Autonomous system (Internet)

ASNs are assigned in blocks by the Internet Assigned Numbers Authority (IANA) to regional Internet registries (RIRs). The appropriate RIR then assigns ASNs to entities within its designated area from the block assigned by IANA. Entities wishing to receive an ASN must complete the application process of their RIR, LIR or upstream service provider and be approved before being assigned an ASN. Current IANA ASN assignments to RIRs can be found on the IANA website. RIRs, as part of NRO, can revoke AS numbers as part of their Internet governance abilities. There are other sources for more specific data: • APNIC: https://ftp.apnic.net/stats/apnic/ • RIPE NCC: https://ftp.ripe.net/ripe/stats/ • AFRINIC: https://ftp.afrinic.net/pub/stats/afrinic/ • ARIN: https://ftp.arin.net/pub/stats/arin/ • LACNIC: https://ftp.lacnic.net/pub/stats/lacnic/ ==ASN table==

A complete table of available 16-bit and 32-bit ASN: ==Types==

Autonomous systems (AS) can be grouped into four categories, depending on their connectivity and operating policy. • multihomed: An AS that maintains upstream or peering connections to more than one other AS. This allows the AS to remain connected to the Internet in the event of a complete failure of one of their connections. However, unlike a transit AS, this type of AS would not allow traffic from one AS to pass through on its way to another AS. • stub: An AS that is connected to only one other AS. This may be an apparent waste of an AS number if the network's routing policy is the same as its upstream AS's. However, the stub AS may have peering with other autonomous systems that is not reflected in public route-view servers. Specific examples include private interconnections in the financial and transportation sectors. • transit: An AS that acts as an intermediary between at least two ASes is called a transit. Since not all ASes are directly connected with every other AS, a transit AS carries data traffic between one AS to another AS to which it has links. == AS-SET ==

Autonomous systems can be included in one or more AS-SETs, for example AS-SET of RIPE NCC "AS-12655" has AS1, AS2 and AS3 as its members, but AS1 is also included in other sets in ARIN (AS-INCAPSULA) and APNIC (AS-IMCL). Other AS-SET sources can be RADB, LEVEL3 (tier 1 network now called Lumen Technologies) and also ARIN has the ARIN-NONAUTH source of AS-SETs. AS-SETs are created by network operators in an Internet Routing Registry (IRR), like other route objects, and can be included in other AS-SETs and even form cycles. AS-SET names usually start with "AS-", but can also have a hierarchical name. For example, the administrator of AS 64500 may create an AS-SET called "AS64500:AS-UPSTREAMS", to avoid conflict with other similarly named AS-SETs. Since early 2023, the RIPE NCC enforces hierarchical AS-SET names for new objects, due to issues with conflicts between different IRR databases and potential malicious use based on the AS-SET name. Other IRR databases have soon followed with the same restriction. AS-SETs are often used to simplify management of published routing policies. A routing policy is published in the IRR using "import" and "export" (or the newer "mp-import" and "mp-export") attributes, which each contain the source or destination ASN, and the ASN imported or exported. Instead of single ASNs, AS-SETs can be referenced in these attributes, which simplifies management of complex routing policies. ==See also==