Autonomous System Number (ASN)

What is Autonomous System Number (ASN)

An Autonomous System (AS) is a group of networks that are controlled and managed by a single entity, such as an Internet Service Provider (ISP). An Autonomous System Number (ASN) is a unique number assigned to an AS by a regional Internet registry (RIR) to identify the AS on the Internet.

ASNs are used in the Border Gateway Protocol (BGP), which is a routing protocol used to exchange routing and reachability information between ASs. When two ASs communicates with each other using BGP, they exchange information about the networks that they control, and the ASN is used to identify the AS that owns each network.

ASNs are important because they allow the Internet to operate as a decentralized network, where different ASs can control their own networks and make routing decisions independently. This allows for flexibility and scalability in the Internet, as new networks can be added and routing decisions can be made based on local policies.

ASNs are assigned by RIRs, which are organizations that are responsible for allocating Internet resources in a specific region of the world. There are five RIRs: AfriNIC (Africa), APNIC (Asia Pacific), ARIN (North America), LACNIC (Latin America and the Caribbean), and RIPE NCC (Europe, the Middle East, and parts of Central Asia).

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