Autonomous systems

Autonomous systems 

6.2.2

This page will define an autonomous system (AS).
An AS is a collection of networks under a common administration that share a common routing strategy. To the outside world, an AS is viewed as a single entity. The AS may be run by one or more operators while it presents a consistent view of routing to the external world.
The American Registry of Internet Numbers (ARIN), a service provider, or an administrator assigns a 16-bit identification number to each AS. This autonomous system number is a 16 bit number. Routing protocols, such as Cisco IGRP, require the assignment of a unique, AS number.
The next page will explain the purpose of routing protocols and autonomous systems.