What is IANA?

IANA (Internet Assigned Numbers Authority) coordinates the internet's global registries: IP address and AS number pools, the DNS root zone and protocol numbers.

IANA sits at the top of the number hierarchy and hands out large blocks rather than serving individual networks. For IP addresses and ASNs, it allocates blocks to the five Regional Internet Registries, which in turn allocate to ISPs, organisations and local registries in their region. IANA's free pool of IPv4 ran out in 2011, when the last /8 blocks were handed to the RIRs; IPv6 space is handed out in much larger blocks from 2000::/3. IANA also maintains the DNS root zone, the list of top-level domains and the nameservers for each, and it keeps the registries of protocol parameters that the IETF defines in RFCs, such as TCP and UDP port numbers, IP protocol numbers, BGP attribute codes and ICMP types. IANA is a function of ICANN, carried out since 2016 by its affiliate Public Technical Identifiers (PTI).

Engineers meet IANA mostly through its registries. When you want to know what port 179 is assigned to (BGP), which ranges are reserved for documentation, or what a BGP path attribute code means, the IANA registry is the authoritative list. The special-purpose address registries are especially useful: they record ranges such as 10.0.0.0/8 for private use and 192.0.2.0/24 and 2001:db8::/32 for documentation. A common confusion is thinking IANA gives addresses to companies directly. It doesn't: you get addresses and ASNs from your RIR (or an ISP), and IANA only deals with the RIRs. The BGP Fundamentals lesson shows how ASN ranges are split between public, private and documentation use.