Autonomous Systems

At the largest scale, the Internet is a collection of autonomous systems or AS. Large organisations and ISPs will register as an AS and receive a globally unique autonomous system number (ASN). All the IP address ranges assigned to the organisation are associated with the ASN. This structure allows addresses to be advertised to multiple places on the Internet simultaneously; each network on the Internet can make its way to the AS via the most economical path. This is a multi-homed AS. Some company’s primary business is as a carrier providing transit for other AS. Most countries and large cities will also have neutral exchange points, where everyone operating in that region can connect economically and at high speed. For Ireland, look up the INEX [1]