An Autonomous System (AS) is a group of IP address networks managed by one or more network operators having a unique, clear routing policy.

Each Autonomous System (AS) has an associated number that is used as an identifier of the Autonomous System for exchanging external routing information. Exterior routing protocols, such as BGP, are used for exchanging routing information among Autonomous Systems.
The term "Autonomous System" is frequently misinterpreted as merely a convenient way to group networks that are under the same management. However, if there is more than one routing policy in the group, more than one AS is necessary. On the other hand, if the group of networks has the same policy as the other groups, they fall within the same AS regardless of management structure. Thus, by definition, all networks that make up an Autonomous System share the same routing policy.

In order to simplify global routing tables, a new Autonomous System Number (ASN) should only be issued when a new routing policy is necessary. Sharing the same ASN among a group of networks that are not under the same management will require additional coordination among network administrators and, in some cases, will require redesigning the network to a certain degree. However, this is probably the only way to implement the desired routing policy.

LACNIC shall assign Autonomous System Numbers to those organizations that meet the following requirements:

1.The organization must be multi-homed with two or more independent Autonomous Systems at the time of application, or planning to become multi-homed within a period of no more than two weeks as of the moment of application. An organization is considered multi-homed if it receives Internet connectivity without restrictions from more than one Internet Service Provider.

2.The organization must submit detailed documentation describing the applicant's routing policy, which must be unique and different to that applied by the ASN to which it is connected. This documentation must include the exterior routing protocol to be used, IP addresses that will conform the AS and a detailed explanation of the reasons why its routing policy differs from that of its providers.

It is the obligation of the organization receiving an Autonomous System Number from LACNIC to maintain updated records of postal addresses and points of contact.

In LACNIC's WHOIS system it is possible to represent up to three different points of contact, namely:

owner-c, which represents the administrative contact of the organization to which the ASN was assigned;

routing-c, contact that, through the IP and ASN administration system, may register the routing policies adopted by the Autonomous System;

abuse-c, security contact (Abuse Contact).