routes through its networks to and from other Autonomous Systems.

Understanding the concept of an Autonomous System is fundamental for routing specialists as it directly influences how data is exchanged over the Internet and how routing decisions are made between different networks.