An autonomous system (AS) is a collection of IP networks and routers controlled by a single organization or entity that follows a unified routing policy. Each AS is identified by a unique Autonomous System Number (ASN) and is responsible for routing data within its network and between other ASes. Autonomous systems communicate with each other using the Border Gateway Protocol (BGP) to ensure the efficient flow of information across the Internet.


Types of Autonomous Systems:


Single-homed AS: An AS that connects to the internet through only one connection to another AS.

Multi-homed AS: An AS connected to the internet through multiple connections to different ASes, ensuring redundancy and improved reliability.

Transit AS: An AS that allows data to pass through its network to reach other ASes. These are typically larger ISPs or backbone providers.

Stub AS: An AS that only connects to one other AS, often used by smaller organizations or businesses.