IP Address Space and Autonomous System Numbers (ASN)

The Internet Assigned Numbers Authority (IANA) delegates the allocation of internet number resources, including IP address space and Autonomous System Numbers (ASNs), to the Regional Internet Registries (RIRs). There are currently five RIRs: ARIN, LACNIC, RIPE NCC, AFRINIC, and APNIC.

Regional Internet Registries may manage IP address space and ASNs directly, or delegate that responsibility to a National Internet Registry (NIR).

For example, in India, registry responsibilities have been delegated to the Indian Registry for Internet Names and Numbers (IRINN), available at https://www.irinn.in.

Each Autonomous System is assigned a unique Autonomous System Number for use with Border Gateway Protocol (BGP) routing. This makes it possible to identify each network on the internet uniquely.

An Autonomous System is a collection of connected IP routing prefixes under the control of one or more network operators. It represents a single administrative organization or domain that presents a clearly defined routing policy to the internet.